Journal articles on the topic 'Triple phase boundary (TPB)'
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1
Wakamatsu, Katsuhiro, Takaaki Yasuda, Yuji Okada, and Teppei Ogura. "First-Principles Studies for Optimal Model of the Ni/YSZ Triple Phase Boundary in Solid Oxide Cells." ECS Transactions 111, no. 6 (May 19, 2023): 1333–46. http://dx.doi.org/10.1149/11106.1333ecst.
Abstract:
To resolve the existing issues of solid oxide cells such as degradation and efficiency improvement, it is essential to understand reaction mechanisms on the surface/interface such as triple phase boundary (TPB) as a highly active site that consists of catalysts, electrolytes, and gas phases. However, the reliable TPB model has not been still uniquely defined to discuss the property. In this study, we have focused on the TPB model comprising Ni catalysts, yttria-stabilized zirconia (YSZ) electrolytes, and gas phases and aimed to theoretically identify a reliable TPB model. In concrete, we identified firstly the stable structure of YSZ surface models by using density functional theory calculations considering different oxygen vacancy positions, yttrium atom arrangements, yttria concentration, and YSZ surfaces. Thereafter, we discussed a reliable Ni/YSZ interface model based on our proposed YSZ model by evaluating different Ni structure types, Ni interfaces in contact with the YSZ surface, and interface positions.
2
Zhang, Shidong, Kai Wang, Shangzhe Yu, Nicolas Kruse, Roland Peters, Felix Kunz, and Rudiger-A. Eichel. "Multiscale and Multiphysical Numerical Simulations of Solid Oxide Cell (SOC)." ECS Transactions 111, no. 6 (May 19, 2023): 937–54. http://dx.doi.org/10.1149/11106.0937ecst.
Abstract:
This study presents a novel model for investigating the microstructural evolution of nickel (Ni), yttria-stabilized zirconia (YSZ), and gas phases in a solid oxide cell (SOC), and its effects on cell performance. The triple-phase-boundary (TPB), which is the interface between the three phases, plays a crucial role in the electrochemical reaction of the SOC. However, during operation, nickel particles coarsen or migrate, leading to the redistribution of the TPB. To study this phenomenon, a phase field method was utilized to simulate the fuel electrode's detailed structure, and an approach was developed to track the TPB lines (TPBl) and voxels (TPBv). The study then employed the open-source computational fluid dynamics library, OpenFOAM, to simulate the half-cell performance. The results provide a detailed understanding of the dynamics of the TPB and its impact on multiphysical transport phenomena.
3
Putri, Rihan Amila, Dani Gustaman Syarif, and Atiek Rostika Noviyanti. "Correlation Microstructure of Triple Phase Boundary and Crystallinity in SOFC Cells NiO/LSGM/LCM." Research Journal of Chemistry and Environment 26, no. 8 (July 25, 2022): 44–50. http://dx.doi.org/10.25303/2608rjce044050.
Abstract:
The electrochemical process in the TPB microstructure depends on the conductivity of the SOFC cell constituent materials. Electrolyte and electrode materials must have good conductivity. The crystallinity of an electrolyte can affect its conductivity. In this study, the electrolyte La0.8Sr0.2Ga0.8Mg0.2O3–δ (LSGM) was used and is known to have good conductivity at intermediate temperatures. The single cell of LSGM electrolyte with La0.7Ca0.3MnO3 (LCM) cathode which has high electronic conductivity and NiO anode which has low area-specific resistance (ASR) is expected to produce compatible cells. The production of NiO/LSGM/LCM cells was carried out through the solid-solid phase synthesis method. Microstructural analysis of TPB was performed using SEM-EDS; meanwhile, crystallinity was obtained through XRD analysis. The crystallinity values of NiO, LSGM and LCM cell components above 80% allow the cells to produce high conductivity with a three-phase boundary microstructure from porous electrodes and relatively dense electrolytes which can increase the possibility of gas, ion and electron encounters in the TPB. In SOFC NiO/LSGM/LCM cells, Ni=11.08%; Ca=6.84%; Mn=9.28% and no precipitate is formed at the electrolyte-electrode boundary, so that the electrochemical process on the TPB microstructure could run well.
4
Rix, Jillian G., Boshan Mo, Alexey Y. Nikiforov, Uday B. Pal, Srikanth Gopalan, and Soumendra N. Basu. "Quantifying Percolated Triple Phase Boundary Density and Its Effects on Anodic Polarization in Ni-Infiltrated Ni/YSZ SOFC Anodes." Journal of The Electrochemical Society 168, no. 11 (November 1, 2021): 114507. http://dx.doi.org/10.1149/1945-7111/ac3599.
Abstract:
Increasing the density of percolated triple phase boundaries (TPBs) by infiltrating nanoscale electrocatalysts can improve the performance of solid oxide fuel cell (SOFC) anodes. However, the complex microstructure of these infiltrated nanocatalysts creates challenges in quantifying their role in anode performance improvements. In this research, scanning electron microscopy of fractured cross-sections of a Ni-nanocatalyst infiltrated anodic symmetric cell along with three-dimensional (3-D) reconstruction of the same anode have been used to quantify the changes in percolated TPB densities due to infiltration. This change in percolated TPB density has been compared to the improvement in anode activation polarization resistance measured by electrochemical impedance spectroscopy (EIS). It was found that increased TPB densities only partially accounted for the measured performance improvement. Distribution of relaxation times (DRT) analyses showed that a reduction in the time constants of the catalytic processes in the anode also play a role, suggesting that the added nanoscale percolated TPB boundaries are more electrochemically active as compared to the cermet TPB boundaries.
5
Wilson, James R., Marcio Gameiro, Konstantin Mischaikow, William Kalies, Peter W. Voorhees, and Scott A. Barnett. "Three-Dimensional Analysis of Solid Oxide Fuel Cell Ni-YSZ Anode Interconnectivity." Microscopy and Microanalysis 15, no. 1 (January 15, 2009): 71–77. http://dx.doi.org/10.1017/s1431927609090096.
Abstract:
AbstractA method is described for quantitatively analyzing the level of interconnectivity of solid-oxide fuel cell electrode phases. The method was applied to the three-dimensional microstructure of a Ni–Y2O3-stabilized ZrO2 (Ni-YSZ) anode active layer measured by focused ion beam scanning electron microscopy. Each individual contiguous network of Ni, YSZ, and porosity was identified and labeled according to whether it was contiguous with the rest of the electrode. It was determined that the YSZ phase was 100% connected, whereas at least 86% of the Ni and 96% of the pores were connected. Triple-phase boundary (TPB) segments were identified and evaluated with respect to the contiguity of each of the three phases at their locations. It was found that 11.6% of the TPB length was on one or more isolated phases and hence was not electrochemically active.
6
Kong, Wei, Mengtong Zhang, Zhen Han, and Qiang Zhang. "A Theoretical Model for the Triple Phase Boundary of Solid Oxide Fuel Cell Electrospun Electrodes." Applied Sciences 9, no. 3 (January 31, 2019): 493. http://dx.doi.org/10.3390/app9030493.
Abstract:
Electrospinning is a new state-of-the-art technology for the preparation of electrodes for solid oxide fuel cells (SOFC). Electrodes fabricated by this method have been proven to have an experimentally superior performance compared with traditional electrodes. However, the lack of a theoretic model for electrospun electrodes limits the understanding of their benefits and the optimization of their design. Based on the microstructure of electrospun electrodes and the percolation threshold, a theoretical model of electrospun electrodes is proposed in this study. Electrospun electrodes are compared to fibers with surfaces that were coated with impregnated particles. This model captures the key geometric parameters and their interrelationship, which are required to derive explicit expressions of the key electrode parameters. Furthermore, the length of the triple phase boundary (TPB) of the electrospun electrode is calculated based on this model. Finally, the effects of particle radius, fiber radius, and impregnation loading are studied. The theory model of the electrospun electrode TPB proposed in this study contributes to the optimization design of SOFC electrospun electrode.
7
Wakamatsu, Katsuhiro, Takaaki Yasuda, Yuji Okada, and Teppei Ogura. "First-Principles Studies for Optimal Model of the Ni/YSZ Triple Phase Boundary in Solid Oxide Cells." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 207. http://dx.doi.org/10.1149/ma2023-0154207mtgabs.
Abstract:
Non-Faradaic electrochemical modification of catalytic activity (NEMCA) with electric field applications in solid oxide cells (SOCs) is thought to be induced by spillover effects of lattice oxygen from the bulk, although the detailed mechanism has not still been clear. In SOCs, important phenomena such as fuel decomposition, charge transfer, etc. occur at the triple phase boundary (TPB) as a highly active site that consists of catalyst, electrolyte, and gas phases. NEMCA is expected to be also induced strongly by the surface mechanism on TPB, and understanding surface reactions on TPB is essential for improving catalyst and cell performances. However, the reliable TPB model has not been still uniquely defined to discuss the property of TPB although various studies have been reported. Therefore, in this study, we have focused on the TPB model comprising Ni catalyst cluster; YSZ electrolyte; and gas phase, and aimed to identify a reliable TPB model for theoretical studies by using first-principles calculations as an initial step. In concrete, we identified firstly the stable structures of YSZ surface models by using DFT calculations taking into account oxygen vacancy positions, yttrium atom arrangements, yttria concentration, and other factors. Thereafter, we discussed a reliable Ni/YSZ interface model based on the most stable YSZ model proposed above results by evaluating the Ni structure, interface stability, and so on. In this study, DFT calculations with a plane-wave basis set were implemented using CASTEP, and GGA-PBE exchange-correlation functional was used. The plane-wave cutoff energy was set as 489.8 eV, the OTFG-ultrasoft was used as the pseudopotentials, and the spin-polarization is considered because YSZ is a ferromagnetic substance. In YSZ surface models, yttria concentrations are set to 4.35 mol% and 9.1 mol% which shows the maximum ion conductivity of ZrO2. The three-layer YSZ (111) slabs with 15 Å vacuum layer with 2×2 and 2×4 unit cells were used for repeated slab models. The DFT+U method is used to obtain the correct electric structure of metal oxides with partially filled d or f-orbital shells, and k-points were set to 4×2×1. In Ni/YSZ interface models, we considered Ni cluster and Ni belt type models based on the most stable 2×4 YSZ surface model (9.1 mol%) proposed in this study. We also considered both cases of (111) and (100) facets for the contact interface. In the case of Ni/YSZ interface models, the DFT+U method was not considered to improve the calculation convergence and k-points were set to 4×2×1. A schematic diagram of the Ni/YSZ interface model is shown in the attached Figure. In the case of the 2×2 YSZ model with the yttria concentration of 9.1 mol%, the YSZ model is stabilized when oxygen vacancy is on the second O atom layer and the second neighbor to Y atoms, indicating that improvement in the geometry instability of ZrO2 for 8-coordination is more important than keeping local electron neutrality. We have also found that oxygen vacancy positions are more sensitive to the YSZ surface stability than Y atom arrangements. In the case of the 2×4 YSZ model with the yttria concentration of 4.35 mol%, the YSZ model where there are Y atoms on the first layer is stabilized. The crystal structure achieves a more stable structure by varying bond lengths when Y3+ with the larger ionic radius is replaced with Zr4+. Therefore, the structure is easier to stabilize when the Y atom exists on the surface than in the bulk due to the higher degree of freedom of the Y atom. The most stable structure of the 2×4 YSZ model with the yttria concentration of 9.1 mol% given based on the above results is 0.18 eV more stable than the previously reported structure [1]. This is because the number of Y atoms on the first layer with the second neighbor from oxygen vacancy is larger than the previously reported structure. We evaluated then the structural stability of the Ni/YSZ interface model based on the above YSZ model. As a result, we have found that adhesion energy between Ni and YSZ is independent of the relative position of Ni atoms. In addition, the larger the number of Ni atoms is, the more stable the structure is. This is because the electronic property of Ni atoms approaches the metal as increasing the number of Ni atoms. Other results and a detailed discussion will be reported in our meeting publications (ECS Transactions) and the presentation. [1] M. Shishkin and T. Ziegler, Phys. Chem. Chem. Phys., 16, 1798-1808 (2014). Figure 1
8
Gao, Min, Cheng Xin Li, Ming De Wang, Hua Lei Wang, and Chang Jiu Li. "Influence of the Surface Roughness of Plasma-Sprayed YSZ on LSM Cathode Polarization in Solid Oxide Fuel Cells." Key Engineering Materials 373-374 (March 2008): 641–44. http://dx.doi.org/10.4028/www.scientific.net/kem.373-374.641.
Abstract:
Under SOFCs operating condition, the cathode reaction rate is determined by triple phase boundary (TPB) areas which are associated with the geometry of the interface between the cathode and the electrolyte. In this paper, YSZ electrolyte was deposited by atmospheric plasma spraying (APS). A nano-scaled lanthanum strontium manganate (LSM) cathode was prepared by sol-gel process on APS YSZ with different surface roughness to aim at increasing the TPB. The polarization curves of LSM cathode were characterized by potentiostat. The influence of the roughness of APS YSZ on the polarization of LSM cathode was investigated. It was found that the overpotential of the LSM cathode is significantly reduced with the increase of YSZ surface roughness.
9
Shaikh Abdul, Muhammed Ali, Ahmad Zubair Yahaya, Mustafa Anwar, Mun Teng Soo, Andanastuti Muchtar, and Vadim M. Kovrugin. "Effect of Synthesis Method of Nickel–Samarium-Doped Ceria Anode on Distribution of Triple-Phase Boundary and Electrochemical Performance." Crystals 11, no. 5 (May 6, 2021): 513. http://dx.doi.org/10.3390/cryst11050513.
Abstract:
Two-dimensional (2D) electron back scattered diffraction (EBSD) is a powerful tool for microstructural characterization of crystalline materials. EBSD enables visualization and quantification of the effect of synthesis methods on the microstructure of individual grains, thus correlating the microstructure to mechanical and electrical efficiency. Therefore, this work was designed to investigate the microstructural changes that take place in the Ni-SDC cermet anode under different synthesis methods, such as the glycine–nitrate process (GNP) and ball-milling. EBSD results revealed that different grain size and distribution of Ni and SDC phases considerably influenced the performance of the Ni–SDC cermet anodes. The performance of the Ni–SDC cermet anode from GNP was considerably higher than that of Ni-SDC from ball-milling, which is attributed to the triple-phase boundary (TPB) density and phase connectivity. Due to the poor connectivity between the Ni and SDC phases and the development of large Ni and SDC clusters, the Ni-SDC cermet anode formed by ball milling had a lower mechanical and electrical conductivity. Moreover, the Ni–SDC cermet anode sample obtained via GNP possessed sufficient porosity and did not require a pore former. The length and distribution of the active TPB associated with phase connectivity are crucial factors in optimizing the performance of Ni-SDC cermet anode materials. The single cell based on the Ni–SDC composite anode prepared through GNP exhibited a maximum power density of 227 mW/cm2 and 121 mW/cm2 at 800 °C in H2 and CH4, respectively.
10
Jeong, Davin, Yonghyun Lim, Hyeontaek Kim, Yongchan Park, and Soonwook Hong. "Silver and Samaria-Doped Ceria (Ag-SDC) Cermet Cathode for Low-Temperature Solid Oxide Fuel Cells." Nanomaterials 13, no. 5 (February 27, 2023): 886. http://dx.doi.org/10.3390/nano13050886.
Abstract:
This study demonstrated a silver (Ag) and samarium-doped ceria (SDC) mixed ceramic and metal composite (i.e., cermet) as a cathode for low-temperature solid oxide fuel cells (LT-SOFCs). Introducing the Ag-SDC cermet cathode for LT-SOFCs revealed that the ratio between Ag and SDC, which is a crucial factor for catalytic reactions, can be tuned by the co-sputtering process, resulting in enhanced triple phase boundary (TPB) density in the nanostructure. Ag-SDC cermet not only successfully performed as a cathode to increase the performance of LT-SOFCs by decreasing polarization resistance but also exceeded the catalytic activity of platinum (Pt) due to the improved oxygen reduction reaction (ORR). It was also found that less than half of Ag content was effective to increase TPB density, preventing oxidation of the Ag surface as well.
11
Jang, Seungsoo, Kyung Taek Bae, Dongyeon Kim, Hyeongmin Yu, Seeun Oh, Ha-Ni Im, and Kang Taek Lee. "Microstructural Analysis of Solid Oxide Electrochemical Cells via 3D Reconstruction Using a FIB-SEM Dual Beam System." ECS Transactions 111, no. 6 (May 19, 2023): 1265–69. http://dx.doi.org/10.1149/11106.1265ecst.
Abstract:
Solid oxide electrochemical cells (SOCs) have attracted increasing attention as energy conversion devices due to their high efficiency. The microstructures of SOCs play a critical role in their electrochemical performance, however, characterizing them is challenging due to their heterogeneous microstructure. This paper describes a quantitative analysis of SOC microstructures via 3D reconstruction technique using a focused ion beam-scanning electron microscope (FIB-SEM) dual beam system. The reconstructed SOC electrodes offer microstructural characteristics, including particle and pore size, tortuosity, connectivity, and triple-phase boundary (TPB) density. These in-depth analyses contribute to better understanding of the electrochemical behavior of SOCs.
12
Imperial, James Francis L., and Rinlee Butch M. Cervera. "Synthesis and Characterization of Porous NiO/YSZ Electrode Materials Using Different Pore Formers." Materials Science Forum 917 (March 2018): 83–87. http://dx.doi.org/10.4028/www.scientific.net/msf.917.83.
Abstract:
Solid oxide electrolysis cell (SOEC) cathodes require a good porosity and a fine microstructure in order to maximize the triple phase boundary (TPB) between electronic conductor, ionic conductor and the gas phase involved in the reaction. Nickel oxide and yttria stabilized zirconia (NiO/YSZ) composite, one of the most desired candidates for SOEC cathode material, is synthesized via the glycine-nitrate combustion process and mixed with corn starch and carbon black pore formers in order to observe how they modify its microstructure and porosity. XRD spectra indicate a distinct cubic phases of both NiO and YSZ. SEM micrographs were able to confirm that the addition of selected pore formers lead to an increase in porosities. Apparent and relative density measurements show that corn starch pore former produces the lowest density among the sintered pellets. EIS measurements revealed that samples with lower density also showed lower total conductivity.
13
Ruse, Cristina Mariana, Lily Ann Hume, Yudong Wang, Thomas C. Pesacreta, and Xiao-Dong Zhou. "Quantifying Microstructure Features for High-Performance Solid Oxide Cells." Materials 17, no. 11 (May 29, 2024): 2622. http://dx.doi.org/10.3390/ma17112622.
Abstract:
The drive for sustainable energy solutions has spurred interest in solid oxide fuel cells (SOFCs). This study investigates the impact of sintering temperature on SOFC anode microstructures using advanced 3D focused ion beam–scanning electron microscopy (FIB-SEM). The anode’s ceramic–metal composition significantly influences electrochemical performance, making optimization crucial. Comparing cells sintered at different temperatures reveals that a lower sintering temperature enhances yttria-stabilized zirconia (YSZ) and nickel distribution, volume, and particle size, along with the triple-phase boundary (TPB) interface. Three-dimensional reconstructions illustrate that the cell sintered at a lower temperature exhibits a well-defined pore network, leading to increased TPB density. Hydrogen flow simulations demonstrate comparable permeability for both cells. Electrochemical characterization confirms the superior performance of the cell sintered at the lower temperature, displaying higher power density and lower total cell resistance. This FIB-SEM methodology provides precise insights into the microstructure–performance relationship, eliminating the need for hypothetical structures and enhancing our understanding of SOFC behavior under different fabrication conditions.
14
Sozal, Md Shariful Islam, Wenhao Li, Suprabha Das, Borzooye Jafarizadeh, Azmal Huda Chowdhury, Andriy Durygin, Vadym Drozd, Chunlei Wang, and Zhe Cheng. "Fabrication and Electrochemical Testing of Silver Pattern Cathodes for Proton Conducting It-SOFC." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 139. http://dx.doi.org/10.1149/ma2023-0154139mtgabs.
Abstract:
Dense silver (Ag) cathodes with different triple phase boundary (TPB; the interface of gas, electrolyte and electrode) length (LTPB) and electrode area (AELT) were fabricated by photolithography and E-beam evaporation over different proton-conducting electrolytes such as BaZr0.4Ce0.4Y0.1Yb0.1O3– δ (BZCYYb4411). A bi-layer lift-off resist method appears more versatile than single layer for successful pattern cathode fabrication. The electrochemical behaviors of Ag pattern cathodes over the BZCYYb4411 electrolyte were tested with counter electrode such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ and correlated against geometric features such as LTPB and AELT to understand the oxygen reduction kinetics and mechanism for proton conducting solid oxide fuel cells. Figure 1
15
Lei, Yinkai, Tianle Cheng, Tao Yang, William K. Epting, Harry W. Abernathy, and You-Hai Wen. "Modeling the Distribution of Oxygen Partial Pressure in the Electrolyte of Solid Oxide Cells and Its Implication on Microstructure Evolution in the Hydrogen Electrode." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 148. http://dx.doi.org/10.1149/ma2023-0154148mtgabs.
Abstract:
The distribution of oxygen partial pressure in the electrolyte has an important effect on the stability of solid oxide cells (SOCs). It is well known that the high oxygen partial pressure at the oxygen electrode and electrolyte interface causes delamination, while its effect in the hydrogen electrode (HE) has received comparatively little attention. The only existing model for the distribution of oxygen partial pressure in the electrolyte of SOC is proposed by Virkar et al., which is a one-dimensional model that does not consider the Butler-Volmer equation at triple phase boundary (TPB) nor the microstructure’s effect. In this work, the Virkar’s model was extended to three dimensions and the Butler-Volmer equation was added at TPB to investigate the distribution of oxygen partial pressure in the actual electrode microstructure. The oxygen partial pressure in the YSZ phase of HE near the HE-electrolyte interface was found to be significantly greater than the oxygen partial pressure in the pore phase of HE, which may lead to Ni oxidation. Furthermore, a phase field model was employed to simulate the microstructural evolution of Ni particles on YSZ surfaces with the assumption that NiO forms at the Ni-YSZ interface. The NiO formation affects the microstructure evolution in HE by changing the shape of the Ni particles.
16
Lei, Yinkai, Tianle Cheng, Tao Yang, William K. Epting, Harry W. Abernathy, and You-Hai Wen. "Modeling the Distribution of Oxygen Partial Pressure in the Electrolyte of Solid Oxide Cells and Its Implication on Microstructure Evolution in the Hydrogen Electrode." ECS Transactions 111, no. 6 (May 19, 2023): 965–76. http://dx.doi.org/10.1149/11106.0965ecst.
Abstract:
The distribution of oxygen partial pressure in the electrolyte has an important effect on the stability of solid oxide cells (SOCs). It is well known that the high oxygen partial pressure at the oxygen electrode and electrolyte interface causes delamination, while its effect in the hydrogen electrode (HE) has received comparatively little attention. The only existing model for the distribution of oxygen partial pressure in the electrolyte of SOC is proposed by Virkar et al., which is a one-dimensional model that does not consider the Butler-Volmer equation at triple phase boundary (TPB) nor the microstructure’s effect. In this work, the Virkar’s model was extended to three dimensions and the Butler-Volmer equation was added at TPB to investigate the distribution of oxygen partial pressure in the actual electrode microstructure. The oxygen partial pressure in the yttria-stabilized-zirconia (YSZ) phase of HE near the HE-electrolyte interface was found to be significantly greater than the oxygen partial pressure in the pore phase of HE, which may lead to Ni oxidation. Furthermore, a phase field model was employed to simulate the microstructural evolution of Ni particles on YSZ surfaces with the assumption that NiO forms at the Ni-YSZ interface. The NiO formation affects the microstructure evolution in HE by changing the shape of the Ni particles.
17
Chou, Chen Chia, Chun Feng Huang, Firman Mangasa Simanjuntak, and Ying Ying Wu. "Electrospinning Processing and Microstructural Characterization of Ce0.78Gd0.2Sr0.02O2-δ Fiber for a Composite Anode." Advanced Materials Research 287-290 (July 2011): 2489–93. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2489.
Abstract:
Fabrication of a fiber anode with a mixture of the Gd2O3 and SrO co-doped ceria fibers and the Ni nano-catalyzer by using electrospinning and impregnated process were carried out for application in an intermediate temperature fuel cell (ITFC). Experimental results demonstrate that a uniform co-doped ceria fiber of 100 nm diameter could be spun at the concentration of PVP approximately 11.32 wt.% and electric field of 20 kV. The anodic films were prepared via a nickel wet dipping process and sintered at different temperatures. The micrograph of the anode sintered at 1200°C for1hr has a well defined microstructure in terms of electrolyte area covered with nickel and the triple phase boundary (TPB) between electrolyte, electrode and gas phase. Fiber anode exhibits low polarization resistance and high exchange current density due to formation of the reticular nano-fiber structure. Accordingly, using a new concept of combination of the nano-ceramic fiber and the Ni nano-particle for increasing the catalytic properties of anode is successfully proved, it is found that nano-fiber substituting to powder in anode could decrease the processing temperature of cell and maintain the porous structure of anode to increase the amount of TPB and restrain formation of agglomerates of nickel particles.
18
Bang, Sehee, Jongseo Lee, and Wonyoung Lee. "Highly Connected Oxygen Ion Conduction Pathways for Solid Oxide Fuel Cells Operating in Intermediate Temperatures with Fuel Flexibility." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 10. http://dx.doi.org/10.1149/ma2023-015410mtgabs.
Abstract:
Solid oxide fuel cells are promising eco-friendly power generating devices directly utilizing various fuels such as hydrogen, methane, and carbon dioxide. However, a technical breakthrough is required for further commercialization by lowering the high operating temperature to the intermediate temperature regime. Introducing the anode functional layer (AFL) between the electrolyte and anode is one of the crucial methods in the development of high performance solid oxide fuel cells by maximizing the triple phase boundary (TPB) sites. To activate the TPB sites, ensuring the continuous oxygen ion conduction from the electrolyte to the TPB sites is essential to maximize their utilization for hydrogen oxidation reactions (HORs). In this study, we modify the connectivity of oxygen ion conduction pathways in the AFL by controlling the microstructure in AFLs. We calculated active reaction site using image processing of cross-sectional scanning electron microscopy (SEM) image and the strong correlation between the electrochemical performance and calculated active reaction site is revealed. The modified AFL with highly connected oxygen ion conduction pathways exhibits substantially higher maximum power density (MPD) compared with conventional AFL: ~1.7-fold higher MPD of 1.51 Wcm-2 at 550 ℃ with hydrogen and ~3.5-fold higher MPD of 1.11 Wcm-2 at 550 ℃ with methane and carbon dioxide, surpassing previously reported values. Moreover, excellent carbon tolerance is observed in the modified AFL, exhibiting nearly no degradation at 550 ℃ for 130 h. This result substantiates the role of connectivity of the oxygen ion conduction pathways in the HOR and carbon tolerance in AFLs. Figure 1
19
Liu, Zerui, Jixin Shi, Yuqing Wang, Yixiang Shi, and Ningsheng Cai. "NH3-Fed Patterned Electrode Solid Oxide Fuel Cell: Experimental Performance Characterization and Elementary Reaction Modeling." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 342. http://dx.doi.org/10.1149/ma2023-0154342mtgabs.
Abstract:
Ammonia-fueled solid oxide fuel cells (SOFCs) have attracted the focus of researchers due to the feature of no carbon emission. Understanding the reaction mechanism is vital for the design and optimization of NH3-fed SOFCs. However, the catalytic decomposition reactions involved in porous electrodes led to the difficulty to distinguish the anode reaction mechanism. In the present study, we utilized a patterned anode to get a designed triple phase boundary (TPB) and avoid the effects of porous electrodes. In the performance test, we found that the current density of the NH3-fed SOFC was approximately 20% of that of the H2-fed SOFC under a similar working position at 750℃. The difference may mainly resulted from the limit of catalytic decomposition of NH3 caused by the narrow reactive area in the patterned electrode. A one-dimensional elementary reaction model was further developed to validate this hypothesis and to provide additional evidence for the reaction mechanisms of the NH3-fed SOFC.
20
Liu, Zerui, Jixin Shi, Yuqing Wang, Yixiang Shi, and Ningsheng Cai. "NH3-Fed Patterned Electrode Solid Oxide Fuel Cell: Experimental Performance Characterization and Elementary Reaction Modeling." ECS Transactions 111, no. 6 (May 19, 2023): 2189–202. http://dx.doi.org/10.1149/11106.2189ecst.
Abstract:
Ammonia-fueled solid oxide fuel cells (SOFCs) have attracted the focus of researchers due to no carbon emissions in utilization. Understanding the reaction mechanism is vital for the design and optimization of NH3-fed SOFCs. However, the catalytic decomposition reactions involved in porous electrodes led to difficulty in distinguishing the anode reaction mechanism. In the present study, we utilized a patterned anode to obtain a designed triple phase boundary (TPB) and avoid the effects of porous electrodes. In the performance test, we found that the exchange current density of the NH3-fed SOFC was approximately 5% of that of the H2-fed SOFC under a similar working position at 700℃. The difference may mainly result from the limit of catalytic decomposition of NH3 caused by the narrow reactive area in the patterned electrode. A one-dimensional elementary reaction model was further developed to validate this hypothesis and to provide additional evidence for the reaction mechanisms of the NH3-fed SOFC.
21
Cheng, Kun, Xiaobo Liu, Wenqiang Li, Zongkui Kou, and Shichun Mu. "Enhancing the Specific Activity of Metal Catalysts Toward Oxygen Reduction by Introducing Proton Conductor." Nano 11, no. 05 (April 25, 2016): 1650055. http://dx.doi.org/10.1142/s1793292016500557.
Abstract:
Enhancing oxygen reduction reaction (ORR) activity and simultaneously reducing usage of noble metal catalysts are significantly important both in fundamental and applied science communities for polymer electrolyte fuel cells (PEFCs). In this work, we confirm the proton conductor (perfluorosulfonic acid, containing [Formula: see text]SO3H) can promote the specific activity [Formula: see text] of metal catalysts toward ORR. Herein, Pt nanoparticles (NPs) with a small and narrow size distribution are encapsulated with perfluorosulfonic acid through a simple colloidal route. The resulting catalyst obtains about two times [Formula: see text] towards ORR than that of the pristine Pt/C. Significantly, the amount of [Formula: see text]SO3H groups is controlled by a heat-treatment method to investigate the influence of [Formula: see text]SO3H groups on [Formula: see text]. The results evidence the contribution of [Formula: see text]SO3H groups to elevating the ORR specific activity. The mechanism can be ascribed to the [Formula: see text]SO3H groups which effectively promote the transfer process of reaction species (e.g., H[Formula: see text], H2O), improving the triple-phase boundary (TPB).
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Sato, Kazuyoshi, Masayasu Uemura, Akira Kondo, Hiroya Abe, Makio Naito, and Kiyoshi Nogi. "Microstructural Control of Composite Anode for Anode Supported Intermediate Temperature Solid Oxide Fuel Cells." Advances in Science and Technology 45 (October 2006): 1869–74. http://dx.doi.org/10.4028/www.scientific.net/ast.45.1869.
Abstract:
Appropriate mechanical milling in dry ambient can improve the mixing state of two powder materials as well as produce their composite particles. In this study the influences of milling on microstructure and performance of anode supported SOFCs was investigated. First, NiO and YSZ powder mixture was milled using an attrition type apparatus for 5 and 30 min. The SOFCs were made through conventional ceramic processing with the milled powder mixtures. The different milling time brought to significant change in power density of the SOFCs. When the powder mixture milled for 5 min was applied, maximum power density of the cell was 0.44 W·cm-2 at 800 °C. Contrarily, 0.75 W·cm-2 was obtained at the same operation temperature when the powder mixture milled for 30min was applied. Structural analysis revealed that the different power density was strongly related to the different anode microstructure. Prolonged milling resulted in homogeneous porous composite layer with fine Ni and YSZ grains, indicating larger triple phase boundary (TPB). It was demonstrated that the appropriate mechanical milling followed by ceramic processing improves the microstructure, and therefore enhances electrochemical activity of the anode.
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Chou, Chen Chia, Chun Feng Huang, and Min Jen Chen. "Fabrication and Characterization of Solid Oxide Fuel Cell Anode with Impregnated Catalytic Ni-CeO2 Nano-Particles on 8YSZ Fibers." Advanced Materials Research 287-290 (July 2011): 2485–88. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2485.
Abstract:
Development of a solid oxide fuel cell anode by impregnating catalytic Ni and Ni-CeO2 nano-particles on 8YSZ fiber structure was carried out in this work. The nano-scale 8YSZ fibers were successfully fabricated by the electrospinning process and were well matched with the 8YSZ electrolyte. The experimental results demonstrated that the Ni/8YSZ anode with nano-8YSZ fibers, which impregnated with 3M nickel nitrate, decreases the polarization resistance and increases the exchange current density. However, the lowest polarization resistance and the highest exchange current density are observed in Ni/8YSZ fibers anode by adding nano-ceria particle from 5 wt.% to 10 wt.%. It is attributed to that the grain growth of Ni particle has been constrained by modifying appropriate amount of ceria particle to reduce the obstruction of diffusion path of fuel gas and to enhance the amount of triple phase boundary (TPB). On the other hand, 8YSZ nano-fibers provide a stabilized porous structure of the anode. Accordingly, nano-CeO2 particle provides storing and releasing of oxygen ion to improve the catalytic performance of nano-Ni modified 8YSZ fiber anode
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Waseem, Saad, Matthew Barre, Katarzyna Sabolsky, Richard Hart, Seunghyuck Hong, and Edward Sabolsky. "Metal Composite Nano-Catalyst Enhanced Solid Oxide Fuel Cell Anodes for Improved Performance and Stability with Hydrocarbon Containing Fuels." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 77. http://dx.doi.org/10.1149/ma2023-015477mtgabs.
Abstract:
Implementation of nano-catalyst materials into solid oxide fuel cell (SOFC) electrodes to improve performance and stability has been widely studied. Addition of the nano-catalysts into an electrode structure serves to enhance the electrochemical performance of the SOFC by increasing the Triple Phase Boundary (TPB) area, improving redox stabilization, and modifying reaction kinetics of hydrocarbon gasses that cause anode degradation due to carbon deposition. SOFCs operating upstream of a reformer need to exhibit good tolerance to any hydrocarbon components that may make their way to the stack. Typical Ni-based cermet anodes suffer from anode deactivation due to carbon build up under hydrocarbon flows. Carbon builds up and covers the TPB area which results in poor electrochemical performance. Larger carbon deposits can block pores within the anode microstructure which leads to gas diffusion issues. Carbon buildup also causes mechanical stresses to the electrode due to volumetric changes which can lead to fracture and complete failure of the cell. This work studied nano-catalyst decoration of the Ni-based cermet anodes with catalysts that promote internal reforming to protect against coking. Addition of active metal components (such as Co, Ge, Sn), and ceramic reforming promoters (such as CeO2, MgO) were investigated. Multi-component systems with several catalysts were also examined. Uniform incorporation of nano-catalyst into the anode microstructure was achieved through a patented liquid phase surfactant assisted process (using various catechol surfactants). Deposition loading densities and distribution of nanoparticles was controlled by altering the surfactant and catalyst solution concentrations. Nano-catalyst depositions were characterized through Scanning Electron Microscope (SEM) for imaging, Atomic Force Microscopy (AFM) for topographical analysis, and Energy-Dispersive X-ray Spectroscopy (EDS) for chemical characterization. Figure 1 shows SEM imaging of nano catalyst distribution of cerium oxide (CeO2) and cobalt oxide (CoO) co-deposition within an anode structure. A uniform distribution of nano-sized catalyst materials is observed. Accelerated evaluation of nano-catalysts for SOFCs was completed through symmetrical anode tests, where a symmetrical anode cell was subjected to hydrocarbon impurity at SOFC operating temperatures and electrochemical impedance spectroscopy (EIS) characterization was done over time. The best catalyst systems were down selected and long-term SOFC tests were completed with current-voltage-power (I-V-P) and EIS evaluation. Post-mortem microstructure and chemistry characterizations were also used in analysis. Uniform nano catalyst distribution of CeO2 and CoO within the anode structure demonstrated greater than 50% sustained improvement in harsh environment, long-term tests where the cell was subjected to 40% CH4 for 50+ h. Figure 1
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Hwang, Jaewon, and Suk Won Cha. "Manipulation of Anode Nanostructure and Composition By Glancing Angle Deposition for Thin-Film Solid Oxide Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 47 (October 9, 2022): 1768. http://dx.doi.org/10.1149/ma2022-02471768mtgabs.
Abstract:
Co-sputtering is a simple yet effective technique for fabricating a thin film of composite materials and different compositions by adjusting the electrical power of each sputtering target. However, practical issues arise when depositing cermet materials such as Ni-YSZ and Ni-GDC because of the contrasting characteristics of metal and ceramic sputtering targets. For example, the surface binding energy of GDC is significantly higher than that of Ni, resulting in a considerably lower sputtering yield of GDC. The difference in sputtering yield is further exacerbated by the low power density limit of the GDC target, which is set by its unfavorable material properties such as brittleness and low thermal conductivity. In contrast, due to its magnetic property, Ni requires sufficiently high sputtering power during magnetron sputtering. This work combines co-sputtering with advanced sputtering techniques such as glancing angle deposition (GLAD) and oblique angle deposition (OAD) to fabricate otherwise unobtainable Ni-GDC anode microstructure with various compositions. Reduced flux capture area of Ni caused by the high incident angle of GLAD allowed control of thin-film compositions, and optimal composition was determined based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. A sufficient amount of GDC was necessary to expand the triple-phase boundary (TPB) and suppress the thermal agglomeration of highly mobile Ni. The effect of electrode nanostructure on fuel cell performance was also investigated. The ballistic shadowing effect during OAD was utilized to produce thin-film electrodes with various porosities. With the increase of the deposition angle, the porosity increased, whereas the in-plane electrical conductivity decreased due to the reduced density. The columnar structure was also manipulated by managing the substrate position through azimuthal rotation. As a result, various columnar structures such as vertical posts, slanted posts, and zig-zag were fabricated, and the optimal microstructure was determined via electrochemical examinations.
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Tanaka, Akihisa, Keisuke Nagato, Morio Tomizawa, Gen Inoue, and Masayuki Nakao. "Modeling of Relative Humidity-Dependent Impedance of Polymer Electrolyte Membrane Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 39 (October 9, 2022): 1366. http://dx.doi.org/10.1149/ma2022-02391366mtgabs.
Abstract:
1. Introduction Polymer electrolyte membrane fuel cells (PEMFCs) are highly efficient devices that utilize hydrogen energy. The large overpotential of PEMFCs, particularly under low relative humidity (R.H.) conditions [1], is a challenge. Equivalent circuit modeling is an effective technique for impedance analysis, in which circuit elements are used to simulate electrode reactions [2]. The transmission line model (TLM) is often used for porous electrodes including PEMFCs [3]. In this study, a TLM was constructed considering the resistance distribution in the cathode catalyst layer (CCL), and the dependence of the impedance on R.H. was investigated. 2. Modeling Figure 1 shows a TLM. The proton potential Xl was set as a parameter for each triple phase boundary (TPB), where an oxygen reduction reaction (ORR) occurs. At a certain TPB, Equation 1 holds based on Kirchhoff's current law [4]. Rion is the proton conduction resistance; Rct is the resistance of charge transfer in the ORR; Tct and P are parameters of the constant phase element. In this study, Rct was made a function of proton potential using Equation 2, where i0 is the exchange current density of the cathode and n is the number of exchanged electrons. The potential X0 of the TPB on a Nafion membrane was specified as the boundary condition. Subsequently, the model impedance was calculated by varying the frequency f from 106 to 0.1 Hz. Using the proposed model, a simulation was performed by varying Rion to be similar to the measured impedance spectra in the next section. For comparison, a simulation was performed under the same conditions using a conventional TLM in which Rct is a constant value. 3. Experimental A membrane electrode assembly (MEA) was prepared by spraying a catalyst ink with an ionomer/carbon weight ratio of 0.92 onto a Nafion membrane. For both the cathode and anode, the electrode area was 1 cm2 and the Pt loading was 0.4 mgpt cm-2. Power generation tests were conducted at a cell temperature of 80 °C. Gases flowing at 200 sccm were supplied to the cathode at an oxygen partial pressure of 0.2 atm and to the anode at a hydrogen partial pressure of 0.4 atm. The impedance spectra of the MEA were measured under various R.H. conditions by electrochemical impedance spectroscopy [5] in the potentiostatic mode at 0.7 V. The distribution of relaxation times (DRT) analysis [6] was conducted on the impedance spectra. 4. Results and discussion Figure 2 shows the experimental and simulation results. The left and right columns show the impedance spectra and the DRT analysis results, respectively. Based on the analysis of DRT peaks by Heinzmann et al. [7], the peak in the mid-frequency range, PM, is associated with the resistance of charge transfer in the ORR, whereas the peak group in the high-frequency range, PH, is associated with the resistance of proton conduction. The PH of the DRT of the measured impedance increases as R.H. decreases. This indicates that a decrease in R.H. promotes a decrease in proton conductivity. The increase in Rion in the simulation represents a decrease in proton conductivity, which increases the PH as shown in both simulation results. As the proton conductivity decreases, the PM of the DRTs of the measured impedance and the calculated impedance using the proposed model increases. However, the PM of the DRT of the calculated impedance using the conventional model does not change. This indicates that the proposed model can accurately simulate the actual phenomena in the CCL. The reason for the increase in PM caused by the decrease in proton conductivity could be that the local charge transfer resistance increases by a decrease in the proton potential at each TPB. 5. Conclusions A TLM was constructed to predict the dependence of impedance on R.H. Experimental results showed that an unsatisfactory proton conductivity resulted in an increase in the charge transfer resistance. The results of the simulation with varying proton conduction resistances using the proposed model are consistent with the experimental trend. In future studies, circuit parameters should be appropriately determined by fitting the model to the measured impedance spectra. References [1] Y. Liu et al., J. Electrochem. Soc. 156, B970–B980 (2009). [2] J. E. B. Randles, Discuss. Faraday Soc. 1, 11–19 (1947). [3] M. Heinzmann et al., J. Power Sources. 444, 227279 (2019). [4] J. H. Teng, Int. J. Electr. Power Energy Syst. 27, 327–333 (2005). [5] X. Yuan et al., Int. J. Hydrogen Energy. 32, 4365–4380 (2007). [6] S. Dierickx et al., Electrochim. Acta. 355, 136764 (2020). [7] M. Heinzmann et al., J. Power Sources. 402, 24–33 (2018). Figure 1
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Sciazko, Anna, Yosuke Komatsu, Takaaki Shimura, Yusuke Sunada, and Naoki Shikazono. "Correlation Between Microstructure and Performance of GDC-Based Electrodes." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 51. http://dx.doi.org/10.1149/ma2023-015451mtgabs.
Abstract:
Gadolinium doped ceria (GDC) gains increasing attention as a promising material for both solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). The GDC-based electrodes demonstrate positive features, e.g. enhanced electrochemical performance in low operation temperatures, resistivity to sulfur poisoning and carbon deposition, etc. As GDC is a mixed electronic-ionic conductor in reducing atmosphere, electrochemical reactions can be supported by the double phase boundary (DPB) at the GDC surface. Several studies demonstrated that the DPB reaction may dominate the electrochemical performance over triple phase boundary (TPB) reaction in Ni-GDC electrodes, where it can account for as much as 95 % of the total reaction depending on the cermet microstructure [1]. Recent studies even show that pure ceria electrodes can achieve substantial power density [2,3]. In this context, the microstructure design principle for GDC-based electrodes should focus on maximizing GDC surface area. Particularly, GDC electrodes with infiltrated GDC nanoparticles or electro-catalytic nanoparticles may achieve competitive performance compared with the conventional Ni-YSZ electrodes. Although many strategies have been proposed to improve performance of GDC-based electrodes, it is difficult to quantitatively compare all the reported results. Furthermore, the correlation between microstructure and performance of pure GDC electrode are still scarce. Several different types of GDC-based electrodes are fabricated and tested in the unified characterization procedure in this study. Four basic designs are considered, i.e. Ni-GDC, GDC-perovskite composites, GDC electrodes with deposited Ni nanoparticles and pure GDC electrodes. Several strategies to modify the GDC surface area are discussed. In addition, the substantial enhancements in the DPB density and electrochemical performance were achieved by precipitating Ni-nanoparticles directly on sub-micron GDC powders at 2wt.% loading. The performance of electrodes was evaluated by electrochemical impedance spectra measurements with various humidity and temperature conditions. The results showed clear dependance between GDC surface area and electrode performance. At the same time, it should be noted that the electrode active thickness depends on the electrode microstructure. In particular, it is in the range of 5 µm for the pure nano-GDC electrode. When the GDC electrode is thicker than the active thickness, it results in large Ohmic resistance due to the electronic conduction in the porous electrode. [1] A. Nenning, M. Holzmann, J. Fleig, A.K. Opitz, Mater. Adv. 2 (2021) 5422–5431. [2] M. Ouyang, A. Bertei, S.J. Cooper, Y. Wu, P. Boldrin, X. Liu, M. Kishimoto, H. Wang, M. Naylor Marlow, J. Chen, X. Chen, Y. Xia, B. Wu, N.P. Brandon, J. Energy Chemistry. 56 (2021) 98–112. [3] W. Jung, K.L. Gu, Y. Choi, S.M. Haile, Energy Env. Sci. 7 (2014) 1685–1692.
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Pidburtnyi, Mykhailo, Haris Masood Ansari, and Viola Ingrid Birss. "Detailed Mechanistic Studies of Electrochemical Reactions on Pt and Au Electrodes in Solid Oxide Cells Via EIS Data Analysis." ECS Meeting Abstracts MA2022-01, no. 49 (July 7, 2022): 2072. http://dx.doi.org/10.1149/ma2022-01492072mtgabs.
Abstract:
In order to reduce the environmental impact of fossil fuels, a range of sustainable technologies for power generation and storage are currently being developed. In addition, efficient and low-cost methods for CO2 capture and conversion to form useful products are critically needed. One of the promising technologies towards achieving these goals involves the use of solid oxide cells (SOC), which are unique devices that can be employed in both the fuel cell mode for clean power generation and in the electrolysis mode to achieve CO2 conversion through its electrochemical reduction (‘CO2RR’). One of the burning problems that is impeding SOC implementation is catalyst selection, with many promising materials having been reported over the last 50 years, including metals and mixed ionic and electronic conducting (MIEC) metal oxide materials. However, the reasons for better or worse activity, as well as the mechanism of the CO2RR at these catalysts remains unknown and it is often unclear what factors limit the catalyst activity during cell operation and how this can be improved. This is due, in part, to the limited number of techniques that can be used to evaluate these performance metrics, especially at high operating temperatures. One of the most useful techniques is electrochemical impedance spectroscopy (EIS). However, data interpretation is often quite complex and thus other methods, such as CNLS fitting or the determination of the distribution of relaxation times (DRT), are needed. While CNLS fitting allows the fit parameters to be correlated with specific physical properties, a precise model of the system is required. Since SOC systems are relatively unexplored and good models are not yet available, this could lead to the mis-interpretation of the EIS data. DRT, on the other hand, can be a useful tool since it does not require any pre-existing models of the system. Unlike CNLS fitting, DRT can provide the correct number of time constants present (from the number of peaks obtained), as well as the associated resistance and capacitance values. According to the literature, each peak is typically related to a specific reaction step with a unique capacitance value, identified by changing conditions such as temperature, polarization or gas composition. In the present work, DRT analysis of Pt and Au electrodes on YSZ electrolytes was carried out in order to determine the origin of each resistance and to determine the effect of temperature, electrode polarization and gas composition on both the resistance and capacitance values. Here, both porous and point metal electrodes were investigated as no double phase boundary activity or chemical capacitance effects should be present, making data interpretation less complex. Furthermore, to avoid the challenges of porous electrodes, point electrodes, produced by pressing the metal wire to a flat YSZ surface by applying pressure with a spring, followed by softening at 1100 °C to achieve better contact, were used to achieve a controllable triple phase boundary (TPB) length. This allowed the true activity of the metal/YSZ TPB to be measured as a function of reactive interface length, rather than just per geometric surface area. Porous electrodes were also studied, made by depositing Pt or Au paste onto YSZ, followed by sintering at 600 °C for 20 min. Polymeric YSZ precursors were then infiltrated into the metallic backbone, then sintered at 750 °C for 2 hours. Then, a thin layer of the same metal paste was applied in order to provide better conductivity. The point electrodes were made by attaching 0.3 mm thick Pt and Au wires onto dense and flat YSZ electrolyte by a spring-loaded cell holder, then held at 1050 °C for 1 hour to soften and produce a fixed TPB length. Electrochemical testing of the porous electrodes was conducted at 750 °C in both half- full cell modes in air, CO2 and CO2/CO mixtures, while the wires were tested at 650-750°C in the same gases, but in half-cell mode. 8 individual process were seen for both the porous and point electrodes, including both electrodes in each cell. The time constant with the smaller capacitors are likely related to the electrode-electrolyte interface, while the mid-range capacitors are associated with electrode surface processes, such as surface diffusion, molecular species dissociation, and adsorption. The high capacitance steps are likely related to gas-phase processes, such as gas diffusion and the possible presence of a conversion layer. More detailed analysis of polarization and gas atmosphere dependence is ongoing in order to confirm the nature of each process.
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Ma, Tien Ching, Manuel Hegelheimer, Andreas Hutzler, Richard Hanke-Rauschenbach, and Simon Thiele. "1D One-Phase Modeling of the Anode Catalyst Layer/Porous Transport Layer Interface Affecting Proton Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2023-02, no. 42 (December 22, 2023): 2132. http://dx.doi.org/10.1149/ma2023-02422132mtgabs.
Abstract:
Optimizing the structure of the porous transport layer (PTL) is crucial for improving the performance of proton exchange membrane water electrolysis (PEMWE), particularly for cells with low anode catalyst loadings. A growing number of studies reveal that catalysts are normally not entirely utilized in PEMWE, whereas the degree of catalyst utilization strongly depends on the structure of the PTL. As the oxygen evolution reaction (OER) at the anode is the limiting reaction step in PEMWE, inefficient use of the anode catalyst layer (aCL) would result in higher activation losses and, thus, cause a waste of unused catalysts [1–3]. This phenomenon becomes more serious when catalyst loading is reduced to meet the eco-friendly requirement of $2 per kgH2 while conserving noble material resources [4]. Schuler et al. [1, 5] combined commercial CCMs with different PTL configurations, and found that with different aCL/PTL interface properties, the activation overpotential could have a maximum deviation of 20 mA at 0.1 A/cm2. Peng et al. [2] manufactured an ultra-low Ir loading CCM with 0.03 mgIr/cm2. Optimizing the aCL/PTL interface showed that the activation overpotential can have a maximum deviation of 40 mV at 0.75 A/cm2. Previous studies concluded that the aCL/PTL interface is crucial for improving the catalyst utilization. Consequently, the triple-phase boundary (TPB) site concept at the aCL/PTL interface is gaining more and more attention: the catalysts can only be entirely activated at reaction sites with sufficient water supply, ionic and electronic conductivities, and oxygen removal pathways [3]. According to TPB, not all reaction sites on the aCL meet these requirements. Figure 1 shows the corresponding physical picture. At the contact point of aCL and PTL (S) offers much greater electronic conductivity compared to the pore area (P), where electron removal is limited by the aCL in-plane conductivity (i.e., 1.85×106 S/m vs. 65.8 S/m) [3]. However, beneath the contact area (S), mass transport of oxygen is limited, indicating the necessity of optimizing the aCL/PTL interface. Figure 1: Illustration of physical picture at aCL/PTL interface. In our contribution, we implement a one-dimensional, one-phase model to investigate the interplay between PTL geometry at the aCL/PTL interface and catalyst utilization. The PTL transports water toward the aCL and electrons and oxygen toward the cathode and anode bipolar plates, respectively [6]. To simplify the physical conditions, we assume sufficient water supply and ion removal for the reaction sites on the aCL. Therefore, mass transport and electron transport limitations are only influenced by the aCL/PTL interface properties. Oxygen is assumed to dissolve in water only so that bubble formation does not disturb the reaction sites. Additionally, an ideal heat management condition is assumed in the model to achieve an isothermal condition. Our simulation results are in good agreement with literature, enabling the prediction of activation overpotentials corresponding to the PTL structure at aCL/PTL interface. Moreover, our results illustrate the local aCL behavior, which can be used to optimize the porous structure at the aCL/PTL interface, maximizing catalyst utilization. With our model, we aim to screen for an optimum PTL structure for a given aCL, allowing us to improve PEMWE cell performance by minimization of activation losses. References [1] T. Schuler, T. J. Schmidt, F. N. Büchi, J. Electrochem. Soc. 166, 10 (2019). [2] X. Peng, P. Satjaritanun, Z. Taie, L. Wiles, A. Keane, C. Capuano, I. V. Zenyuk, N. Danilovic, Adv. Sci. 8, 21 (2021). [3] Z. Kang, J. Mo, G. Yang, Y. Li, D. A. Talley, B. Han, F.-Y. Zhang 255, 20 (2017). [4] D. Kulkarni, A. Huynh, P. Satjaritanun, M. O'Brien, S. Shimpalee, D. Parkinson, P. Shevchenko, F. DeCarlo, N. Danilovic, K. E. Ayers, C. Capuano, I. V. Zenyuk 308, 5 (2022). [5] T. Schuler, R. D. Bruycker, T. J. Schmidt, F. N. Büchi, J. Electrochem. Soc. 166, 4 (2019). [6] M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrog. Energy 38, 12 (2013). Figure 1
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Budac, Daniel, Michal Carda, Martin Paidar, and Karel Bouzek. "Electrical Conductivity of LSM—YSZ Oxygen Electrode for Determining Active Electrode Zone in Solid Oxide Cells." ECS Meeting Abstracts MA2022-01, no. 26 (July 7, 2022): 1233. http://dx.doi.org/10.1149/ma2022-01261233mtgabs.
Abstract:
Solid oxide cells (SOCs) show high potential in applications related to sustainable society. The substantial contribution of the SOCs is their high efficiency in terms of the electric energy utilization due to the operating temperature up to 800 °C. The effect of high operation temperature is favorable in two ways. Firstly, it accelerates the kinetics of electrochemical reactions preventing the need of the use of Pt-based catalysts. Secondly, the high temperature offers favorable thermodynamic conditions decreasing the equilibrium potential for water splitting. This makes the SOCs technology a direct competitor to low-temperature technologies, such as alkaline or PEM electrolysis. The SOCs are composed of electrolyte, fuel electrode and oxygen electrode. The electrolyte allows transport of oxygen ions between the electrodes due to its high ionic conductivity. Yttria-stabilized zirconia (YSZ) represents a typical example of such a material. The oxygen electrode is where the oxygen reduction reaction or the oxygen evolution reaction takes place according to the operation mode of the SOC. Lanthanum strontium manganite (LSM) has been the state-of-the-art oxygen electrode material for almost 25 years and is considered as a pure electron conductor. Lack of ionic conductivity of the LSM leads to limitation of the overall reaction rate to the amount of triple phase boundary (TPB) where gaseous phase, electron-conducting phase and ion-conducting are in simultaneous contact. According to the literature it is optimal for the electrode material to be mixed in the 50:50 ratio with YSZ to increase the amount of the TPB. Thus, the active zone is extended further from the electrolyte surface into the volume of the electrode body. Even though the mixed electrode material exhibits great performance, information on the optimal thickness of the electrode is scarce in the literature. The electrode thickness is a crucial parameter since not all of the electrode volume is electrochemically active and represents just surplus resistance for the electric current impairing the overall electrode performance. The goal of our research is to determine of the extent of the active zone that we can estimate the optimal thickness of the LSM—YSZ electrode for various operation conditions. A macrohomogenous 1D model was developed to simulate the active electrode zone extent. Initial parametric study has shown that the extent of the active region of the electrode is influenced by many factors including the kinetics of the occurring reactions, the ionic and electronic conductivity of the respective domains and working conditions, such as temperature and operating current density. Even though the literature offers data on the conductivity of bulk the LSM and YSZ, the data of the respective conductivities in the LSM—YSZ are not applicable due to the electrode structure. The conductivity of the structure consisting of packed particles with a small contact area is limited by the contact resistance. This study targets to determine the electronic conductivity of the LSM phase and the ionic conductivity of the YSZ phase in the LSM—YSZ electrode framework. The LSM conductivity in the electrode framework was determined by resistance measurement of the casted layers of the LSM—YSZ using electrochemical impedance spectroscopy (EIS). The results show an exponential decrease of the LSM conductivity with decreasing LSM content. Furthermore, the 50:50 LSM—YSZ exhibits conductivity comparable to that of the bulk YSZ electrolyte. This result proves that the energy losses due to the electrical resistance of the LSM—YSZ electrode cannot be neglected in the terms of SOC performance. The determination of the ionic conductivity of YSZ in the electrode framework required the substitution of LSM with an inert material. The material of choice was CaSO4 due to its availability and its melting point being relatively close to that of the LSM. Similarly to the LSM, YSZ exhibited an exponential decrease of ionic conductivity with a decrease in YSZ volume fraction in the samples. Furthermore, the trend was compared to the Koh-Fortini relationship, showing that grain boundaries have a strong influence on the total conductivity of the material. The results of the experiments helped us to determine the extent of the active electrode zone leading to the estimation of optimal thickness of the LSM—YSZ oxygen electrode thickness. The authors acknowledge the financial support of the Czech Science Foundation (GACR), contract No: 19-142-44-J and by the Technology Agency of the Czech Republic under project no. TK04030143.
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Yang, Byung Chan, Sung Eun Jo, Taeyoung Kim, Geonwoo Park, Dohyun GO, Turgut M. Gur, and Jihwan An. "Methanol Fueled Low Temperature Solid Oxide Fuel Cell with Pt-SDC Anodes." ECS Meeting Abstracts MA2022-02, no. 47 (October 9, 2022): 1763. http://dx.doi.org/10.1149/ma2022-02471763mtgabs.
Abstract:
A low-temperature solid oxide fuel cell (LT-SOFC) is a next-generation energy conversion device and has advantages of high energy efficiency, fast start up and shut down and eco-friendliness. In addition, since it has the advantage of being able to use various fuels such as hydrogen, alcohol, and methane gas, research is being actively conducted in recent years. However, LT-SOFC using hydrogen as a fuel has difficulties in storing and transporting fuel, making it difficult to apply as a portable device. On the other hand, methanol fuel is an attractive alternative fuel because it is easier to transport and store than hydrogen fuel and has a high volumetric energy density. However, when methanol is applied to LT-SOFC, there is a disadvantage in performance due to the complicated oxidation process and CO poisoning. Complex methanol oxidation reaction (MOR) and CO poisoning reduce the performance and durability of fuel cells. Therefore, it is important to use a catalyst that can prevent CO poisoning and improve the oxidation reaction of methanol. Pt is an effective catalyst for methanol decomposition and is one of the materials widely used in direct methanol fuel cell (DMFC). However, there is a problem in that it is vulnerable to CO generated during the methanol oxidation process. It is known that CO is adsorbed on the Pt surface, blocks the active site, and reduces catalytic activity. Therefore, alloying Pt with samaria-doped ceria (SDC) with high oxygen storage capacity (OSC) and good OH generation capacity can be effective to reduce CO poisoning and coking. In this study, we prepared the cells with Pt-SDC cermet anodes with the Pt volume percent of 69 (Pt 0.69), 83 (Pt 0.83), 92 (Pt 0.92), and 95 (Pt 0.95) volume% by varying Pt and SDC powers in the co-sputtering process. In the electrochemical impedance spectroscopy (EIS), ohmic resistance was similar between all samples; on the other hand, activation resistance was measured to be 24.0, 19.5, 31.8, 30.8, and 53.0 Ω∙cm2 at Pt 0.69, Pt 0.83, Pt 0.92, Pt 0.95, and Pt 1 samples, respectively, confirming the lowest activation resistance at Pt 0.83. We speculate that the MOR is improved by the increase of triple phase boundary (TPB) sites and the facilitation of bifunctional CO oxidation mechanisms with higher content of SDC up to 17 mol% (Pt 0.83). However, in the anode with excessive SDC content (31 mol%, Pt 0.69), the Pt is oxidized to form PtO2, lowering the catalytic activity.
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Kamiya, Kazuhide. "(Invited) High-Rate CO2 Reduction Reactions: From Electrocatalysts to Gas-Diffusion Electrodes." ECS Meeting Abstracts MA2023-02, no. 47 (December 22, 2023): 2366. http://dx.doi.org/10.1149/ma2023-02472366mtgabs.
Abstract:
Excessive emissions of carbon dioxide (CO2) from the use of fossil fuels are becoming a serious obstacle to the sustainable development of society. Electrochemical CO2 reduction (CO2RR) into value-added products using solar electricity is a promising technology to close the carbon cycle and sequester anthropogenic CO2 into chemical feedstocks.[1] The practical implementation of CO2RR requires a high current density, as the current density for CO2RR is directly correlated to the capital cost of the electrodes and electrochemical cells. The use of gas diffusion electrodes (GDEs) effectively accelerates CO2RR by overcoming the mass transport limitation due to the inherently low diffusion and solubility of CO2 in water. This presentation summarises our recent studies on high-rate CO2RR from the point of view of both novel electrocatalyst designs and appropriate electrode assembly. Single-atom electrocatalysts (SAECs), consisting of single isolated metal sites dispersed on heterogeneous supports, are one of the promising electrocatalysts for high-rate gaseous CO2RR. We have employed various single metal-doped covalent triazine frameworks (M-CTFs) as a platform for CO2RR electrocatalysts on GDEs and systematically investigated them to derive sophisticated design principles using a combined computational and experimental approach.[2-4] The Ni-CTF exhibited both high selectivity and high reaction rate for CO production. In contrast, the Sn-CTF exhibited selective formic acid production, and the faradaic efficiencies (FEs) and partial current density reached 85% and 150 mA/cm2, respectively.[2] These results were in close agreement with the intermediate CO2RR adsorption strength obtained by DFT calculations. In addition to the synthesis of efficient electrocatalysts, the triple phase boundary (TPB) at the GDE, where the catalyst material, electrolyte, and gas pores intersect, needs to be enlarged for high-rate gaseous CO2RR.[5,6] We successfully increased the partial current density for multicarbon products (C2+) over cupric oxide (CuO) nanoparticles on gas diffusion electrodes in neutral electrolytes to a record value of 1.7 A/cm2 by maximizing the area of the CO2RR active interface.[5] In particular, we demonstrated that the thickness of catalyst layers was one highly sensitive factor in determining the maximum current density for C2+. Although the GDE and electrocatalyst used in this case are not unique, the optimized assembly elicits their undermined potential. [1] K. Kamiya, Nakanishi* et al. Chem. Lett. 2021, 50, 166-179. [2] S. Kato, K. Kamiya* et al. Chem. Sci., 2023, 14, 613–620. [3] P. Su, K. Kamiya*et al. , Chem. Sci., 2018, 9, 3941-3947. [4] K. Kamiya* Chem. Sci. 2020, 11, 8339–8349. [5] A. Inoue, K. Kamiya* et al. EES Catal. 2023, 1, 9-16. [6] T. Liu*, K. Kamiya* et al. Small 2022, 18, 2205323.
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Zhu, Mei, and Xian Zhi Xu. "The Three-Phase Boundary Dynamic Variation of the Porous Gas Electrode." Advanced Materials Research 255-260 (May 2011): 1810–14. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1810.
Abstract:
In order to observe the three-phase boundary (TPB) variation of the porous gas electrode, a new laying style of the porous gas electrode was proposed. Two electrodes with different ingredient were taken in the experiment under the same condition to testify that there are three distinct stages of the TPB dynamic variation.Each stage has its own apparent phenomenon and the variation time of each stage is different for each electrode. The relationship between the electric conductance and the TPB variation of the electrode were also analyzed by the theoretical calculating formula. The result showed that the internal resistance increases as the decrease of the electric conductance created by the TPB variation. The research above illustrated this laying style of the porous gas electrode can be effectively used to observe the TPB dynamic variation.
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O’Hayre, Ryan, David M. Barnett, and Fritz B. Prinz. "The Triple Phase Boundary." Journal of The Electrochemical Society 152, no. 2 (2005): A439. http://dx.doi.org/10.1149/1.1851054.
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Khandale, Anushree P., and R. Vinoth Kumar. "Facile and Low Temperature Synthesis of Nd1.8Sr0.2NiO4-δ Cathode Nanofibers for Intermediate Temperature Solid Oxide Fuel Cells." ECS Meeting Abstracts MA2023-02, no. 46 (December 22, 2023): 2271. http://dx.doi.org/10.1149/ma2023-02462271mtgabs.
Abstract:
Solid oxide fuel cells (SOFCs) are usually operated at high temperatures (800-1000 °C). As the overall efficiency of SOFC is governed by thermodynamics and kinetics during operation, reducing the operating temperature to 500-650 °C causes significant increase in the electrode polarization losses especially at cathode due to high activation energy towards oxygen reduction reaction (ORR) at cathode, which eventually reduces the overall cell performance. Addressing increased polarization losses at relatively low temperatures (500-650 °C) has been the key issue and a focus of many groups over past couple of decades. Conventional cathode materials lose their ORR activity and so discarded for intermediate temperature (IT)-SOFC application. In this regard, mixed ionic-electronic conductors (MIECs) offer high thermal and chemical stability along with high oxygen diffusion and good electronic conductivity at IT [1,2]. In addition, Ruddlesden-Popper (RP) type MIECs with A2BO4 structure have been demonstrated as promising cathode for IT- SOFCs due to their unique structure, rapid oxygen surface exchange kinetics, and excellent stability in atmosphere. Particularly Nd2NiO4+δ oxides offer an excellent oxygen diffusion coupled with high surface exchange coefficients and comparable thermal expansion coefficients with those of oxygen-ion conductors (YSZ and CGO) [2]. Enhanced electronic conductivity and electrochemical performance have been demonstrated for partial replacement of Nd with Sr in our previous reports [3]. Albeit, the intrinsic material properties such as electrochemical catalytic activity and electrical conductivity are of primary importance, an actual electrode performance strongly depends on its microstructure. Therefore, in addition to using high catalytic and conductive materials, achieving an extremely high-power density, thus, requires a finely controlled electrode microstructure, to expand the electrochemically active triple-phase boundary (TPB). Recently, electrospinning has been considered as an efficient, cost effective and promising method for synthesis of ceramic nanofibers. Pertinent literature suggests that SOFC with cathode nanofiber has superior/better performance (nearly doubled power density and significant reduced polarization resistance) compared to powder type electrodes. Selection of suitable cathode materials with modified microstructure (nanofibers) would facilitate more electrochemically active sites for the oxygen reduction at relatively low temperatures <650 °C. In this paper we synthesized Nd1.8Sr0.2NiO4-δ (NSNO) cathode nanofibers using electrospinning technique and compared its electrochemical performance with NSNO nanopowder. Practically, 10 wt.% Polyvinylpyrrolidone (PVP) solution was prepared by dissolving it in ethanol, to which stoichiometric amounts of Nd-nitrate, Sr-nitrate, Ni-nitrate (total weight percentage of metal salts- 3 wt%) were added, together with some deionized water. The mixture was then stirred for 10 h at room temperature on a magnetic stirrer to obtain a homogeneous sol. The sol was loaded into the electrospinning syringe. Distance between the spinneret and the collector was fixed at 25 cm and the high-voltage supply was maintained at 30 kV. The spinning rate was controlled at 5 ml h- 1 by a syringe pump. The obtained nanofibers were dried at 80 °C for 12 h, then sintered at 900 °C for 2 h in air to obtain single-phase NSNO. The obtained nanofibers were characterized using room temperature XRD, XPS, SEM and dc electrical conductivity (400-650 °C). In addition, electrochemical impedance spectroscopy studies on symmetric cells were carried out as a function of temperature (400-650 °C). Improved electrochemical performance is attributed to enhanced electrochemical active sites for ORR due to nanofibers and optimum porosity. References [1] S.J. Skinner, J.A. Kilner, Solid State Ionics. 135 (2000) 709. [2] E. Boehm, J.M. Bassat, P. Dordor, F. Mauvy, J.C. Grenier, P. Stevens, Solid State Ionics. 176 (2005) 2717. [3] A.P. Khandale, J.D. Punde, S.S. Bhoga, J. Solid State Electrochem. 17 (2013) 617.
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Yamagishi, Rena, Anna Sciazko, Yosuke Komatsu, and Naoki Shikazono. "(Digital Presentation) Synthesizing Electrode Microstructures with Predefined Spatial Gradients By Conditional Generative Adversarial Networks." ECS Meeting Abstracts MA2022-01, no. 38 (July 7, 2022): 1683. http://dx.doi.org/10.1149/ma2022-01381683mtgabs.
Abstract:
Recent progress of manufacturing techniques in the field of solid oxide fuel cells (SOFCs) enables fabrications of complex multi-sized gradient microstructures with the spatially varied properties. Methods using additive manufacturing, layer-by-layer deposition, tape casting, nano-imprint, pulse laser deposition and laser engraving, etc. provide possibilities to fabricate 3D structures with flexible design. Moreover, the spatially optimized structures can provide better mechanical and thermal properties, enhance diffusion and improve electrochemical reaction kinetics. In particular, multi-layered electrode designs are attracting increasing interest. The layered electrode design and optimization require effective methods to fabricate synthetic microstructures with property gradients. The generative adversarial network (GAN) proves its usabilities in fabricating artificial microstructures belonging to the same class as the training data [1] and reconstructing 3D structures from 2D image [2], etc. The applications primarily focus on the structures with uniform spatial properties identical to the training sample. The Wasserstein GAN was recently applied for the fast inverse design of two-phase homogenous microstructures with user-defined properties [3]. In this study, an approach using conditional GAN (C-GAN) is proposed to flexibly generate multi-phase structures with predefined gradients. The proposed method is tested on the microstructures of porous nickel-gadolinium doped ceria (Ni-GDC) SOFC anodes. The C-GAN training dataset consists of real Ni-GDC microstructures with varied Ni and GDC compositions (GDC share in the range of 30 – 70 vol%) and with varied porosity [4]. In total, 10 different samples were prepared and sintered at 1350 oC in air atmosphere and further reduced in the H2 flow at 800 oC. The fabricated electrodes had significantly different microstructural properties and electrochemical performance. The samples were infiltrated with epoxy resin to enable clear phase recognition, polished to expose cross-section and characterized by the scanning electron microscope (SEM). The SEM images were segmented prior to the C-GAN training. The C-GAN was trained with patches of 256 x 256 pixels which were randomly extracted from SEM images of each sample. The sample with Ni : GDC = 50 : 50 vol% was excluded from the training data and used only for testing. The generator network input consists of 4 variables: random noise vector, Ni share in composite, porosity and particle size (Fig. 1A). The particle size is controlled by the magnification of the training images. The Ni volume fraction and porosity are calculated separately for each patch during the iterative training process. The primary version of the trained C-GAN network generates homogenous artificial microstructures with the patch size of 256 x 256 pixels identical to the training data. The fabricated microstructures (Fig. 1B) show excellent visual and good statistical agreements with the real samples. It is possible to reproduce not only the volumetric fractions, but also the surface area density and triple phase boundary density of the real Ni-GDC electrodes (Fig. 1C). The C-GAN can fabricate not only the microstructures belonging to the training dataset, but also samples with other compositions. Although the C-GAN generator was trained based on patches with 256 × 256 pixels, it can be used for the fabrication of larger structures by increasing the size of the generator input. By adjusting the generator input matrix consisting of the Ni share, porosity and particle size, various microstructure patterns can be fabricated including linear gradients (Fig. 1D) and layered structures (Fig. 1E). Those structures have a significance for the SOFC anodes design as layered designs are conventionally incorporated in SOFC electrodes, e.g. support and active anode layers. In addition, it was shown that the graded structures have superior performance compared with the isotropic anodes [5]. The proposed framework provides a convenient tool for generating realistic microstructures with wide range of predefined properties. Further, it can be coupled with the existing simulation tools to evaluate the wide range of graded and layered microstructural designs. [1] A. Gayon-Lombardo, L. Mosser, N. P. Brandon, and S. J. Cooper, npj Comput. Mater., 6, 1–11 (2020). [2] A. Sciazko, Y. Komatsu, and N. Shikazono, ECS Trans., 103, 1363–1373 (2021). [3] X. Lee, et al., Nature Computational Science, 1, 229, (2021). [4] Y. Komatsu, A. Sciazko, and N. Shikazono, J. Power Sources, 485, 229317 (2021). [5] Z. Yan, et al., ECS Trans., 91, 2055, (2019). Fig. 1. A) Schema of C-GAN network, B) synthetic homogenous microstructures fabricated by C-GAN, C) TPB dependence on the Ni and pore volume fractions, D) synthetic structure with predefined gradient and E) synthetic layered structure. Figure 1
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Dhanda, Abhishek, Ryan O'Hayre, and Heinz Pitsch. "EIS Analysis of the Triple Phase Boundary Model." ECS Transactions 19, no. 32 (December 18, 2019): 23–31. http://dx.doi.org/10.1149/1.3268159.
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Lorenz, Oliver, Alexander Kühne, Martin Rudolph, Wahyu Diyatmika, Andrea Prager, Jürgen W. Gerlach, Jan Griebel, et al. "Role of Reaction Intermediate Diffusion on the Performance of Platinum Electrodes in Solid Acid Fuel Cells." Catalysts 11, no. 9 (August 31, 2021): 1065. http://dx.doi.org/10.3390/catal11091065.
Abstract:
Understanding the reaction pathways for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) is the key to design electrodes for solid acid fuel cells (SAFCs). In general, electrochemical reactions of a fuel cell are considered to occur at the triple-phase boundary where an electrocatalyst, electrolyte and gas phase are in contact. In this concept, diffusion processes of reaction intermediates from the catalyst to the electrolyte remain unconsidered. Here, we unravel the reaction pathways for open-structured Pt electrodes with various electrode thicknesses from 15 to 240 nm. These electrodes are characterized by a triple-phase boundary length and a thickness-depending double-phase boundary area. We reveal that the double-phase boundary is the active catalytic interface for the HOR. For Pt layers ≤ 60 nm, the HOR rate is rate-limited by the processes at the gas/catalyst and/or the catalyst/electrolyte interface while the hydrogen surface diffusion step is fast. For thicker layers (>60 nm), the diffusion of reaction intermediates on the surface of Pt becomes the limiting process. For the ORR, the predominant reaction pathway is via the triple-phase boundary. The double-phase boundary contributes additionally with a diffusion length of a few nanometers. Based on our results, we propose that the molecular reaction mechanism at the electrode interfaces based upon the triple-phase boundary concept may need to be extended to an effective area near the triple-phase boundary length to include all catalytically relevant diffusion processes of the reaction intermediates.
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Dhanda, Abhishek, Heinz Pitsch, and Ryan O’Hayre. "Diffusion Impedance Element Model for the Triple Phase Boundary." Journal of The Electrochemical Society 158, no. 8 (2011): B877. http://dx.doi.org/10.1149/1.3596020.
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Beitner, Tzvia, Sioma Baltianski, Ilan Riess, and Yoed Tsur. "Novel method for determining the triple phase boundary width." Solid State Ionics 288 (May 2016): 322–24. http://dx.doi.org/10.1016/j.ssi.2015.11.026.
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Park, Bum Jun, and Daeyeon Lee. "Spontaneous Particle Transport through a Triple-Fluid Phase Boundary." Langmuir 29, no. 31 (July 26, 2013): 9662–67. http://dx.doi.org/10.1021/la401183u.
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GARCKE, HARALD, and BRITTA NESTLER. "A MATHEMATICAL MODEL FOR GRAIN GROWTH IN THIN METALLIC FILMS." Mathematical Models and Methods in Applied Sciences 10, no. 06 (August 2000): 895–921. http://dx.doi.org/10.1142/s021820250000046x.
Abstract:
We use geometrical arguments based on grain boundary symmetries to introduce crystalline interfacial energies for interfaces in polycrystalline thin films with a cubic lattice. These crystalline energies are incorporated into a multi-phase field model. Our aim is to apply the multi-phase field method to describe the evolution of faceted grain boundary triple junctions in epitaxially growing microstructures. In particular, we are interested in symmetry properties of triple junctions in tricrystalline thin films. Symmetries of triple junctions in tricrystalline films have been studied in experiments by Dahmen and Thangaraj.6,25 In accordance with their experiments, we find in numerical simulations that any two neighboring triple junctions belong to different symmetry classes. We introduce a local equilibrium condition at triple junctions which can be interpreted as a crystalline version of Young's law. The local equilibrium condition at triple junctions is purely determined by the grain boundary energies. In particular no triple junction energies are necessary to explain which triple junctions are possible. All triple junctions observed in the experiments as well as in the simulations fulfil the crystalline version of Young's law. Our approach is also capable of describing grain boundary motion in general polycrystalline thin films.
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Vijay, Periasamy, Moses O. Tadé, Zongping Shao, and Meng Ni. "Modelling the triple phase boundary length in infiltrated SOFC electrodes." International Journal of Hydrogen Energy 42, no. 48 (November 2017): 28836–51. http://dx.doi.org/10.1016/j.ijhydene.2017.10.004.
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Vagin, Mikhail Yu, Arkady A. Karyakin, Anne Vuorema, Mika Sillanpää, Helen Meadows, F. Javier Del Campo, Montserrat Cortina-Puig, Philip C. Bulman Page, Yohan Chan, and Frank Marken. "Coupled triple phase boundary processes: Liquid–liquid generator–collector electrodes." Electrochemistry Communications 12, no. 3 (March 2010): 455–58. http://dx.doi.org/10.1016/j.elecom.2010.01.018.
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Moon, Yong Hyun, Na Yun Kim, Sung Min Kim, and Youn Jeong Jang. "Recent Advances in Electrochemical Nitrogen Reduction Reaction to Ammonia from the Catalyst to the System." Catalysts 12, no. 9 (September 7, 2022): 1015. http://dx.doi.org/10.3390/catal12091015.
Abstract:
As energy-related issues increase significantly, interest in ammonia (NH3) and its potential as a new eco-friendly fuel is increasing substantially. Accordingly, many studies have been conducted on electrochemical nitrogen reduction reaction (ENRR), which can produce ammonia in an environmentally friendly manner using nitrogen molecule (N2) and water (H2O) in mild conditions. However, research is still at a standstill, showing low performances in faradaic efficiency (FE) and NH3 production rate due to the competitive reaction and insufficient three-phase boundary (TPB) of N2(g)-catalyst(s)-H2O(l). Therefore, this review comprehensively describes the main challenges related to the ENRR and examines the strategies of catalyst design and TPB engineering that affect performances. Finally, a direction to further develop ENRR through perspective is provided.
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Li, Kai, Yao Shen, Da Yong Li, and Ying Hong Peng. "Phase Field Study of Second Phase Particles-Pinning on Strain Induced Grain Boundary Migration." Materials Science Forum 993 (May 2020): 967–75. http://dx.doi.org/10.4028/www.scientific.net/msf.993.967.
Abstract:
A phase field model was presented to investigate the effect of particles-pinning on grain boundary migration in materials containing stored energy differences across the grain boundaries. The accuracy of the phase field framework was examined by comparing the simulated results with theoretical predictions. The pinning effects of coherent and non-coherent second phase particles on the boundary migration were studied in triple-grain models. 2D simulations with second phase particles of different sizes or different area fractions were performed. The effect of stored energy difference across the boundary on the particles-pinning was also investigated. The results showed that the pinning effect could be enhanced by the decrement of the particle size and the increment of particle area fraction. Increasing the stored energy difference across the grain boundary induced higher grain boundary migration velocity and weaker particles-pinning.
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Iskandarov, Albert M., and Tomofumi Tada. "Dopant driven tuning of the hydrogen oxidation mechanism at the pore/nickel/zirconia triple phase boundary." Physical Chemistry Chemical Physics 20, no. 18 (2018): 12574–88. http://dx.doi.org/10.1039/c7cp08572a.
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Lee, Joon-Hyung, Jeong-Joo Kim, Haifeng Wang, and Sang-Hee Cho. "Observation of Intergranular Films in BaB2O4-added BaTiO3 Ceramics." Journal of Materials Research 15, no. 7 (July 2000): 1600–1604. http://dx.doi.org/10.1557/jmr.2000.0229.
Abstract:
Distribution characteristics of boundary phase in BaB2O4 added BaTiO3 ceramics were investigated with a focus on the curvature difference of solid–liquid interfaces at two-grain and triple junctions. High-resolution transmission electron microscopy revealed that the triple junction of solid grains showed the positive curvature of solid–liquid interface and consisted of the mixture of liquid phase and crystallized BaB2O4 phase. On the other hand, flat amorphous thin film of 2.5-nm thickness was observed at the two-grain junction. This kind of boundary phase distribution characteristic was explained by the solubility difference between two kinds of junctions of solid grains that had different curvature of solid–liquid interfaces.
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Basak, Anup. "Grain boundary-induced premelting and solid ↔ melt phase transformations: effect of interfacial widths and energies and triple junctions at the nanoscale." Physical Chemistry Chemical Physics 23, no. 33 (2021): 17953–72. http://dx.doi.org/10.1039/d1cp02085d.
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Gamalski, A. D., C. Ducati, and S. Hofmann. "Cyclic Supersaturation and Triple Phase Boundary Dynamics in Germanium Nanowire Growth." Journal of Physical Chemistry C 115, no. 11 (March 3, 2011): 4413–17. http://dx.doi.org/10.1021/jp1095882.