Academic literature on the topic 'PGM-free catalysts'

Platinum group metal (PGM) catalysts are the major electrocatalysts for oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cells (PEMFCs). However, the high cost of PGM catalysts is the major huddler for the widespread applications of fuel cell electric vehicles. To remove this cost obstacle of fuel cell commercialization, PGM-free catalysts have been considered as the replacement of PGM catalysts for ORR because of the low cost and relatively comparable performance with PGM catalyst. Fe-C-N complex is the one of the most active centers in PGM-Free catalyst groups. This type of catalyst shows excellent activity characterized using the rotation disk electrode (RDE), i.e., the half wave potential (E1/2 ) could reach 0.91 V versus standard hydrogen electrode (SHE). However, in a membrane electrode assembly (MEA), the performance of PGM-Free catalysts cannot achieve the comparable performance to PGM catalyst. Since there are so many differences between PGM-free, and PGM catalysts e.g., activity, stability, surface conditions, particle size etc. The fabrication of PGM-Free catalyst MEA cannot simply borrow the methods from that of making PGM MEA. In addition, the thicknesses of catalyst layers of PFM-free are significantly thicker than that of PGM, i.e., 10 times. Hereby, we proposed a novel method of fabricating PGM-Free catalyst MEA, so that the intrinsic catalyst activity from RDE can be translated into MEA performance. The method is based on the catalyst coated membrane (CCM) method using optimized ionomer to carbon (I/C) ratio and solvent mixture of catalyst ink. Such method pushes PGM-free MEA first ever achieved the current density of 50.8 mA cm-2 at 0.9 V iR-free in H2/O2 and over 150 mA cm-2 at 0.8 V in H2/air, which surpassed the 2025 performance targets of US Department of Energy (DOE) for PGM-Free catalyst MEA. Further, the property (solvent composition, dispersion of catalyst and ionomer in an ink), structure (pore structure) and the MEA performance have been characterized using mercury intrusion porosimetry (MIP), MEA testing. A property-structure-performance relationship has been established.

The development of active hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts for use in anion exchange membrane fuel cells (AEMFCs), which are free from platinum group metals (PGMs), is expected to bring this technology one step closer to commercial applications. This paper reports our recent progress developing HOR Pt-free and PGM-free catalysts (Pd/CeO2 and NiCo/C, respectively), and ORR PGM-free Co3O4 for AEMFCs. The catalysts were prepared by different synthesis techniques and characterized by both physical-chemical and electrochemical methods. A hydrothermally synthesized Co3O4 + C composite ORR catalyst used in combination with Pt/C as HOR catalyst shows good H2/O2 AEMFC performance (peak power density of ~388 mW cm−2), while the same catalyst coupled with our flame spray pyrolysis synthesised Pd/CeO2 anode catalysts reaches peak power densities of ~309 mW cm−2. Changing the anode to nanostructured NiCo/C catalyst, the performance is significantly reduced. This study confirms previous conclusions, that is indeed possible to develop high performing AEMFCs free from Pt; however, the challenge to achieve completely PGM-free AEMFCs still remains.

Platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) have attracted significant attention in the last two decades. These catalysts typically perform better in alkaline aqueous electrolytes than in their acidic counterparts.1, 2 However, the performance of PGM-free ORR catalysts in anion exchange membrane fuels cells (AEMFCs) have been consistently lower than in the acidic polymer electrolyte fuel cells (PEFCs). The most likely reasons for the sub-par behavior of PGM-free catalysts in AEMFCs has been often linked to difficulties in preparing electrodes with anion exchange ionomers and assuring efficient water management. These challenges have been amplified by the high-loading requirement for PGM-free ORR catalysts, resulting in electrodes by as much as an order of magnitude thicker than the PGM-based ones. In this presentation, we will demonstrate AEMFCs with much improved performance of the PGM-free cathode (Fe-N-C catalyst-based). The performance improvement has been achieved by optimizing the electrode fabrication process, including changes to the electrode configuration and catalyst ink preparation. These changes have allowed us to elevate the AEMFC performance, including the peak power density of > 0.8 W cm-2 in H2-O2 cells, to the level comparable to that of the corresponding PEFC, operating with a PGM-free cathode under the same operating conditions. References: 1. Li, X.; Liu, G.; Popov, B. N., Activity and stability of non-precious metal catalysts for oxygen reduction in acid and alkaline electrolytes. Journal of Power Sources 2010, 195 (19), 6373-6378. 2. Choi, C. H.; Lim, H.-K.; Chung, M. W.; Chon, G.; Ranjbar Sahraie, N.; Altin, A.; Sougrati, M.-T.; Stievano, L.; Oh, H. S.; Park, E. S.; Luo, F.; Strasser, P.; Dražić, G.; Mayrhofer, K. J. J.; Kim, H.; Jaouen, F., The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium. Energy & Environmental Science 2018, 11 (11), 3176-3182.

Platinum-group-metal-free (PGM-free) catalysts are currently considered as potential oxygen-reduction-reaction (ORR) catalysts to replace costly and supply-limited platinum at the cathode side of proton exchange membrane fuel cells (PEMFCs). Extensive research efforts have led to substantial progress with regards to the ORR activity of PGM-free ORR catalysts, but there is uncertainty about the dependence of the mass activity on the catalyst loading. In this study, the effect of catalyst loading on the mass activity is investigated by means of rotating disk electrode measurements as well as single cell PEMFC tests using a commercial PGM-free ORR catalyst. Single cell tests with a wide range of loadings (0.4–4.0 mgcat cm−2 MEA) are compared to rotating disk electrode measurements with low loadings of 40–600 μgcat cm−2 disk. In contrast to indications in the literature that the ORR activity depends on catalyst loading, our results reveal an independence of the ORR mass activity from the catalysts loading in both RDE and PEMFC tests, if corrections for the voltage losses in H2/O2 single cell tests are considered. Moreover, no clear relation of the stability to the catalyst loading was found in H2/O2 PEMFCs.

Ternary NiFeTiOOH Catalyst for the Oxygen Evolution Reaction: Study of the Effect of the Addition of Ti at Different Loadings Wenjamin Moschkowitsch and Lior Elbaz Chemistry Department, Bar-Ilan University, Ramat-Gan 5290002, Israel The demand for energy is expected to grow rapidly in the next decades, but it cannot be solely fulfilled with fossil fuel-based technologies without having a huge impact on the environment. The shift to production of clean energy from alternative sources, such as wind and sun, raise the importance of energy storage technologies. One of the most prominent solutions is storing surplus energy, harvested at peak production times and seasons, in hydrogen. However, the production of hydrogen with methods that require as little energy as possible, as well as being sustainable, environmentally friendly and cheap, are still considered to be a big challenge. Water electrolysis is the simplest industrial process for hydrogen production, and can be linked to fuel cells technology. Among the available electrolyzers, alkaline electrolyzers (ALE) are considered state-of-the-art. Although they can work with platinum-group metal-free (PGM-free) catalysts, unfortunately, this technology still requires the use of PGM catalysts in order to increase the current density, and lower the reaction activation energy. In electrolyzers, water splits into oxygen and hydrogen in two separate reactions, taking place at the anode and cathode. The cathodic reaction is the Hydrogen Evolution Reaction (HER), which is considered to be relatively facile. The anodic, Oxygen Evolution Reaction (OER), is considered to be much more difficult, since it is a four-electron process with very sluggish kinetics. The best known catalysts for this reaction in acidic medium are IrO2 and RuO2, oxides of very rare and precious metals (Ir is the scarcest metal on earth’s crust). In addition, in acidic medium, most PGM-free catalysts, based on earth abundant elements, are considered unstable (these conditions have also shown to be detrimental for Ir and Ru-based catalysts). In contrast, in ALEs, PGM-free catalysts have shown to be a good alternative to PGM catalysts. The most common OER PGM-free catalysts are first-row transition metals in their oxide, hydroxide and oxyhydroxide forms.One such catalyst is nickel oxyhydroxide (NiOOH). The structure of this specific catalyst has been studied in great detail by many different research groups, yet there are several open questions regarding the OER mechanism, i.e. the exact catalytic center and active phase.Recent studies suggest that pure NiOOH is not very active at all, and that all of the activity can be attributed to iron impurities.Indeed, NiFeOOH with iron content of 15-25 %at, has a much higher activity and a much lower overpotential compared to other PGM-free catalysts. It can thus be regarded as a benchmark for this class of OER catalysts.It is well accepted by now that the bimetallic catalyst further increases the intrinsic catalytic activity, and that addition of other transition metals,can further increase it.

The rising interest in polymer electrolyte fuel cell (PEFC) technology, part of the global shift in energy production to clean sources, is accompanied by efforts to drive down the cost of this technology, which focus primarily on the cathode catalyst, the most expensive PEFC component. While platinum-group metals (PGMs) continues to be the materials of choice for oxygen reduction reaction (ORR) catalysts, use of these materials in PEFCs must be significantly reduced or eliminated without a penalty in the overall cell performance for PEFC technology to become fully viable. The most promising class ORR catalysts that do not utilize PGMs (i.e., PGM-free catalysts), involve first-row transition metals, such as iron and cobalt incorporated in a nitrogen-doped carbon (M-N-C catalysts). While advancements in M-N-C activity have been impressive, the much sought-after improvement in durability has been impeded by limited information on changes in the PGM-free catalyst active site density, activity and its degradation rate during fuel cell testing. Currently, degradation of PGM-free catalysts during fuel cell operation is often quantified using the low-current region of polarization curves. While this approach is well established, it neglects complications from such factors as catalyst pore structure, membrane conductivity, ionomer content, nature of the support, and the inhomogeneity of active sites. Hence, there exists a critical need for a method with high specificity towards catalytic activity. In this presentation we will report for the first time on the use of Fourier-transform alternating current voltammetry (FTacV) as an electrochemical method for accurately quantifying the electrochemically active site density of PGM-free ORR catalysts and following their degradation in situ during operation of polymer electrolyte fuel cells. Using this method, we were able to detect changes in performance of electrochemically active species (electrocatalytic centers in this case), allowing us to calculate the electrochemical active site density (EASD) for the first time, which is necessary to elucidate the degradation mechanisms of PGM-free ORR catalysts that occur in situ fuel cells. large-amplitude FTacV, a well-established electrochemical method with distinct advantages over dc methods, was utilized to quantify the electrochemically active site density of PGM-free FeNC catalysts in situ in PEFC. First, we will demonstrate that an accurate measurement of the EASD can be made using this method. To further emphasize the strength of the technique, we will present our findings during degradation of commercial FeNC catalysts in operating PEFC. The peak currents from higher harmonics produced by this method are correlated to the fuel cell performance, and decrease after durability tests in a manner that indicates EASD loss may not be the only catalyst degradation mechanism, thus inviting further studies of yet-unknown degradation pathway(s).

Platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) with atomically dispersed FeN₄ sites have emerged as a potential replacement for low-PGM catalysts in acidic polymer electrolyte fuel cells (PEFCs).

The increasing availability of renewable energy sources, especially solar power, coupled with the desire to reduce greenhouse gas emissions, has led to an increased interest in using renewables to satisfy global energy demand. Hydrogen is an attractive alternative to fossil fuels due to its potential for emissions reductions and advantages in storage and transportation. Direct solar-to-hydrogen generation would enable the conversion of renewable energy and water into a storable fuel, thereby drastically reducing carbon emissions. However, current hydrogen production from commercial PEM electrolysis systems requires acidic environment which necessitates the use of expensive platinum group metal (PGM) catalysts and corrosion resistant cell stack components. Thus, a stable, robust, and inexpensive anion exchange membrane and PGM-free catalysts are needed to make alkaline solar water splitting commercially viable as a replacement for the expensive PEM system. We have developed a fully PGM-free electrolyzer using anion exchange membrane (AEM) in an alkaline environment that operates at 80 °C. Using carbon supported NiMo as hydrogen evolution reaction (HER) catalyst and NiFe as oxygen evolution reaction (OER) catalyst, in combination with commercially available AEM from Versogen, we were able to achieve a stable performance of 1.504 V at 100 mA/cm2, compared with baseline PGM cell at 1.508 V, in alkaline environment. At 2 A/cm2, the fully PGM-free cell demonstrated 200 mV higher potential compared to the PGM baseline cell at 2.009 V. Furthermore, we were able to run more than 200-hour at constant current density 2 A/cm2, with 85 mV performance loss. Further developments in catalyst performance and membrane stability, as well as integration with photovoltaics to enable hydrogen production from water, are underway. Acknowledgement: The project is financially supported by the Department of Energy’s Office of Science under the Grant DE-SC0020576

AbstractProton exchange membrane (PEM) fuel cells have gained increasing interest from academia and industry, due to its remarkable advantages including high efficiency, high energy density, high power density, and fast refueling, also because of the urgent demand for clean and renewable energy. One of the biggest challenges for PEM fuel cell technology is the high cost, attributed to the use of precious platinum group metals (PGM), e.g., Pt, particularly at cathodes where sluggish oxygen reduction reaction takes place. Two primary ways have been paved to address this cost challenge: one named low-loading PGM-based catalysts and another one is non-precious metal-based or PGM-free catalysts. Particularly for the PGM-free catalysts, tremendous efforts have been made to improve the performance and durability—milestones have been achieved in the corresponding PEM fuel cells. Even though the current status is still far from meeting the expectations. More efforts are thus required to further research and develop the desired PGM-free catalysts for cathodes in PEM fuel cells. Herein, this paper discusses the most recent progress of PGM-free catalysts and their applications in the practical membrane electrolyte assembly and PEM fuel cells. The most promising directions for future research and development are pointed out in terms of enhancing the intrinsic activity, reducing the degradation, as well as the study at the level of fuel cell stacks.

Substantial cost reduction is needed to commercialize polymer electrolyte fuel cells. As PGM catalysts are projected to account for ~42% cost of a fuel cell stack (1), replacement of PGMs with PGM-free catalysts is an attractive route to cost reduction. Over the past decade, extensive research efforts have led to significant improvements in kinetic activity (2), but conventional PGM-free catalyst continues to have lower volumetric activity than PGM catalysts. The lower volumetric activity requires use of a thicker cathode catalyst layer (CL), resulting in significant proton and oxygen transport losses (3). Therefore, along with kinetic improvements in oxygen reduction reaction, improved transport of H+ and O2 is needed to achieve performance comparable to PGM catalyst. In this study, we adopt a micro-patterning technique to incorporate non-tortuous ionomer channels in the cathode to increase the ionic conductivity of the thick catalyst layer. As shown in Figure 1, cathode ionomer channels enable rapid transportation of H+ throughout the catalyst layer, compared to thin and tortuous ionomer films in the conventional electrode. Polarization curves obtained in H2/air show significantly higher performance for the CL with ionomer channels compared to the conventional cathode. Electrochemical impedance spectroscopy data in H2/N2 also demonstrate a significant decrease in H+ resistance in the catalyst layer. The ionomer channels lead to a reduction in the H+ transport resistance, reducing ohmic overpotential in the catalyst layer. Further improvement in performance in the mass transport region is achieved through implementing optimized design of the dedicated ionomer channel. Acknowledgment This research was supported by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and the LANL LDRD program. References D. Papageorgopoulos, DOE Hydrogen and Fuel Cells Program FY2019 Annual Merit Review Proceedings, https://www.hydrogen.energy.gov/pdfs/review19/plenary_fuel_cell_papageorgopoulos_2019.pdf (2019). H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao and G. Wu, (2017). S. Komini Babu, H. T. Chung, P. Zelenay and S. Litster, ACS Appl Mater Interfaces, 8, 32764-32777 (2016). Figure 1

The continued depletion of strategic resources like fossil fuels, precious metals and other critical raw materials has put the world economy on the brink of a global crisis. Together with this, the continued emission of large amounts of greenhouse gases represents a significant challenge due to the effects of climate change. It is therefore imperative to find alternatives to fossil fuels that are sustainable, keeping in mind a full life cycle analysis. Clean technologies such as fuel cells and water electrolysis will be a fundamental part of the transition to renewable energy. In this context, a key role will be played by molecular hydrogen as “energy vector”. Thanks to its high specific energy density and clean combustion to water, H2 represents a high-quality energy carrier and an ideal candidate to replace fossil fuels. Importantly, H2 can be produced by water electrolysis and can be converted into electricity using Fuel Cells. However, low conversion efficiencies and high capital investment costs, still limit the use of these electrochemical technologies. The search for sustainable, stable, and active electrocatalysts will play a key role in reaching the performance required for these devices. The development and characterisation of such materials is the subject of the research described in this thesis. The first part of this thesis provides an introduction to the field, including a short overview of key electrochemical concepts, and a definition of the two types of devices that are studied, fuel cells and electrolyzers, and their respective anodic and cathodic reactions (Chapter 2). The synthesis and the chemical-physical characterization of all electrocatalysts is reported in Chapter 3. The electrochemical study of these materials in half-cells and their application in complete devices, are described in detail in Chapters 4, 5 and 6. Chapter 4, describes a study of the effect of metal-CeO2 interactions in carbon supported electrocatalysts on alkaline hydrogen oxidation and evolution reactions. A series of transition metal nanoparticle electrocatalysts (Pd, Ir, Ru and Rh) with a metal loading of 10 wt%, were prepared using two supports; carbon and carbon-CeO2 (50:50). Each material is characterized using XRD, XPS, TEM and electrochemical tests, EIS and tafel analysis is performed in order to understand the HER and HOR activities. The presence of CeO2 enhances the activity of Pd, Ir and Rh. Ruthenium has superior activity in term of mass activity, specific activity and i0, both for HER and HOR. The HOR/HER exchange current (i0) of Ru/C has an average value of 106 A gMetal−1. Importantly, EIS and capacitance measurements show that CeO2 promotes catalyst utilization and lowers ionic resistance. Chapter 5 focuses on developing sustainable electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC). In this study a high-performance Pd-CeO2/C hydrogen oxidation reaction (HOR) catalyst is integrated into AEMFCs in combination with different Pt and Pt-free cathodes. A H2/O2 AEMFC peak power performance of 2 W cm–2 at 80 °C is obtained when using a Pt/C cathode (2 A cm–2 is achieved at a cell voltage of 0.6 V), which translates to 1 W cm–2 peak power density (0.7 A cm–2 is achieved at 0.6 V) at 60 °C with the switch to a cheap, critical raw material (CRM)-free Fe/C cathode catalyst. In Chapter 6.1, a molecular catalyst for hydrogen evolution was developed and tested in a Polymer Exchange Membrane (PEM) water electrolyser. The dinuclear Ru diazadiene olefin complex, [Ru2(OTf)(μ-H)(Me2dad)(dbcot)2], is shown to be an active catalyst for hydrogen evolution. When supported on high surface area carbon black and at 80 °C, [Ru2(OTf)(μ-H)(Me2dad)(dbcot)2]@C evolves hydrogen at the cathode of a PEM electrolysis cell (400 mA cm−2, 1.9 V). A remarkable turn over frequency (TOF) of 7800 molH2 molcatalyst−1 h−1 is maintained over 7 days of operation. A series of model reactions in homogeneous media and in electrochemical half cells, combined with DFT calculations, are used to rationalize the hydrogen evolution mechanism promoted by [Ru2(OTf)(μ-H)(Me2dad)(dbcot)2]. Lastly, in Chapter 6.2 the development of a non-precious metal cathode catalyst for Anion Exchange Membrane Water Electrolysis (AEMWE) is reported. This study investigates an active HER catalyst synthesized from MoNiO4 nano-rod arrays on nickel foam using high-temperature reductive annealing. Complete characterization of the nanostructure by SEM, HR-TEM and XPS indicates that during synthesis the crystalline MoNiO4 structure of individual rods segregates a surface enriched polycrystalline MoO2 layer rather than a Ni4Mo alloy as reported previously. Mo and Ni electrochemical dissolution was studied by the scanning flow cell technique coupled with inductively coupled plasma mass spectrometry (SFC-ICP-MS). It was found that only Mo undergoes detectable dissolution phenomena, with the MoO2/Ni cathode prepared at 600°C being the most stable. Tests in an AEMWE with a Ni foam anode demonstrate a current density of 0.55 A cm-2 (2 V) at 60 °C and H2 production was stable for more than 300 h (0.5 A cm-2). The synthesis procedure was scaled up to prepare electrodes with an area of 78.5 cm2 that were employed and evaluated in a three-cell AEM electrolyser stack. In conclusion, the research described in this thesis demonstrates how engineering at the nanoscale can be used to improve the electrocatalytic activity and stability of sustainable catalytic materials for both fuel cells and electrolysers. The work conducted here has also gone beyond the study of materials on a lab scale, describing the scale up and application of electrocatalysts in actual devices.

La reazione di riduzione dell’ossigeno (ORR) è una reazione alla base di processi vitali, come la respirazione, e di sistemi di conversione energetica, come celle a combustibile e batterie metallo-aria. La riduzione d’ossigeno in soluzione acquosa avviene attraverso due meccanismi: “4 elettroni”, in cui O2 viene ridotto ad acqua, o “2 elettroni”, in cui il prodotto è H2O2. I catalizzatori a base di platino (PGM) sono considerati i migliori materiali per la catalisi di ORR, ma la loro applicazione in ambito industriale è ostacolata dall’elevato costo e dalla ridotta disponibilità del platino. Come alternativa, sono emersi catalizzatori privi di platino basati su complessi metallici (PGM-free). Questi elettrocatalizzatori sono promettenti sia in termini di attività catalitica sia di convenienza economica. Tra tutti i materiali PGM-free, maggiore interesse è stato dato ai complessi dei metalli di transizione del tipo M-N4, in particolare a base di ferro. Dunque, i catalizzatori FeN4 presentano molteplici vantaggi: basso costo, nuova reattività (possono catalizzare utili reazioni di ossi-riduzione) e modulabilità (lo stato elettronico del centro metallico può essere modulato sia modificando il suo intorno chimico con diversi tipi di leganti sia scegliendo supporti con diverse proprietà strutturali). Nonostante questi vantaggi, la bassa stabilità e densità dei siti attivi hanno impedito la loro diffusione su larga scala. Infatti, per ottenere un buon catalizzatore è importante la relazione tra i difetti intrinseci e le proprietà porose del supporto: i difetti di bordo, come FeN2+2, N-FeN2+2 e azoto piridinico, sono presenti nei micropori, mente i difetti nel piano (azoto grafitico e FeN4) sono situati nei mesopori. Per aumentare la stabilità è necessario aumentare il grado di grafitizzazione del supporto, per esempio attraverso trattamenti ad alta temperatura (> 600 °C). Un altro importante parametro è la selettività, ovvero la capacità di produrre principalmente acqua o acqua ossigenata. Quest’ultima può essere utilizzata come agente ossidante sostenibile per diversi scarti industriali. Riveste un ruolo fondamentale in processi avanzati di ossidazione (AOPs), come il metodo di Fenton, in cui l’acqua ossigenata viene usata per produrre radicali ●OH capaci di degradare inquinanti organici persistenti (POPs). Una maggiore efficacia di degradazione è ottenuta utilizzando metodi elettrochimici avanzati di ossidazione (EAOPs), in cui l’acqua ossigenata è prodotta in situ. In questa tesi di dottorato, sono stati sintetizzati diversi tipi di supporti carboniosi con diverse proprietà strutturali e diversi gradi di dopaggio con eteroatomi. L’influenza delle proprietà porose e la presenza di eteroatomi è stata valutata con molteplici tecniche: TEM, Raman, analisi elementare, ICP-MS, XPS, XRD. Grande attenzione è stata dedicata alla correlazione tra le prestazioni catalitiche e le proprietà porose, analizzate con la tecnica di adsorbimento/desorbimento di N2 a 77K. L’attività catalitica è stata valutata utilizzando tecniche elettrochimiche, come la tecnologia con elettrodo ad anello e disco rotanti (RRDE), necessaria per la determinazione della selettività. Sono stati testati diversi supporti: commerciali, ottenuti per hard-template, attivati con vapore/CO2, e ottenuti da precursori non convenzionali, quali biomasse e plastiche industriali. Gli svantaggi principali di quest’ultimi sono la ridotta stabilità e attività. Il migliore catalizzatore del tipo FeNx è stato sintetizzato da un supporto carbonioso dopato zolfo ottenuto attraverso hard-template e attivato con vapore. Questo materiale presenta E1/2 = 0.739 VRHE, jK = 1.02 mA cm-2 a 0.80 VRHE e una produzione del 3 % di H2O2. Quindi, maggiore attenzione deve essere data allo studio dell’interazione tra il centro metallico e il supporto, in modo tale da capire come aumentare la densità dei siti attivi realmente coinvolti durante la reazione di riduzione dell’ossigeno.