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Yoon, Ji Sun, Min Bum Park, Youngmin Kim, Dong Won Hwang i Ho-Jeong Chae. "Effect of Metal Oxide–Support Interactions on Ethylene Oligomerization over Nickel Oxide/Silica–Alumina Catalysts". Catalysts 9, nr 11 (8.11.2019): 933. http://dx.doi.org/10.3390/catal9110933.
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We investigated the interactions between nickel oxide and silica–alumina supports, which were applied to the catalytic oligomerization of ethylene by powder X-ray diffraction, UV diffuse reflectance spectroscopy, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic activity was also correlated with the acidity of catalysts determined by NH3 temperature-programmed desorption and pyridine FT-IR spectroscopy. Although all the catalysts had similar Ni contents, their catalytic performances were strongly influenced by the strength of the metal oxide–support interaction. Strong interaction promoted the formation of nickel aluminate on the catalyst surface, and resulted in low catalytic activity due to reducing the amount of nickel oxide active sites. However, weak interaction favored the aggregation of nickel oxide species into larger particles, and thus resulted in low ethylene conversion and selectivity to oligomers. Eventually, the optimal activity was realized at the medium interaction strength, preserving a high amount of both active nickel oxides and acid sites.
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Charisiou, Nikolaos, Savvas Douvartzides, Georgios Siakavelas, Lazaros Tzounis, Victor Sebastian, Vlad Stolojan, Steven Hinder, Mark Baker, Kyriaki Polychronopoulou i Maria Goula. "The Relationship between Reaction Temperature and Carbon Deposition on Nickel Catalysts Based on Al2O3, ZrO2 or SiO2 Supports during the Biogas Dry Reforming Reaction". Catalysts 9, nr 8 (9.08.2019): 676. http://dx.doi.org/10.3390/catal9080676.
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The tackling of carbon deposition during the dry reforming of biogas (BDR) necessitates research of the surface of spent catalysts in an effort to obtain a better understanding of the effect that different carbon allotropes have on the deactivation mechanism and correlation of their formation with catalytic properties. The work presented herein provides a comparative assessment of catalytic stability in relation to carbon deposition and metal particle sintering on un-promoted Ni/Al2O3, Ni/ZrO2 and Ni/SiO2 catalysts for different reaction temperatures. The spent catalysts were examined using thermogravimetric analysis (TGA), Raman spectroscopy, high angle annular dark field scanning transmission electron microscopy (STEM-HAADF) and X-ray photoelectron spectroscopy (XPS). The results show that the formation and nature of carbonaceous deposits on catalytic surfaces (and thus catalytic stability) depend on the interplay of a number of crucial parameters such as metal support interaction, acidity/basicity characteristics, O2– lability and active phase particle size. When a catalytic system possesses only some of these beneficial characteristics, then competition with adverse effects may overshadow any potential benefits.
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El-Salamony, Radwa A., Ahmed S. Al-Fatesh, Kenit Acharya, Abdulaziz A. M. Abahussain, Abdulaziz Bagabas, Nadavala Siva Kumar, Ahmed A. Ibrahim, Wasim Ullah Khan i Rawesh Kumar. "Carbon Dioxide Valorization into Methane Using Samarium Oxide-Supported Monometallic and Bimetallic Catalysts". Catalysts 13, nr 1 (4.01.2023): 113. http://dx.doi.org/10.3390/catal13010113.
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Samarium oxide (Sm2O3) is a versatile surface for CO2 and H2 interaction and conversion. Samarium oxide-supported Ni, samarium oxide-supported Co-Ni, and samarium oxide-supported Ru-Ni catalysts were tested for CO2 methanation and were characterized by X-ray diffraction, nitrogen physisorption, infrared spectroscopy, H2-temperature programmed reduction, and X-ray photoelectron spectroscopy. Limited H2 dissociation and widely available surface carbonate and formate species over 20 wt.% Ni, dispersed over Sm2O3, resulted in ~98% CH4 selectivity. The low selectivity for CO could be due to the reforming reaction between CH4 (methanation product) and CO2. Co-impregnation of cobalt with nickel over Sm2O3 had high surface adsorbed oxygen and higher CO selectivity. On the other hand, co-impregnation of ruthenium and nickel over Sm2O3 led to more than one catalytic active site, carbonate species, lack of formate species, and 94% CH4 selectivity. It indicated the following route of CH4 synthesis over Ru-Ni/Sm2O3; carbonate → unstable formate → CO → CH4.
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Todorova, Silviya, Anton Naydenov, Maya Shopska, Hristo Kolev, Iliyana Yordanova i Krasimir Tenchev. "Pt-Modified Nano-Sized Mn2O3 Oxide Prepared from the Mn3O4 Phase with Tetragonal Symmetry for CO Oxidation". Symmetry 14, nr 12 (1.12.2022): 2543. http://dx.doi.org/10.3390/sym14122543.
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One of the current problems in the environmental catalysis is the design of an effective and less costly catalytic system for the oxidation of CO. The nano-sized α-Mn2O3 oxide has been prepared and modified with 0.5 wt.% Pt. The catalysts have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), temperature-programmed reduction (TPR) and diffuse-reflectance infrared spectroscopy (DRIFTS). Finely divided PtO and Pt(OH)2 are being formed on the Mn2O3 surface as a result of the strong interaction between platinum and the nano-oxide. Based on DRIFTS investigations and the model calculations, a Langmuir–Hinshelwood type of mechanism is supposed for CO oxidation on Pt/Mn2O3. The CO and oxygen are adsorbed on different types of sites. The Mars–van Krevelen mechanism is the most probable one over pure Mn2O3, thus suggesting that CO2 is adsorbed on the oxidized sites. The CO adsorption in the mixture CO + N2 or in the presence of oxygen (CO + N2 + O2) leads to a partial reduction in the Pt+ surface species and the formation of linear Pt1+−CO and Pt0−CO carbonyls. Both of them take part in the CO oxidation reaction.
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Siemer, Michael, Lars Mohrhusen, Maximilian Grebien i Katharina Al-Shamery. "Amine Capped Gold Colloids at Oxidic Supports: Their Electronic Interactions". Zeitschrift für Physikalische Chemie 233, nr 1 (19.12.2018): 69–84. http://dx.doi.org/10.1515/zpch-2018-0004.
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Abstract Colloidal deposition of noble metal nanoparticles on oxidic supports is a recent approach for the fabrication of heterogeneous catalyst materials. We present studies on the interaction of different amine ligands with gold nanoparticles before and after deposition on several oxidic supports (titania, silica, alumina, magnesia or zinc oxide), using X-ray photoelectron and Auger spectroscopy, and high-resolution transmission electron microscopy. The adsorption of amines on thin gold films as well as on nanoparticles leads to a decrease in metal photoelectron binding energies. Usually, this is explained by donor-acceptor interactions via the amine group. By additional analysis of Auger signals, which are more sensitive to changes in the oxidation state than photoelectron spectra, we demonstrate that these shifts are due to a final state effect, namely, the increased photoelectron hole screening in presence of amine adsorbates. It will be shown, that this effect is not sensitive neither to the nanoparticle size nor the sterical properties of the capping amine. After deposition on oxide supports, the photoelectron binding energies are even further decreased. The presented findings exhibit that care has to be taken to interpret binding energy shifts simply with charging, which has impact on understanding the local electronic situation on the surface of metal-loaded oxides, crucial for heterogeneous catalysis.
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Chuai, Hongyuan, Penghe Su, Hongchi Liu, Baolin Zhu, Shoumin Zhang i Weiping Huang. "Alkali and Alkaline Earth Cation-Decorated TiO2 Nanotube-Supported Rh Catalysts for Vinyl Acetate Hydroformylation". Catalysts 9, nr 2 (20.02.2019): 194. http://dx.doi.org/10.3390/catal9020194.
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Alkali and alkaline earth cation-decorated TiO2 nanotube (TNT)-supported rhodium catalysts were synthesized and characterized by inductively-coupled plasma optical emission spectrometer, surface characterization analyzer, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transforming infrared spectrum, respectively. Their catalytic performances were evaluated by the hydroformylation of vinyl acetate. Results showed that both the conversion rate of vinyl acetate and selectivity for aldehyde were improved after Rh/TNTs were modified by alkali or alkali-earth cations. Such improved selectivity for aldehyde might be attributed to the presence of alkali or alkaline earth cations which enhanced CO adsorption, while the high conversion rate of vinyl acetate was likely due to the proper interaction of Lewis acid–base between cations modified TNTs and vinyl acetate.
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Zhao, Feng, Shuangde Li, Xiaofeng Wu, Renliang Yue, Weiman Li, Xicuo Zha, Yuzhou Deng i Yunfa Chen. "Catalytic Behaviour of Flame-Made CuO-CeO2 Nanocatalysts in Efficient CO Oxidation". Catalysts 9, nr 3 (13.03.2019): 256. http://dx.doi.org/10.3390/catal9030256.
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CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g−1 × h−1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.
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Fazlikeshteli, Shiva, Xavier Vendrell i Jordi Llorca. "Low-Temperature Methane Partial Oxidation over Pd Supported on CeO2: Effect of the Preparation Method and Precursors". Reactions 2, nr 1 (17.02.2021): 30–42. http://dx.doi.org/10.3390/reactions2010004.
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The catalytic production of syngas by the partial oxidation of methane (POM) was investigated over Pd supported on ceria (0.5–2 Pd wt.%) prepared by incipient wetness impregnation and by mechanochemical methods. The performance of the Pd/CeO2 catalyst prepared by milling CeO2 and Pd acetate was superior to that prepared by milling CeO2 and Pd nitrate and to Pd/CeO2 prepared by impregnation from Pd acetate. The best catalytic activity of the Pd/CeO2 catalyst prepared from CeO2 and Pd acetate was obtained by milling at 50 Hz for 5 min. Two-step combustion and reforming reaction mechanism were identified. Remarkably, methane conversion increased progressively with Pd loading for the catalysts prepared by incipient wetness impregnation, whereas low metal loading showed better conversion of methane for the catalysts prepared by ball milling using Pd acetate. This was explained in terms of an impressive dispersion of Pd species with a strong interaction with the surface of ceria, as deduced from transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy characterization, which revealed a large quantity of highly oxidized species at the surface.
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Filip, Mihaela, Elena Maria Anghel, Vasile Rednic, Florica Papa, Simona Somacescu, Cornel Munteanu, Nicolae Aldea, Jing Zhang i Viorica Parvulescu. "Variation in Metal–Support Interaction with TiO2 Loading and Synthesis Conditions for Pt-Ti/SBA-15 Active Catalysts in Methane Combustion". Nanomaterials 13, nr 10 (15.05.2023): 1647. http://dx.doi.org/10.3390/nano13101647.
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The control of catalytic performance using synthesis conditions is one of the main goals of catalytic research. Two series of Pt-Ti/SBA-15 catalysts with different TiO2 percentages (n = 1, 5, 10, 30 wt.%) were obtained from tetrabutylorthotitanate (TBOT) and peroxotitanate (PT), as titania precursors and Pt impregnation. The obtained catalysts were characterized using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), N2 sorption, Raman, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), hydrogen temperature-programmed reduction (H2-TPR) and H2-chemisorption measurements. Raman spectroscopy showed framework titanium species in low TiO2 loading samples. The anatase phase was evidenced for samples with higher titania loading, obtained from TBOT, and a mixture of rutile and anatase for those synthesized by PT. The rutile phase prevails in rich TiO2 catalysts obtained from PT. Variable concentrations of Pt0 as a result of the stronger interaction of PtO with anatase and the weaker interaction with rutile were depicted using XPS. TiO2 loading and precursors influenced the concentration of Pt species, while the effect on Pt nanoparticles’ size and uniform distribution on support was insignificant. The Pt/PtO ratio and their concentration on the surface were the result of strong metal–support interaction, and this influenced catalytic performance in the complete oxidation of methane at a low temperature. The highest conversion was obtained for sample prepared from PT with 30% TiO2.
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Kong, Weimin, Shuyuan Zhou, Xuwei Wang, Qingrong He, Piaoping Yang, Ye Yuan i Yanchun Dong. "Catalytic Oxidative Decomposition of Dimethyl Methyl Phosphonate over CuO/CeO2 Catalysts Prepared Using a Secondary Alkaline Hydrothermal Method". Catalysts 12, nr 10 (19.10.2022): 1277. http://dx.doi.org/10.3390/catal12101277.
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Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 lattice. The physical and chemical properties of CeO2, CuO/CeO2, and CuO were investigated. H2 temperature-programmed reduction characterization showed that the oxidation activity of CuO/CeO2 was significantly improved. X-ray photoelectron spectroscopy results showed that electron transfer occurred between Ce and Cu in the CuO/CeO2 catalyst. Additionally, Raman characterization confirmed the strong interaction between Cu and Ce. After CuO was loaded, the thermal catalytic decomposition performance of the catalyst was significantly improved with respect to the sarin simulant dimethyl methyl phosphonate (DMMP); with an increase in the Cu/Ce ratio, the performance first strengthened and then weakened. Additionally, the reaction tail gas and catalyst surface products were analyzed using mass spectrometry and ion chromatography, and the changes in the surface products during the thermal catalytic decomposition of DMMP were characterized at different temperatures using in situ diffuse reflectance infrared Fourier transform spectroscopy. Finally, the catalytic reaction pathways of DMMP on CeO2, CuO/CeO2, and CuO were inferred. The study results not only demonstrate an effective catalyst for the removal of nerve agent but also a feasible preparation method for lattice-doped bimetallic catalysts in the field of environmental protection.
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Lambert, Joseph B., Liang Xue, Richard J. Bosch, Kalulu M. Taba, Dale E. Marko, Shigeyuki Urano i Pierre R. LeBreton. "Through-space interactions of double bonds by photoelectron spectroscopy". Journal of the American Chemical Society 108, nr 24 (listopad 1986): 7575–79. http://dx.doi.org/10.1021/ja00284a022.
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Al-Doghachi, Faris A. Jassim, Diyar M. A. Murad, Huda S. Al-Niaeem, Salam H. H. Al-Jaberi, Surahim Mohamad i Yun Hin Taufiq-Yap. "High Active Co/Mg1-xCex3+O Catalyst: Effects of Metal-Support Promoter Interactions on CO2 Reforming of CH4 Reaction". Bulletin of Chemical Reaction Engineering & Catalysis 16, nr 1 (8.02.2021): 97–110. http://dx.doi.org/10.9767/bcrec.16.1.9969.97-110.
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Co/Mg1−XCe3+XO (x = 0, 0.03, 0.07, 0.15; 1 wt% cobalt each) catalysts for the dry reforming of methane (DRM) reaction were prepared using the co-precipitation method with K2CO3 as precipitant. Characterization of the catalysts was achieved by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (H2-TPR), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA). The role of several reactant and catalyst concentrations, and reaction temperatures (700–900 °C) on the catalytic performance of the DRM reaction was measured in a tubular fixed-bed reactor under atmospheric pressure at various CH4/CO2 concentration ratios (1:1 to 2:1). Using X-ray diffraction, a surface area of 19.2 m2.g−1 was exhibited by the Co/Mg0.85Ce3+0.15O catalyst and MgO phase (average crystallite size of 61.4 nm) was detected on the surface of the catalyst. H2 temperature programmed reaction revealed a reduction of CoO particles to metallic Co0 phase. The catalytic stability of the Co/Mg0.85Ce3+0.15O catalyst was achieved for 200 h on-stream at 900 °C for the 1:1 CH4:CO2 ratio with an H2/CO ratio of 1.0 and a CH4, CO2 conversions of 75% and 86%, respectively. In the present study, the conversion of CH4 was improved (75%–84%) when conducting the experiment at a lower flow of oxygen (1.25%). Finally, the deposition of carbon on the spent catalysts was analyzed using TEM and Temperature programmed oxidation-mass spectroscopy (TPO-MS) following 200 h under an oxygen stream. Better anti-coking activity of the reduced catalyst was observed by both, TEM, and TPO-MS analysis. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
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Scarano, Antonio, Felice Lorusso, Tiziana Orsini, Marco Morra, Giorgio Iviglia i Luca Valbonetti. "Biomimetic Surfaces Coated with Covalently Immobilized Collagen Type I: An X-Ray Photoelectron Spectroscopy, Atomic Force Microscopy, Micro-CT and Histomorphometrical Study in Rabbits". International Journal of Molecular Sciences 20, nr 3 (8.02.2019): 724. http://dx.doi.org/10.3390/ijms20030724.
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Background: The process of osseointegration of dental implants is characterized by healing phenomena at the level of the interface between the surface and the bone. Implant surface modification has been introduced in order to increase the level of osseointegration. The purpose of this study is to evaluate the influence of biofunctional coatings for dental implants and the bone healing response in a rabbit model. The implant surface coated with collagen type I was analyzed through X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), micro-CT and histologically. Methods: The sandblasted and double acid etched surface coated with collagen type I, and uncoated sandblasted and double acid etched surface were evaluated by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) analysis in order evaluate the different morphology. In vivo, a total of 36 implants were positioned in rabbit articular femoral knee-joint, 18 fixtures for each surface. Micro-CT scans, histological and histomorphometrical analysis were conducted at 15, 30 and 60 days. Results: A histological statistical differences were evident at 15, 30 and 60 days (p < 0.001). Both implant surfaces showed a close interaction with newly formed bone. Mature bone appeared in close contact with the surface of the fixture. The AFM outcome showed a similar roughness for both surfaces. Conclusion: However, the final results showed that a coating of collagen type I on the implant surface represents a promising procedure able to improve osseointegration, especially in regions with a low bone quality.
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Slepička, Petr, Silvie Rimpelová, Vladimíra Svobodová Pavlíčková, Nikola Slepičková Kasálková, Klaudia Hurtuková, Dominik Fajstavr i Václav Švorčík. "Mammalian Cell Interaction with Periodic Surface Nanostructures". International Journal of Molecular Sciences 23, nr 9 (23.04.2022): 4676. http://dx.doi.org/10.3390/ijms23094676.
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Here, we report on the nanopatterning of different aromatic polymer substrates achieved by KrF excimer laser treatment. The conditions for the construction of the laser-induced periodic surface structures, the so-called LIPSS pattern, were established by optimized laser fluence and a number of pulses. The polymer substrates were polyethylene naphthalate (PEN), polyethersulfone (PES), and polystyrene (PS), which were chosen since they are thermally, chemically, and mechanically resistant polymers with high absorption coefficients at the excimer laser wavelength. The surface morphology of the treated substrates was investigated by atomic force microscopy and scanning electron microscopy, and the roughness and effective surface area on the modified samples were determined. Elemental concentration was characterized by energy-dispersive (EDX) analysis, surface chemistry was determined with X-ray photoelectron spectroscopy (XPS). The samples with the formation of LIPSS induced by 10 mJ·cm−2 with 1000, 3000, and 6000 pulses were used for subsequent in vitro cytocompatibility tests using human cells from osteosarcoma (U-2 OS). The LIPSS pattern and its ability of significant cell guidance were confirmed for some of the studied samples. Cell morphology, adhesion, and proliferation were evaluated. The results strongly contribute to the development of novel applications using nanopatterned polymers, e.g., in tissue engineering, cell analysis or in combination with metallization for sensor construction.
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Jung, Jae-Won, Won-Il Kim, Jeong-Rang Kim, Kyeongseok Oh i Hyoung Lim Koh. "Effect of Direct Reduction Treatment on Pt–Sn/Al2O3 Catalyst for Propane Dehydrogenation". Catalysts 9, nr 5 (14.05.2019): 446. http://dx.doi.org/10.3390/catal9050446.
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Pt–Sn/Al2O3 catalysts were prepared by the direct reduction method at temperatures from 450 to 900 °C, denoted as an SR series (SR450 to SR900 according to reduction temperature). Direct reduction was performed immediately after catalyst drying without a calcination step. The activity of SR catalysts and a conventionally prepared (Cal600) catalyst were compared to evaluate its effect on direct reduction. Among the SR catalysts, SR550 showed overall higher conversion of propane and propylene selectivity than Cal600. The nano-sized dispersion of metals on SR550 was verified by transmission electron microscopy (TEM) observation. The phases of the bimetallic Pt–Sn alloys were examined by X-ray diffraction, TEM, and energy dispersive X-ray spectroscopy (EDS). Two characteristic peaks of Pt3Sn and PtSn alloys were observed in the XRD patterns, and these phases affected the catalytic performance. Moreover, EDS confirmed the formation of Pt3Sn and PtSn alloys on the catalyst surface. In terms of catalytic activity, the Pt3Sn alloy showed better performance than the PtSn alloy. Relationships between the intermetallic interactions and catalytic activity were investigated using X-ray photoelectron spectroscopy. Furthermore, qualitative analysis of coke formation was conducted after propane dehydrogenation using differential thermal analysis.
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Kirichenko, Olga A., Elena A. Redina, Gennady I. Kapustin, Marina S. Chernova, Anastasiya A. Shesterkina i Leonid M. Kustov. "Facile Redox Synthesis of Novel Bimetallic Crn+/Pd0 Nanoparticles Supported on SiO2 and TiO2 for Catalytic Selective Hydrogenation with Molecular Hydrogen". Catalysts 11, nr 5 (30.04.2021): 583. http://dx.doi.org/10.3390/catal11050583.
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The bimetallic Crn+/Pd0 nanoparticles have been synthesized for the first time by a two-step redox method. The method includes the deposition of Pd0 nanoparticles on the surface of SiO2 and TiO2 carriers followed by the deposition of Crn+ on the surface of Pd0 nanoparticles using the redox procedures, which are based on the catalytic reduction of Crn+ with H2 in aqueous suspensions at ambient conditions. Transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourie-transformed infrared spectroscopy of adsorbed CO (FTIR-CO), and CO chemisorption studies were performed to characterize the morphology, nanoparticle size, element, and particle distribution, as well as the electronic state of deposited metals in the obtained catalysts. A decrease in nanoparticle size from 22 nm (Pd/SiO2) to 2–6 nm (Pd/TiO2) makes possible deposition of up to 1.1 wt.% Cr most likely as Cr3+. The deposition of CrOx species on the surface of Pd nanoparticles was confirmed using FTIR of adsorbed CO and the method of temperature-programmed reduction with hydrogen (TPR-H2). The intensive hydrogen consumption in the temperature ranges from −50 °C to 40 °C (Cr/Pd/SiO2) and from −90 °C to −40 °C (Cr/Pd/TiO2) was first observed for the supported Pd catalysts. The decrease in the temperature of β-PdHx decomposition indicates the strong interaction between the deposited Crn+ species and Pd0 nanoparticle after reduction with H2 at 500 °C. The novel Crn+/Pd/TiO2 catalysts demonstrated a considerably higher activity in selective hydrogenation of phenylacetylene than the Pd/TiO2 catalyst at ambient conditions.
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Barakat, Tarek, Joanna Rooke, Dayan Chlala, Renaud Cousin, Jean-François Lamonier, Jean-Marc Giraudon, Sandra Casale, Pascale Massiani, Bao-Lian Su i Stéphane Siffert. "Oscillatory Behavior of Pd-Au Catalysts in Toluene Total Oxidation". Catalysts 8, nr 12 (22.11.2018): 574. http://dx.doi.org/10.3390/catal8120574.
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In this work, the activity of bimetallic Pd-Au doped hierarchically structured titania catalysts has been investigated in the total oxidation of toluene. In earlier works, doping titania with group Vb metal oxides ensured an increased catalytic performance in the elimination of VOC molecules. A synergy between gold and palladium loaded at the surface of titania supports provided better performances in VOC oxidation reactions. Therefore, the main focus in this work was to investigate the durability of the prepared catalysts under long time-on-stream periods. Vanadium-doped catalysts showed a stable activity throughout the whole 110 h test, whereas, surprisingly, niobium-doped catalysts presented a cycle-like activity while nevertheless maintaining a high performance in toluene elimination. Operando Diffuse Reflectance Infrared Fourrier Transform spectroscopy (DRIFT) experiments revealed that variations in the presence of OH radicals and the presence of carbonaceous compounds adsorbed at the surface of spent catalysts varies with the occurrence of oscillations. X-ray Photoelectron Spectroscopy (XPS) results show that interactions between the material and the active phase provided extra amounts of mobile oxygen species and participated in easing the reduction of palladium. An enhanced redox reaction scheme is thus obtained and allows the occurrence of the cyclic-like performance of the catalyst.
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Lyman, C. E. "Analysis of Surface species in a Co/La/alumina catalyst". Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 702–3. http://dx.doi.org/10.1017/s0424820100105576.
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Lanthanum oxide is sometimes used as a promoter for Co-based CO hydrogenation catalysts. However, there is evidence that a high La content decreases catalyst activity and shifts catalyst selectivity. Analysis of such a catalyst by x-ray photoelectron spectroscopy(XPS), Raman spectroscopy, and powder x-ray diffraction suggested the formation of a surface Co-La interaction species. Unfortunately, interpretation of XPS data alone can be difficult if the surface is covered with several compounds of different composition and size. In the present case, there was a need to determine the composition of the surface Co-La interaction species without interference from other compounds containing Co and/or La. Analytical electron microscopy (AEM) is a technique that can provide information about the composition of the catalyst in specific regions of the catalyst surface between the other phases that may be present. Digital x-ray mapping was used here to locate the catalyst areas,free of interfering Co-La compounds,where analysis of the Co-La surface species can be made.
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Spasov, Ivanova, Pushkarev, Pushkareva, Presnyakova, Chumakov, Presnyakov, Grigoriev i Fateev. "On the Influence of Composition and Structure of Carbon-Supported Pt-SnO2 Hetero-Clusters onto Their Electrocatalytic Activity and Durability in PEMFC". Catalysts 9, nr 10 (25.09.2019): 803. http://dx.doi.org/10.3390/catal9100803.
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A detailed study of the structure, morphology and electrochemical properties of Pt/C and Pt/x-SnO2/C catalysts synthesized using a polyol method has been provided. A series of catalysts supported on the SnO2-modified carbon was synthesized and studied by various methods including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical methods, and fuel cell testing. The SnO2 content varies from 5 to 40 wt %. The TEM images, XRD and XPS analysis suggested the Pt-SnO2 hetero-clusters formation. The SnO2 content of ca. 10% ensures an optimal catalytic layer structure and morphology providing uniform distribution of Pt-SnO2 clusters over the carbon support surface. Pt/10wt %-SnO2/C catalyst demonstrates increased activity and durability toward the oxygen reduction reaction (ORR) in course of accelerated stress testing due to the high stability of SnO2 and its interaction with Pt. The polymer electrolyte membrane fuel cell current–voltage performance of the Pt/10wt %-SnO2/C is comparable with those of Pt/C, however, higher durability is expected.
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Kaplin, Igor Yu, Ekaterina S. Lokteva, Svetlana V. Bataeva, Konstantin I. Maslakov, Alexander V. Fionov, Alexey V. Shumyantsev, Oksana Ya Isaikina, Alexey O. Kamaev i Elena V. Golubina. "Effect of MnO x modification and template type on the catalytic performance of ceria-zirconia in CO and soot oxidation". Pure and Applied Chemistry 93, nr 4 (1.04.2021): 447–62. http://dx.doi.org/10.1515/pac-2020-1012.
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Abstract The effect of the template nature and modification with MnO x on the catalytic efficiency of Ce0.8Zr0.2O2 (CZ) in oxidation of CO (2 vol% CO and 1 vol% O2 in He, pulse feeding) and soot particles (tight contact between soot and catalyst, TGA/DSC) was analyzed. The CZ catalysts were prepared using the CTAB and sawdust (SD) templates and modified with Mn (8 wt%) by wet impregnation followed by calcination at 400 °С. SEM-EDS, XRD, Raman and photoelectron spectroscopy, N2 adsorption, EPR, TPR-H2 and catalytic tests results demonstrated better catalytic activity of CZ(SD) in CO oxidation than of CZ(CTAB) because of the biomorphic texture, higher structural defectiveness and improved oxygen mobility of the former catalyst. Low surface reducibility and low concentration of active oxygen species on the CZ(SD) surface deteriorated its catalytic efficiency in the topochemical reaction of soot oxidation. Despite the different structure and degree of interaction between MnO x and CZ, the Mn-modified catalysts showed the similar catalytic properties: much better than of both unmodified catalysts in CO oxidation and worse than of CZ(CTAB) in soot oxidation. Mn2+ ions incorporated better into the surface layer of CZ(SD) than of CZ(CTAB), for which the inhomogeneous distribution of MnO x and decreased specific surface area were observed.
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Chesnokov, Vladimir V., Vladimir V. Kriventsov, Igor P. Prosvirin i Evgeny Yu Gerasimov. "Effect of Platinum Precursor on the Properties of Pt/N-Graphene Catalysts in Formic Acid Decomposition". Catalysts 12, nr 9 (8.09.2022): 1022. http://dx.doi.org/10.3390/catal12091022.
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Properties of a novel catalytic material, Pt/N-graphene, in gas-phase decomposition of formic acid to obtain pure hydrogen were studied. The graphene powder doped with nitrogen atoms was used as the carbon support. The following methods were used to characterize the synthesized catalysts: X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), EXAFS and CO chemisorption. It was determined that the platinum precursor substantially affects the state of the metal in the Pt/N-graphene catalysts. When Pt(NO3)4 was used as the precursor, platinum on the catalyst surface was in the form of nanocrystals. Meanwhile, the use of H2PtCl6 led to the formation of atomically dispersed platinum stabilized on the surface of N-graphene. Carbon structures containing defects in the graphene layer surrounded by four nitrogen atoms had strong interactions with platinum atoms and acted as the sites where atomic platinum was stabilized.
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Duan, Xiaoxu, Jinxiao Dou, Yongqi Zhao, Salman Khoshk Rish i Jianglong Yu. "A Study on Mn-Fe Catalysts Supported on Coal Fly Ash for Low-Temperature Selective Catalytic Reduction of NOX in Flue Gas". Catalysts 10, nr 12 (30.11.2020): 1399. http://dx.doi.org/10.3390/catal10121399.
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A series of Mn0.15Fe0.05/fly-ash catalysts have been synthesized by the co-precipitation method using coal fly ash (FA) as the catalyst carrier. The catalyst showed high catalytic activity for low-temperature selective catalytic reduction (LTSCR) of NO with NH3. The catalytic reaction experiments were carried out using a lab-scale fixed-bed reactor. De-NOx experimental results showed the use of optimum weight ratio of Mn/FA and Fe/FA, resulted in high NH3-SCR (selective catalytic reduction) activity with a broad operating temperature range (130–300 °C) under 50000 h−1. Various characterization methods were used to understand the role of the physicochemical structure of the synthesized catalysts on their De-NOx capability. The scanning electron microscopy, physical adsorption-desorption, and X-ray photoelectron spectroscopy showed the interaction among the MnOx, FeOx, and the substrate increased the surface area, the amount of high valence metal state (Mn4+, Mn3+, and Fe3+), and the surface adsorbed oxygen. Hence, redox cycles (Fe3+ + Mn2+ ↔ Mn3+ + Fe2+; Fe2+ + Mn4+ ↔ Mn3+ + Fe3+) were co-promoted over the catalyst. The balance between the adsorption ability of the reactants and the redox ability can promote the excellent NOx conversion ability of the catalyst at low temperatures. Furthermore, NH3/NO temperature-programmed desorption, NH3/NO- thermo gravimetric-mass spectrometry (NH3/NO-TG-MS), and in-situ DRIFTs (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) results showed the Mn0.15Fe0.05/FA has relatively high adsorption capacity and activation capability of reactants (NO, O2, and NH3) at low temperatures. These results also showed that the Langmuir–Hinshelwood (L–H) reaction mechanism is the main reaction mechanism through which NH3-SCR reactions took place. This work is important for synthesizing an efficient and environmentally-friendly catalyst and demonstrates a promising waste-utilization strategy.
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Shi, Qi, Long Ding, Hong-Ming Long i Tie-Jun Chun. "Study of Catalytic Combustion of Dioxins on Ce-V-Ti Catalysts Modified by Graphene Oxide in Simulating Iron Ore Sintering Flue Gas". Materials 13, nr 1 (26.12.2019): 125. http://dx.doi.org/10.3390/ma13010125.
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Ce-V-Ti and Ce-V-Ti/GO catalysts synthesized by the sol-gel method were used for the catalytic combustion of dioxins at a low temperature under simulating sintering flue gas in this paper. The catalytic mechanism of Ce-V-Ti catalysts modified with graphene oxides (GO) at a low temperature was revealed through X-ray diffractometer (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2-TPR) and Fourier transform infrared (FTIR). During the tests, chlorobenzene (CB) was used as a model reagent since the dioxins are poisonous. The results showed that introducing GO to Ce-V-Ti catalysts can improve the specific surface area and promote the CB adsorption on the surface of catalysts. Simultaneously, the Ce-V-Ti with 0.7 wt % GO support showed the high activity with the conversion of 60% at 100 °C and 80% at 150 °C. The adsorb ability of catalysts is strengthened by the electron interaction between GO and CB through π-π bond. In the case of Ce-V-Ti catalysts, Ce played a major catalytic role and V acted as a co-catalytic composition. After GO modification, the concentration of Ce3+ and V4+ were enlarged. The synergy between Ce3+ and V3+ played the critical role on the low-temperature performance of catalysts under sintering flue gas.
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Liu, Ye, Chonglin Song, Gang Lv, Chenyang Fan i Xiaodong Li. "Promotional Effect of Cerium and/or Zirconium Doping on Cu/ZSM-5 Catalysts for Selective Catalytic Reduction of NO by NH3". Catalysts 8, nr 8 (28.07.2018): 306. http://dx.doi.org/10.3390/catal8080306.
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The cerium and/or zirconium-doped Cu/ZSM-5 catalysts (CuCexZr1−xOy/ZSM-5) were prepared by ion exchange and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR). Activities of the catalysts obtained on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia were measured using temperature programmed reactions. Among all the catalysts tested, the CuCe0.75Zr0.25Oy/ZSM-5 catalyst presented the highest catalytic activity for the removal of NO, corresponding to the broadest active window of 175–468 °C. The cerium and zirconium addition enhanced the activity of catalysts, and the cerium-rich catalysts exhibited more excellent SCR activities as compared to the zirconium-rich catalysts. XRD and TEM results indicated that zirconium additions improved the copper dispersion and prevented copper crystallization. According to XPS and H2-TPR analysis, copper species were enriched on the ZSM-5 grain surfaces, and part of the copper ions were incorporated into the zirconium and/or cerium lattice. The strong interaction between copper species and cerium/zirconium improved the redox abilities of catalysts. Furthermore, the introduction of zirconium abates N2O formation in the tested temperature range.
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Su, Qingfa, Xianfang Yi, Jifa Miao, Yanting Chen, Jinsheng Chen i Jinxiu Wang. "A Comparative Study in Vanadium and Tungsten Leaching from Various Sources of SCR Catalysts with Local Difference". Sustainability 12, nr 4 (18.02.2020): 1499. http://dx.doi.org/10.3390/su12041499.
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Direct leaching with NaOH can be an economically acceptable method for vanadium (V) and tungsten (W) recovery from spent selective catalytic reduction (SCR) catalysts. However, different chemical-physical characteristics of catalysts would affect the V and W leaching. In this paper, the V and W leaching behavior of various sources of SCR catalysts with a local difference (yellow and gray color) were systematically investigated with alkali leaching solution under ambient pressure. Different leaching efficiencies from yellow and gray color areas were correlated with oxidation states and species of V and W on catalyst surfaces, as characterized by X-ray photoelectron spectroscopy (XPS), Raman, Fourier transform infrared spectroscopy (FTIR), and other analytic methods. For the V leaching efficiency, the samples from a gray area of catalysts (40.0–51.0%) were lower than that from the yellow area (66.8–69.8%). The higher molar ratio of V3+ and a lower molar ratio of V5+, and the lower total V content on the surface of the samples from the gray area could be the main reasons for the lower V leaching efficiency. As for the W leaching efficiency, the samples from the gray area (44.6–57.3%) were slightly higher than that from the yellow area (38.0–52.6%) of catalysts. The less total W content of surface species and stronger interaction among V–W–Ti of yellow area samples resulted in the lower leaching efficiency. These differential leaching efficiencies needed to be taken into consideration for recovering V and W from spent SCR catalysts.
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Gieroba, Barbara, Anna Sroka-Bartnicka, Paulina Kazimierczak, Grzegorz Kalisz, Agnieszka Lewalska-Graczyk, Vladyslav Vivcharenko, Robert Nowakowski, Izabela S. Pieta i Agata Przekora. "Surface Chemical and Morphological Analysis of Chitosan/1,3-β-d-Glucan Polysaccharide Films Cross-Linked at 90 °C". International Journal of Molecular Sciences 23, nr 11 (25.05.2022): 5953. http://dx.doi.org/10.3390/ijms23115953.
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The cross-linking temperature of polymers may affect the surface characteristics and molecular arrangement, which are responsible for their mechanical and physico-chemical properties. The aim of this research was to determine and explain in detail the mechanism of unit interlinkage of two-component chitosan/1,3-β-d-glucan matrices gelled at 90 °C. This required identifying functional groups interacting with each other and assessing surface topography providing material chemical composition. For this purpose, various spectroscopic and microscopic approaches, such as attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), were applied. The results indicate the involvement mainly of the C-C and C-H groups and C=O⋯HN moieties in the process of biomaterial polymerization. Strong chemical interactions and ionocovalent bonds between the N-glucosamine moieties of chitosan and 1,3-β-d-glucan units were demonstrated, which was also reflected in the uniform surface of the sample without segregation. These unique properties, hybrid character and proper cell response may imply the potential application of studied biomaterial as biocompatible scaffolds used in regenerative medicine, especially in bone restoration and/or wound healing.
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Stucchi, Marta, Sofia Capelli, Simone Cardaci, Stefano Cattaneo, Andrea Jouve, Andrea Beck, György Sáfrán, Claudio Evangelisti, Alberto Villa i Laura Prati. "Synergistic Effect in Au-Cu Bimetallic Catalysts for the Valorization of Lignin-Derived Compounds". Catalysts 10, nr 3 (16.03.2020): 332. http://dx.doi.org/10.3390/catal10030332.
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The selective oxidation of veratryl alcohol as lignin-derived compound was studied under mild conditions, using Au-Cu catalysts synthesized from pre-formed nanoparticles with different Au:Cu molar ratios. Bimetallic catalysts show higher activity compared to monometallic counterparts, highlighting a clear synergistic effect. By comparing the physico-chemical surface properties of catalysts supported on carbon and Al2O3, we were able to establish a strong support effect, with alumina-based catalysts being more active than carbon-supported ones. Moreover, TEM and X-ray photoelectron spectroscopy (XPS) analyses showed a different composition of nanoparticles (NPs) and metal exposure, and we established that Au is the active phase of the reaction. The co-presence of Au and Cu species, and their different interaction with the support, enabled obtaining more than 70% conversion of veratryl alcohol to veratryl aldehyde as a unique product. Moreover, the Au1Cu1 supported on alumina catalyst was recovered by filtration and reused without significant loss of activity and selectivity up to four times.
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Yang, Zhenglong, Yan Cui, Pengxiang Ge, Mindong Chen i Leilei Xu. "CO2 Methanation over Rare Earth Doped Ni-Based Mesoporous Ce0.8Zr0.2O2 with Enhanced Low-Temperature Activity". Catalysts 11, nr 4 (1.04.2021): 463. http://dx.doi.org/10.3390/catal11040463.
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The Ni-based catalysts have a wide range of industrial applications due to its low cost, but its activity of CO2 methanation is not comparable to that of precious metal catalysts. In order to solve this problem, Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts doped with rare earth were prepared by the incipient impregnation method and directly used as catalysts for the methanation of CO2. The catalysts were characterized systematically by X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), energy-dispersed spectroscopy (EDS) mapping, X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), and so on. The results show that Ni is highly dispersed in the mesoporous skeleton, forming a strong metal-skeleton interaction. Therefore, under the condition of CO2 methanation, the hot sintering of metallic Ni nanoparticles can be effectively inhibited so that these mesoporous catalysts have good stability without obvious deactivation. The rare earth doping can significantly increase the surface alkalinity of catalyst and enhance the chemisorption of CO2. In addition, the rare earth elements also act as electron modifiers to help activate CO2 molecules. Therefore, the rare earth doped Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts are expected to be an efficient catalyst for the methanation of CO2 at low-temperature.
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Lykaki, Maria, Sofia Stefa, Sόnia Carabineiro, Pavlos Pandis, Vassilis Stathopoulos i Michalis Konsolakis. "Facet-Dependent Reactivity of Fe2O3/CeO2 Nanocomposites: Effect of Ceria Morphology on CO Oxidation". Catalysts 9, nr 4 (19.04.2019): 371. http://dx.doi.org/10.3390/catal9040371.
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Ceria has been widely studied either as catalyst itself or support of various active phases in many catalytic reactions, due to its unique redox and surface properties in conjunction to its lower cost, compared to noble metal-based catalytic systems. The rational design of catalytic materials, through appropriate tailoring of the particles’ shape and size, in order to acquire highly efficient nanocatalysts, is of major significance. Iron is considered to be one of the cheapest transition metals while its interaction with ceria support and their shape-dependent catalytic activity has not been fully investigated. In this work, we report on ceria nanostructures morphological effects (cubes, polyhedra, rods) on the textural, structural, surface, redox properties and, consequently, on the CO oxidation performance of the iron-ceria mixed oxides (Fe2O3/CeO2). A full characterization study involving N2 adsorption at –196 °C, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) was performed. The results clearly revealed the key role of support morphology on the physicochemical properties and the catalytic behavior of the iron-ceria binary system, with the rod-shaped sample exhibiting the highest catalytic performance, both in terms of conversion and specific activity, due to its improved reducibility and oxygen mobility, along with its abundance in Fe2+ species.
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de Longe, Clenildo, Rafael Viana Sales, Anne Beatriz Figueira Câmara, Heloise Oliveira Medeiros de Araújo Moura, Enrique Rodríguez-Castellón, Sibele Berenice Castellã Pergher, Leila Maria Aguilera Campos, Maritza Montoya Urbina i Luciene Santos de Carvalho. "Effective Interactions of Ag Nanoparticles on the Surface of SBA-15 in Performing Deep Desulfurization of Real Diesel Fuel". Catalysts 10, nr 5 (25.05.2020): 593. http://dx.doi.org/10.3390/catal10050593.
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SBA-15 materials as-synthesized and impregnated with Ag nanoparticles were applied to perform adsorptive desulfurization of real diesel fuel. High-angle annular dark-field scanning transmission electron microscopy and field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (HAADF-STEM-EDX and FESEM-EDX) and X-ray photoelectron spectroscopy (XPS) results confirmed that there is uniform distribution of Ag nanodomains on the surface and in the channels of a 2AgSBA-15 (2% Ag) sample. The interaction between sulfur compounds and adsorbent mainly occurred via π-complexation mechanisms, as observed via XPS and equilibrium data. The kinetic results for 2AgSBA-15 were better fitted to the pseudo-second-order model (R2 > 0.9999), indicating that the determining step of the adsorptive process is chemisorption, whereas the equilibrium results were better fitted to the Langmuir model (R2 > 0.9994), thus indicating that the adsorption occurs on the adsorbent surface monolayer with significant adsorption capacity (qm = 20.30 mgS/g), approximately two times greater than that observed for pure SBA-15. The mean desulfurization reached by the adsorbents was up to 86.8% for six recycling steps.
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V. Sales, Rafael, Heloise O. M. A. Moura, Anne B. F. Câmara, Enrique Rodríguez-Castellón, José A. B. Silva, Sibele B. C. Pergher, Leila M. A. Campos, Maritza M. Urbina, Tatiana C. Bicudo i Luciene S. de Carvalho. "Assessment of Ag Nanoparticles Interaction over Low-Cost Mesoporous Silica in Deep Desulfurization of Diesel". Catalysts 9, nr 8 (30.07.2019): 651. http://dx.doi.org/10.3390/catal9080651.
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Chemical interactions between metal particles (Ag or Ni) dispersed in a low-cost MCM-41M produced from beach sand amorphous silica and sulfur compounds were evaluated in the deep adsorptive desulfurization process of real diesel fuel. N2 adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (STEM-EDX) were used for characterizing the adsorbents. HRTEM and XPS confirmed the high dispersion of Ag nanoparticles on the MCM-41 surface, and its chemical interaction with support and sulfur compounds by diverse mechanisms such as π-complexation and oxidation. Thermodynamic tests indicated that the adsorption of sulfur compounds over Ag(I)/MCM-41M is an endothermic process under the studied conditions. The magnitude of ΔH° (42.1 kJ/mol) indicates that chemisorptive mechanisms govern the sulfur removal. The best fit of kinetic and equilibrium data to pseudo-second order (R2 > 0.99) and Langmuir models (R2 > 0.98), respectively, along with the results for intraparticle diffusion and Boyd’s film-diffusion kinetic models, suggest that the chemisorptive interaction between organosulfur compounds and Ag nanosites controls sulfur adsorption, as seen in the XPS results. Its adsorption capacity (qm = 31.25 mgS/g) was 10 times higher than that obtained for pure MCM-41M and double the qm for the Ag(I)/MCM-41C adsorbent from commercial silica. Saturated adsorbents presented a satisfactory regeneration rate after a total of five sulfur adsorption cycles.
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Kiwi, John, i Sami Rtimi. "Mechanisms of the Antibacterial Effects of TiO2–FeOx under Solar or Visible Light: Schottky Barriers versus Surface Plasmon Resonance". Coatings 8, nr 11 (4.11.2018): 391. http://dx.doi.org/10.3390/coatings8110391.
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This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. The interaction between the film active surface species and the bacteria within the disinfection period was followed by X-ray photoelectron spectroscopy (XPS) and provided the evidence for a redox catalysis taking place during the bacterial inactivation time. The optical and surface properties of the films were evaluated by appropriate surface analytical methods. A differential mechanism is suggested for each specific microstructure inducing bacterial inactivation. The surface FeOx plasmon resonance transferred electrons into the conduction band of TiO2 because of the Schottky barrier after Fermi level equilibration of the two components. An electric field at the interface between TiO2 and FeOx, favors the separation of the photo-generated charges leading to a faster bacterial inactivation by TiO2–FeOx compared to the bacterial inactivation kinetics by each of the single oxides.
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Silva, Cristina, Irina Borbáth, Kristóf Zelenka, István E. Sajó, György Sáfrán, András Tompos i Zoltán Pászti. "Effect of the reductive treatment on the state and electrocatalytic behavior of Pt in catalysts supported on Ti0.8Mo0.2O2-C composite". Reaction Kinetics, Mechanisms and Catalysis 135, nr 1 (11.12.2021): 29–47. http://dx.doi.org/10.1007/s11144-021-02131-4.
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AbstractTi(1-x)MoxO2-carbon composites are promising new supports for Pt-based electrocatalysts in polymer electrolyte membrane fuel cells offering exciting catalytic properties and enhanced stability against electrocorrosion. Pt and the mixed oxide form a couple liable for strong metal-support interaction (SMSI) phenomenon, generally manifesting itself in decoration of the metal particles by ultrathin layers of the support material upon annealing under reductive conditions. The aim of this work is to evaluate the SMSI phenomenon as a potential strategy for tailoring the properties of the electrocatalyst. A 20 wt% Pt/50 wt% Ti0.8Mo0.2O2-50 wt% C electrocatalyst prepared on Black Pearls 2000 carbon functionalized with HNO3 and glucose was reduced at 250 °C in H2 in order to induce SMSI. The electrocatalytic properties and the stability of the reduced and the original catalysts were analyzed by cyclic voltammetry and COads stripping voltammetry. Structural investigations as well as X-ray photoelectron spectroscopy (XPS) measurements were performed in order to obtain information about the details of the interaction between the oxide and the Pt particles. The electrochemical experiments pointed out a small loss of the electrochemically active surface area of Pt in the reduced catalyst along with enhanced stability with respect to the original one, while structural studies suggested only a minimal decrease of the Pt dispersion. At the same time, hydrogen exposure experiments combined with XPS demonstrated the presence of Mo species directly adsorbed on the Pt surface. Thus, the properties of the reduced catalyst can be traced to decoration of the surface of Pt by Mo-containing species.
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Islam, Mohammad, Zineb Matouk, Nadir Ouldhamadouche, Jean-Jacques Pireaux i Amine Achour. "Plasma Treatment of Polystyrene Films—Effect on Wettability and Surface Interactions with Au Nanoparticles". Plasma 6, nr 2 (29.05.2023): 322–33. http://dx.doi.org/10.3390/plasma6020022.
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Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed with ammonia (NH3), oxygen (O2), or tetrafluoroethane (C2H2F4). X-Ray photoelectron spectroscopy (XPS) analysis revealed modified surface chemistry for Ar/O2, Ar/NH3, or Ar/C2H2F4 plasma treatment through the incorporation of oxygen, nitrogen, or fluorine groups, respectively. Size-controlled magnetron sputter deposition of Au nanoparticles (NP) onto these plasma-treated PS films was investigated via XPS and AFM techniques. The interaction of the Au NPs, as probed from the XPS and AFM measurements, is discussed by referring to changes in surface chemistry and morphology of the PS after plasma treatment. The results demonstrate the effect of surface chemistry on the interaction of Au NPs with polymer support having different surface functionalities. The XPS results show that significant oxygen surface incorporation resulted from oxygen-containing species in the plasma itself. The surface concentration of O increased from 0.4% for the pristine PS to 4.5 at%, 35.4 at%, and 45.6 at% for the Ar/C2H4F4, Ar/NH3, and Ar/O2, respectively. The water contact angle (WCA) values were noticed to decrease from 98° for the untreated PS to 95°, 37°, and 15° for Ar/C2H2F4, Ar/NH3, and Ar/O2 plasma-modified PS samples, respectively. AFM results demonstrate that surface treatment was also accompanied by surface morphology change. Small Au islands are well dispersed and cover the surface, thus forming a homogeneous, isotropic structure. The reported results are important for exploiting Au NPs use in catalysis and sensing applications.
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ZHAO, XI, YING ZHANG, YANG SONG i GANG WEI. "XPS STUDY OF INTERACTION OF TITANIUM SPECIES WITH DIFFERENT INTERNAL ELECTRON DONORS ON Z–N CATALYSTS". Surface Review and Letters 14, nr 05 (październik 2007): 951–55. http://dx.doi.org/10.1142/s0218625x07010482.
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TiCl 4/ MgCl 2, TiCl 4/ MgCl 2/donor catalysts and TiCl 4/donor complexes were prepared in this experiment; the donors are EB, DNBP, DBPG, DBW, PPDE, and BMMF respectively. Chemical states of Ti on the surface of MgCl 2-supported Z – N catalysts were analyzed with X-ray photoelectron spectroscopy (XPS). The interaction among components of a catalyst is characterized, and the function of internal donor in the catalyst was demonstrated according to the change of binding energy of Ti 2 p 3/2. We may conclude from the experiment that the kind of internal donors influence the electron density around titanium, and further the electron density around active titanium species effect catalyst activity to some extent. It was also noted that the interaction between internal donors and titanium is weakened remarkably by moisture and oxygen in ambient.
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Yu, L. G., E. S. Yamaguchi, M. Kasrai i G. M. Bancroft. "The chemical characterization of tribofilms using XANES — Interaction of nanosize calcium-containing detergents with zinc dialkyldithiophosphate". Canadian Journal of Chemistry 85, nr 10 (1.10.2007): 675–84. http://dx.doi.org/10.1139/v07-045.
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A Plint friction and wear tester was used to investigate the effect of several calcium-containing detergents on the tribological and tribochemical performance of a zinc dialkyldithiophosphate (ZDDP) lubricating oil additive in a low-sulfur base stock, 100N. Thus, the friction and wear behavior of a steel-on-steel contact lubricated by 100N oil containing ZDDP alone and ZDDP–detergent mixtures at 100 °C was evaluated in a pin-on-disc configuration. The wear scar width of the upper steel pins was determined using an optical microscope, while the tribofilms formed on the lower steel discs were analyzed using X-ray absorption near edge structure (XANES) spectroscopy and X-ray photoelectron spectroscopy (XPS). At the same time, the thermal-oxidation films of the oil blends containing different additives were also prepared on the same steel discs and analyzed using XANES spectroscopy for comparative studies. It was found that in simple formulations the three kinds of calcium-containing detergents improved the friction-reducing and antiwear abilities of the 100N base stock. This was related to the individual tribochemical reactions and the deposition (in one case) of nanosized CaCO3 on the rubbing steel surface, indicating that the calcium-containing detergent had a synergistic antiwear performance with the ZDDP tested in the present work. Moreover, the calcium-containing detergents contributed to retarding the thermo-oxidation and friction-induced decomposition of ZDDP in 100N oil and influenced the composition and thickness of the tribofilms, which could be dependent on the molecular structures of the detergents and directly related to the tribochemistry of ZDDPs in mineral oil. The rubbing of the steel–steel pair at 100 °C was more beneficial for the deposition of nanosized calcium carbonate on the steel surface than heating at 150 °C. The calcium-containing detergents alone in the base stock also experienced tribochemical reactions, leading to obvious changes in the oxidation state of S in the corresponding tribofilms. Therefore, it was supposed that the tribochemical reactions of the ZDDP and detergents together with the deposition of nanosized CaCO3 on the rubbing steel surfaces accounted for the good antiwear performance of the blended oils.Key words: ZDDP, detergent, thermal film, tribofilm, tribochemistry, XANES, XPS.
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Charisiou, Nikolaos D., Georgios I. Siakavelas, Victor Sebastian, Steven J. Hinder, Mark A. Baker, Vagelis G. Papadakis, Wen Wang, Kyriaki Polychronopoulou i Maria A. Goula. "Structural Investigation of the Carbon Deposits on Ni/Al2O3 Catalyst Modified by CaO-MgO for the Biogas Dry Reforming Reaction". Chemistry Proceedings 2, nr 1 (9.11.2020): 15. http://dx.doi.org/10.3390/eccs2020-07569.
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Ni catalysts based on Al2O3 and Al2O3 modified with CaO-MgO were tested for the dry reforming of biogas (BDR). Time-on-stream experiments were carried out between 600 and 800 °C, and the spent catalysts were examined using a variety of characterization techniques including, N2 adsorption/desorption, thermogravimetric analysis (TGA), Raman spectroscopy, electron microscopy (STEM-HAADF and HR-TEM), and X-ray photoelectron spectroscopy (XPS). It was revealed that the carbon deposits consisted of carbon nanotubes and amorphous carbon for both samples. XPS studies showed the presence of Ni0 on both catalysts and Ni2O3/NiAl2O4 on the Ni/Al2O3 sample. The time-on-stream experiments showed that the Ni/CaO-MgO-Al2O3 catalyst is more resistant to deactivation and more active and selective for all temperatures under investigation. It was concluded that doping Al2O3 with CaO-MgO enhances catalytic performance as: (a) it helps to maintain highly dispersed Ni0 during the BDR as the interaction between metal and support is a stronger one, (b) it leads to the formation of carbon structures that are easier to oxidize, and (c) it facilitates the gasification of the carbon deposits because its increased surface basic sites enhance the adsorption of carbon dioxide.
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Sadykov, Vladislav A., Mikhail N. Simonov, Natalia V. Mezentseva, Svetlana N. Pavlova, Yulia E. Fedorova, Aleksei S. Bobin, Yulia N. Bespalko i in. "Ni-loaded nanocrystalline ceria-zirconia solid solutions prepared via modified Pechini route as stable to coking catalysts of CH4 dry reforming". Open Chemistry 14, nr 1 (1.01.2016): 363–76. http://dx.doi.org/10.1515/chem-2016-0039.
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AbstractMixed nanocrystalline Ce-Zr-O oxides (Ce/Zr = 1 or 7/3) were prepared by modified Pechini route using ethylene glycol solutions of metal salts. Detailed characterization of their real structure and surface properties by X-ray diffraction on synchrotron radiation with the full-profile Rietveld analysis, high resolution electron microscopy with elemental analysis, Raman spectroscopy, UV-Vis and X-ray photoelectron spectroscopy revealed a high homogeneity of cations distribution in nanodomains resulting in stabilization of disordered cubic phase. This provides a high dispersion of NiO loaded on these mixed oxides by wet impregnation, a high reactivity and mobility of oxygen in these catalysts and strong interaction of Ni with support in the reduced state. This helps to achieve a high activity and coking stability of developed catalysts in CH4 dry reforming in feeds with CH4 concentration up to 15% and CH4/CO2 ratio =1.
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Peck, Torin C., Charles A. Roberts i Gunugunuri K. Reddy. "Contrasting Effects of Potassium Addition on M3O4 (M = Co, Fe, and Mn) Oxides during Direct NO Decomposition Catalysis". Catalysts 10, nr 5 (19.05.2020): 561. http://dx.doi.org/10.3390/catal10050561.
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While the promotional effect of potassium on Co3O4 NO decomposition catalytic performance is established in the literature, it remains unknown if K is also a promoter of NO decomposition over similar simple first-row transition metal spinels like Mn3O4 and Fe3O4. Thus, potassium was impregnated (0.9–3.0 wt.%) on Co3O4, Mn3O4, and Fe3O4 and evaluated for NO decomposition reactivity from 400–650 °C. The activity of Co3O4 was strongly dependent on the amount of potassium present, with a maximum of ~0.18 [(µmol NO to N2) g−1 s−1] at 0.9 wt.% K. Without potassium, Fe3O4 exhibited deactivation with time-on-stream due to a non-catalytic chemical reaction with NO forming α-Fe2O3 (hematite), which is inactive for NO decomposition. Potassium addition led to some stabilization of Fe3O4, however, γ-Fe2O3 (maghemite) and a potassium–iron mixed oxide were also formed, and catalytic activity was only observed at 650 °C and was ~50× lower than 0.9 wt.% K on Co3O4. The addition of K to Mn3O4 led to formation of potassium–manganese mixed oxide phases, which became more prevalent after reaction and were nearly inactive for NO decomposition. Characterization of fresh and spent catalysts by scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), in situ NO adsorption Fourier transform infrared spectroscopy, temperature programmed desorption techniques, X-ray powder diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed the unique potassium promotion of Co3O4 for NO decomposition arises not only from modification of the interaction of the catalyst surface with NOx (increased potassium-nitrite formation), but also from an improved ability to desorb oxygen as product O2 while maintaining the integrity and purity of the spinel phase.
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Wang, Xian-sheng, Yu-duo Zhang, Qiao-chu Wang, Bo Dong, Yan-jia Wang i Wei Feng. "Photocatalytic activity of Cu2O/ZnO nanocomposite for the decomposition of methyl orange under visible light irradiation". Science and Engineering of Composite Materials 26, nr 1 (28.01.2019): 104–13. http://dx.doi.org/10.1515/secm-2018-0170.
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AbstractZnO is modified by Cu2O by the process of precipitation and calcination. X-ray diffraction has shown that Cu2O/ZnO catalysts are made of highly purified cubic Cu2O and hexagonal ZnO. Scanning electron microscopy and transmission electron microscopy have shown that ZnO adhered to the surface of Cu2O. Due to the doping of Cu2O, the absorption range of the Cu2O/ZnO catalyst is shifted from the ultraviolet to the visible region due to diffuse reflection. X-ray photoelectron spectroscopy and photoluminescence spectra have confirmed that there is a substantial interaction between the two phases of the resultant catalyst. The degradation efficiency of Cu2O/ZnO on methyl orange solution is obviously enhanced compared to Cu2O and ZnO. The maximum degradation efficiency is 98%. The degradation efficiency is affected by the pH of the solution and initial concentration. After three rounds of recycling, the degradation rate is almost same. This shows a consistent performance of Cu2O/ZnO. The increase in catalytic ability is related to the lattice interaction caused by the doping of Cu2O.
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Zhang, Yu, Dongdong Feng, Yijun Zhao, Heming Dong, Guozhang Chang, Cui Quan, Shaozeng Sun i Yukun Qin. "Evolution of Char Structure During In-Situ Biomass Tar Reforming: Importance of the Coupling Effect Among the Physical-Chemical Structure of Char-Based Catalysts". Catalysts 9, nr 9 (24.08.2019): 711. http://dx.doi.org/10.3390/catal9090711.
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In order to illustrate the importance of a coupling effect in the physical-chemical structure of char-based catalysts on in-situ biomass tar reforming, three typical char-based catalysts (graphite, Zhundong coal char, and sawdust biochar) were studied in the fixed-bed/fluidized-bed reactor. The physical-chemical properties of carbon-based catalysts associated with their catalytic abilities were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope–energy dispersive spectrometer (SEM-EDS) and N2 adsorption. The relationship between the specific reactivity and tar reforming ability of carbon-based catalysts was discussed through a micro fluidized bed reaction analyzer (MFBRA–MR). The results indicate that the char-based catalyst has a certain removal ability for in-situ biomass tar of corn straw in an inert atmosphere, which is as follows: sawdust biochar > Zhundong (ZD) coal char > graphite. During the in-situ tar reforming, the alkali and alkaline earth metal species (AAEMs) act as adsorption/reaction sites, affecting the evolution of the aromatic ring structure and oxygen-containing functional groups of the char-based catalyst, and also its pore structure. AAEM species on the surface of char-based catalysts are the active sites for tar reforming, which promotes the increase of active intermediates (C-O bond and C-O-AAEMs), and enhances the interactions between char-based catalysts and biomass tar. The abundant AAEMs may lead to the conversion of O=C–O and C=O to C–O. For tar reforming, the internal pore structure of char-based catalysts is little changed, mainly with the carbon deposit forming on the surface pore structure. The carbon deposit from the reformation of straw tar on the char surface has better reactivity than the inherent carbon structure of ZD coal char and sawdust biochar. There is a positive relationship between the MFBRA–MR specific reactivity and tar catalytic reforming ability of char-based catalysts (decided by the coupling effect in their physical-chemical structure), which can be used to determine the catalytic ability of char-based catalysts on tar reforming directly.
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Uhl, Benedikt, Florian Buchner, Stephan Gabler, Maral Bozorgchenani i R. Jürgen Behm. "Adsorption and reaction of sub-monolayer films of an ionic liquid on Cu(111)". Chem. Commun. 50, nr 62 (2014): 8601–4. http://dx.doi.org/10.1039/c4cc03203a.
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The reactive interaction of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSA] with Cu(111) was investigated by scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) under ultrahigh vacuum (UHV) conditions.
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Štěpánková, Kateřina, Kadir Ozaltin, Jana Pelková, Hana Pištěková, Ilkay Karakurt, Simona Káčerová, Marian Lehocky, Petr Humpolicek, Alenka Vesel i Miran Mozetic. "Furcellaran Surface Deposition and Its Potential in Biomedical Applications". International Journal of Molecular Sciences 23, nr 13 (4.07.2022): 7439. http://dx.doi.org/10.3390/ijms23137439.
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Surface coatings of materials by polysaccharide polymers are an acknowledged strategy to modulate interfacial biocompatibility. Polysaccharides from various algal species represent an attractive source of structurally diverse compounds that have found application in the biomedical field. Furcellaran obtained from the red algae Furcellaria lumbricalis is a potential candidate for biomedical applications due to its gelation properties and mechanical strength. In the present study, immobilization of furcellaran onto polyethylene terephthalate surfaces by a multistep approach was studied. In this approach, N-allylmethylamine was grafted onto a functionalized polyethylene terephthalate (PET) surface via air plasma treatment. Furcellaran, as a bioactive agent, was anchored on such substrates. Surface characteristics were measured by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Subsequently, samples were subjected to selected cell interaction assays, such as antibacterial activity, anticoagulant activity, fibroblasts and stem cell cytocompatibility, to investigate the Furcellaran potential in biomedical applications. Based on these results, furcellaran-coated PET films showed significantly improved embryonic stem cell (ESC) proliferation compared to the initial untreated material.
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Farooq, Muhammad, Anita Ramli i Duvvuri Subbarao. "Evaluation of the Physiochemical Properties of Molybdenum Supported Catalysts". Advanced Materials Research 488-489 (marzec 2012): 206–10. http://dx.doi.org/10.4028/www.scientific.net/amr.488-489.206.
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Molybdenum catalysts supported on γ-Al2O3and γ-Al2O3-MgO mixed oxide with varying loading of MgO (5, 10, 15, 20 wt% with respect to γ-Al2O3) were prepared successfully by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied by various analytical techniques such as N2adsorption–desorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature-programmed reduction (TPR).The results showed that the addition of MgO into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.
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Smirnova, Marina Yu, Aleksei S. Bobin, Svetlana N. Pavlova, Arcady V. Ishchenko, Aleksandra V. Selivanova, Vasilii V. Kaichev, Svetlana V. Cherepanova i in. "Methane dry reforming over Ni catalysts supported on Ce–Zr oxides prepared by a route involving supercritical fluids". Open Chemistry 15, nr 1 (29.12.2017): 412–25. http://dx.doi.org/10.1515/chem-2017-0046.
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AbstractCe0.5Zr0.5O2mixed oxides were prepared in a flow reactor in supercritical isopropanol with acetylacetone as a complexing agent. Variation of the nature of the Zr salt and the temperature of synthesis affected the phase composition, morphology and specific surface area of oxides. X-ray diffraction and Raman spectroscopy studies revealed formation of metastable t” and t’ phases. Oxides are comprised of agglomerates with sizes depending on the synthesis parameters. Loading NiO decreases the specific surface area without affecting X-ray particle sizes of supports. Such sintering was the most pronounced for a support with the highest specific surface area, which resulted in the lowest surface content of Ni as estimated by X-ray photoelectron spectroscopy and in the formation of flattened NiO particles partially embedded into the support. The catalytic activity and stability of these samples in the dry reforming of methane were determined by the surface concentration of Ni and the morphology of its particle controlled by the metal-support interaction, which also depends on the type of catalyst pretreatment. Samples based on ceria-zirconia oxides prepared under these conditions provide a higher specific catalytic activity as compared with the traditional Pechini route, which makes them promising for the practical application.
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Ometto, Felipe Berto, Valdecir Antonio Paganin, Peter Hammer i Edson Antonio Ticianelli. "Effects of Metal–Support Interaction in the Electrocatalysis of the Hydrogen Evolution Reaction of the Metal-Decorated Titanium Dioxide Supported Carbon". Catalysts 13, nr 1 (23.12.2022): 22. http://dx.doi.org/10.3390/catal13010022.
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It has been found that the electrocatalytic properties of metallic nanoparticles supported on transition metal oxides are affected by the existing strong metal–support interaction (SMSI). Herein, the effects of SMSI on the electrocatalysis of the hydrogen evolution reaction (HER) were investigated in acid electrolyte by using Pt and Ag nanoparticles supported on carbon and titanium oxide (TiO2). High-resolution transmission electron microscopy (HR–TEM) images showed that Pt and Ag nanoparticles present a spherical shape at the TiO2 support and an average size distribution of around 4.5 nm. The X-ray photoelectron spectroscopy (XPS) results for Pt/TiO2/C and Ag/TiO2/C evidenced higher amounts of surface oxides in the metallic particles, when compared to the materials supported on carbon. Consistently, electrode polarization and electrochemical impedance results revealed that both metal–TiO2 and metal–C-supported catalysts were more active in catalyzing the HER than the corresponding carbon-supported materials, with Pt presenting better results. These differences in the HER activities were related to the electronic effects of the TiO2/C substrate on the Pt and Ag metals, introduced by strong metal-support (SMSI) in the metal–TiO2/C catalysts.
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Yano, Junko, Xiang Li, Corey Kaminsky, Dimosthenis Sokaras i Ethan J. Crumlin. "(Invited, Digital Presentation) Application of in Situ X-Ray Spectroscopy Techniques for Studying CO2 Reduction Reaction". ECS Meeting Abstracts MA2022-02, nr 48 (9.10.2022): 1833. http://dx.doi.org/10.1149/ma2022-02481833mtgabs.
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Artificial photosynthesis capable of the CO2 reduction reaction (CO2RR), with solar energy as external excitation energy and water (H2O) as the electron and proton source, has been considered an attractive method to achieve a sustainable energy cycle, since it allows direct solar-to-chemical energy conversion. To design such systems, X-ray techniques play an important role for gaining the fundamental understanding needed to tailor its components and assemblies, by providing their chemical and structural information [1-3]. We have utilized surface-sensitive soft and hard X-ray techniques to investigate the interaction of metal catalytic surfaces with electrolytes and/or gases (H2O and/or CO2) under in situ/operando conditions. Among those, Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) probes CO2 adsorption on catalyst surfaces, providing the information of the initial atomic level events for CO2 electroreduction on the metal catalysts. In situ X-ray absorption spectroscopy, on the other hand, can complement the study by providing metal catalytic surface sensitive information. We discuss in situ studies of the CO2 reduction reaction, with Cu and related oxides and alloys. Reference [1] Lee, S.H.; Lin, J.C.; Farmand, M.; Landers, A.T.; Feaster, J.T.; Avilés Acosta, J.E.; Beeman, J.W.; Ye, Y.; Yano, J.; Mehta, A.; Davis, R.C.; Jaramillo, T.F.; Hahn, C.; Drisdell, W.S., J. Am. Chem. Soc. 143, 588–592 (2020). [2] Ye, Y.; Su, J.; Lee, K.-J.; Larson, D.; Valero-Vidal, C.; Blum, M.; Yano, J.; Crumlin, E.J., J. Phys. D: Appl. Phys. 54, 234002 (2021). [3] Ye, Y.; Qian, J.; Yang, H.; Su, H.; Lee, K. -J.; Etxebarria, A.; Cheng, T.; Xiao, H.; Yano, J.; Goddard, W. A.; Crumlin, E. J., ACS Appl. Mater. Interfaces, 12, 25374–25382 (2020).
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Awang, Huzaikha, Tim Peppel i Jennifer Strunk. "Photocatalytic Degradation of Diclofenac by Nitrogen-Doped Carbon Quantum Dot-Graphitic Carbon Nitride (CNQD)". Catalysts 13, nr 4 (13.04.2023): 735. http://dx.doi.org/10.3390/catal13040735.
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In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C3N4 (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10−3 min−1. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O2−) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater.
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Kim, Nagyeong, Seulgi Lim, Seungdon Kwon, Yuyeol Choi, Ji-Woong Lee i Kyungsu Na. "Controlled Metal–Support Interactions in Au/CeO2–Mg(OH)2 Catalysts Activating the Direct Oxidative Esterification of Methacrolein with Methanol to Methyl Methacrylate". Nanomaterials 11, nr 11 (21.11.2021): 3146. http://dx.doi.org/10.3390/nano11113146.
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The strong metal–support interaction (SMSI) between the three components in Au/CeO2–Mg(OH)2 can be controlled by the relative composition of CeO2 and Mg(OH)2 and by the calcination temperature for the direct oxidative esterification of methacrolein (MACR) with methanol to methyl methacrylate (MMA). The composition ratio of CeO2 and Mg(OH)2 in the catalyst affects the catalytic performance dramatically. An Au/CeO2 catalyst without Mg(OH)2 esterified MACR to a hemiacetal species without MMA production, which confirmed that Mg(OH)2 is a prerequisite for successful oxidative esterification. When Au/Mg(OH)2 was used without CeO2, the direct oxidative esterification of MACR was successful and produced MMA, the desired product. However, the MMA selectivity was much lower (72.5%) than that with Au/CeO2–Mg(OH)2 catalysts, which have an MMA selectivity of 93.9–99.8%, depending on the relative composition of CeO2 and Mg(OH)2. In addition, depending on the calcination temperature, the crystallinity of the CeO2–Mg(OH)2 and the surface acidity/basicity can be remarkably changed. Consequently, the Au-nanoparticle-supported catalysts exhibited different MACR conversions and MMA selectivities. The catalytic behavior can be explained by the different metal–support interactions between the three components depending on the composition ratio of CeO2 and Mg(OH)2 and the calcination temperature. These differences were evidenced by X-ray diffraction, X-ray photoelectron spectroscopy, and CO2 temperature-programmed desorption. The present study provides new insights into the design of SMSI-induced supported metal catalysts for the development of multifunctional heterogeneous catalysts.
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Deng, Zhiping, David C. Stone i Michael Thompson. "Poly N-(2-cyanoethyl)pyrrole as a selective film for the thickness-shear-mode acoustic wave sensor". Canadian Journal of Chemistry 73, nr 9 (1.09.1995): 1427–35. http://dx.doi.org/10.1139/v95-177.
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Poly N-(2-cyanoethyl)pyrrole films have been synthesized by electrochemical polymerization and characterized by cyclic voltammetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Polymeric coatings prepared on the surface of a thickness-shear-mode acoustic wave sensor have been used to examine response selectivity to a number of gas-phase probe molecules. The responses of the poly N-(2-cyanoethyl)pyrrole based sensor are compared with the parent polypyrrole device and rationalized in terms of the molecular interactions between probes and polymer films. The polar cyano functionality enhances interactions with analytes such as acetonitrile. Keywords: gas sensor, thickness-shear-mode acoustic wave sensor, poly N-(2-cyanoethyl)pyrrole film, polypyrrole film, conducting polymer.