Highly Active and Stable Ni/La-Doped Ceria Material for Catalytic CO2Reduction by Reverse Water-Gas Shift Reaction

[EN] The design of an active, effective, and economically viable catalyst for CO2 conversion into value-added products is crucial in the fight against global warming and energy demand. We have developed very efficient catalysts for reverse water-gas shift (rWGS) reaction. Specific conditions of the synthesis by combustion allow the obtention of macroporous materials based on nanosized Ni particles supported on a mixed oxide of high purity and crystallinity. Here, we show that Ni/La-doped CeO2 catalysts─with the "right"Ni and La proportions─have an unprecedented catalytic performance per unit mass of catalyst for the rWGS reaction as the first step toward CO2 valorization. Correlations between physicochemical properties and catalytic activity, obtained using a combination of different techniques such as X-ray and neutron powder diffraction, Raman spectroscopy, in situ near ambient pressure X-ray photoelectron spectroscopy, electron microscopy, and catalytic testing, point out to optimum values for the Ni loading and the La proportion. Density functional theory calculations of elementary steps of the reaction on model Ni/ceria catalysts aid toward the microscopic understanding of the nature of the active sites. This finding offers a fundamental basis for developing economical catalysts that can be effectively used for CO2 reduction with hydrogen. A catalyst based on Ni0.07/(Ce0.9La0.1Ox)0.93 shows a CO production of 58 × 10-5 molCO·gcat-1·s-1 (700 °C, H2/CO2 = 2; selectivity to CO > 99.5), being stable for 100 h under continuous reaction.We acknowledge the financial support of the Spanish Ministry of Science and Innovation (PID2021-123287OB-I00, PID2021-122477-OB-I00, PID2021-128915NB-I00, and RTI2018-101604-B-I00) and of the CSIC through the i-LINK 2021 program (LINKA20408). Financial support has also been received from AEI-MINECO/FEDER (Nympha Project, PID2019-106315RB-I00), “Comunidad de Madrid” regional government, and the European Structural Funds (FotoArt-CM project, S2018/NMT-4367). Authors also acknowledge financial support from the grant PLEC2021-007906 funded by MCIN/AEI/10.13039/501100011033 and the “European Union NextGenerationEU/PRTR”. We are grateful to ILL (France) for making all facilities available. This project also received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 832121. Computer time provided by the RES (Red Española de Supercomputación) resources at the MareNostrum 4 (BSC, Barcelona) node and the DECI resources at the BEM cluster of the WCSS based in Poland with the support from PRACE aislb is acknowledged

Composites basados en carbono dopado con nitrógeno y metales no preciosos como electrocatalizadores para pilas de combustible regenerativas en una unidad

Comunicación presentada en la Reunión Bienal de la Sociedad Española de Catálisis - SECAT 2021, celebrada en Valencia, del 18 al 20 de octubre 2021.En los últimos años, las energías renovables han cobrado un papel esencial en el desarrollo tecnológico para satisfacer la demanda energética creciente y sustituir a los combustibles fósiles. Al mismo tiempo, han surgido nuevos retos para poder implementar estas vías de obtención de energía limpia, la incógnita de cómo almacenar a largo plazo la energía renovable que se obtiene de manera intermitente ha favorecido el desarrollo de pilas de combustible, electrolizadores o pilas regenerativas en una unidad (URFC) para utilizar el hidrógeno como un vector energético. Estas últimas se pueden utilizar tanto para la producción de energía eléctrica como para la generación de hidrógeno adaptándose a las necesidades energéticas de la red eléctrica. Los estudios más recientes utilizando una membrana de intercambio aniónico como electrolito, han abierto un abanico de posibilidades a la hora de sintetizar nuevos catalizadores sustituyendo los metales nobles, como el Pt, Ir o Ru, por otros metales de transición más baratos combinándolos con materiales de carbono, como nanotubos o grafeno, óxidos metálicos o estructuras organometálicas (MOFs). Este trabajo se centra en el desarrollo de electrocatalizadores bifuncionales libres de metales nobles, para el electrodo de oxígeno de una URFC alcalina, donde tienen lugar las reacciones de evolución (OER) y reducción (ORR) de oxígeno, las cuales poseen una cinética de reacción lenta. Se han preparado composites basados en metales no preciosos de Co, Fe, Mn, Ni y Zn y nanoestructuras carbonosas dopadas con nitrógeno, obtenidas a partir de precursores poliméricos.Este trabajo ha sido financiado por el Ministerio de Ciencia, Innovación y Universidades (MCIU) y FEDER a través del proyecto HIBRIPEM ENE2017-83976-C2-1-R. J.C. agradece además al Ministerio la concesión de sus contratos FPI.Peer reviewe

Layer Shape LiFePO4 Obtained by Powder Extrusion Molding as Solid Boosters for Ferro/Ferricyanide Catholyte in Semisolid Redox Flow Battery: Effect of Porosity and Shape

[EN] Powder extrusion molding is proposed to fabricate ceramic LiFePO layers (0.5–1.0 mm thickness) as solid booster for ferricyanide electrolyte in semisolid redox flow battery. In some extruded layers, the binder is partially decomposed, while in others it is completely removed and, afterwards, the material is sintered, so materials with different porosity and dimensions are obtained. After characterizing the materials, the kinetics for the reaction with ferricyanide is evaluated, being the binder-less materials the ones which react faster and reach larger degrees of oxidation. For the material with 1.0 mm thick comparable results to the ones already published are obtained (69 % capacity for LiFePO compared to the theoretical value). In the case of the 0.5 mm thick sintered solid, an outstanding performance is achieved, reaching almost the theoretical capacity (94 %) with a very high coulombic efficiency (>99 %) at 1 mA cm, results that were only obtained at much lower current densities in previous works.CONEX-Plus programme funded by Universidad CarlosIII de Madrid and the European Union’s Horizon 2020 research and innovation programme under the MarieSklodowska-Curie grant agreement No. 801538.The authors also thank the Agencia Española de Investigación/Fondo Europeo de Desarrollo Regional(FEDER/UE)for funding the project PID2019-106662RB-C43.This work has also beensupported by Comunidad de Madrid(Spain) though two project:multi annual agreement with UC3M (“Excelencia para el ProfesoradoUniversitario”– EPUC3M04)– Fifth regional research plan 2016–2020,and DROMADER-CM(Y2020/NMT6584