出版者・発行元：Journal of Materials Chemistry A  

Oxide perovskites, such as SrCoO3, are considered to be promising air electrode catalysts for solid oxide cells. SrCoO3 is composed of non-precious elements and possesses catalytic activity for various reactions, including an oxygen reduction and an oxygen evolution reaction. However, the catalytic activity of this material is typically limited at reduced temperatures. In this study, the catalytic activity of SrCoO3 was improved by co-doping of cerium (Ce) and samarium (Sm) at the A site (Sr site) of SrCoO3. Although Ce was considered the B-site dopant in terms of ionic size and coordination number, a small amount of Ce was successfully substituted at the Sr site, simultaneously with Sm. Oxygen reduction and evolution activity were significantly increased by substitution of a small amount of cerium (∼2.5 mol%) at the A-site. At 973 K, the maximum power density generated from the LaGaO3-supported cell with Ce-Sm co-doped SrCoO3 as an air electrode was 0.62 W cm−2 in fuel cell mode, and the current density in steam electrolysis mode at 1.5 V was 0.93 A cm−2. The increased air electrode activity could be assigned to the improvement in the surface active sites and electrical conductivity of SrCoO3 by simultaneous substitution of Ce with Sm at the A site.

DOI： 10.1039/d4ta08181a

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出版者・発行元：Applied Catalysis B: Environmental  

Designing a highly efficient fuel electrode for CO2/H2O co-electrolysis with controllable CO/H2 ratios is fundamentally challenging due to the significant influence of water-gas shift (WGS) reaction. Perovskite oxide La0.6Sr0.4Fe0.8Mn0.2O3 (LSFM) has been identified as a promising alternative to conventional Ni-based cermet electrodes, offering inherent redox stability. In this study, LSFM exhibits efficient electrocatalytic activity and remarkable syngas control, with ratios directly controlled by adjusting the CO2/H2O feed. In-situ/ex-situ catalytic analyses reveal LSFM's efficacy in controlling syngas, attributed to substantial CO2 adsorption on its surface. The carbonated surface interacting with H2O leads to the formation of bicarbonate species, acting potential active intermediates that facilitate CO2 electroreduction to CO while suppressing the WGS reaction. Stable syngas control is confirmed by long-term reversible operations at various applied currents with nearly 100 % Faradaic efficiency. This study highlights the great potential of LSFM perovskite for efficient and steady syngas production in co-electrolysis, providing insights into advanced fuel electrode design.

DOI： 10.1016/j.apcatb.2024.124335

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出版者・発行元：Advanced Energy Materials  

The versatility of the spinel (AB2O4) oxides means they are of great interest for a variety of catalysis and energy conversion applications, involving gas reactions and reforming. CuFe2O4 spinel is identified as a highly efficient fuel electrode for CO2/H2O co-electrolysis due to its promising electrocatalytic activity. To identify the actual active sites, the electrochemical characteristics, composition, chemical state, and microstructure are systematically investigated while optimizing the electrolysis performance by varying the feed gas composition. Markedly enhanced electrolysis current density is achieved under a CO2-enriched composition of 50%CO2/10%H2O-Ar. This promising performance is attributed to the in situ exsolution of heterostructural “Cu/Fe3O4” nanoparticles on the parent CuFe2O4 surface during co-electrolysis. Interestingly, a strong correlation of the electrolysis performance with the amount of the formed heterostructural cermet is observed. The exsolved cermet heterostructure plays a crucial role in CO2/H2O electroreduction, as also confirmed by density-functional-theory studies. The self-exsolved Cu/Fe3O4 nanoparticles present exceptional strength due to a strong interaction between the formed metallic Cu and Fe3O4, enabling the electrode to remain active and stable under such high electrical polarization. The excellent durability and stability of the self-exsolved heterostructural nanoparticles are clearly confirmed by long-term operation at high-working voltage with an outstanding Faradaic efficiency (nearly 100%).

DOI： 10.1002/aenm.202301042

Web of Science

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