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We prepared a highly active and stable cathode catalyst for a solid oxide electrolysis cell (SOEC), decorated with in situ exsolved Fe nanoparticles (NPs) socketed on La1.2Sr0.8Mn0.4Fe0.6O4−α (R.P.LSMF), toward the CO2 electrolysis reaction to produce CO selectively. This catalyst was derived from the perovskite structure of La0.6Sr0.4Mn0.2Fe0.8O3−δ (LSMF) by simple annealing in a H2 atmosphere and showed high current densities of 2.04, 1.43, and 0.884 A cm−2 at 850, 800, and 750 °C, respectively, at a voltage of 1.5 V with corresponding total polarization resistance values of 0.205, 0.326, and 0.587 Ω cm2, respectively, at an open circuit voltage. The highly improved performance should be ascribed to the in situ exsolved Fe NPs anchored on Ruddlesden–Popper oxide and to the increased contents of oxygen vacancies in R.P.LSMF. More importantly, this active catalyst also exhibited a stable voltage profile for 100 h operation at an constant current density of 1.8 A cm−2, suggesting that the catalyst Fe–R.P.LSMF proposed in this study is a highly promising candidate for use in an efficient SOEC cathode for CO2 electrolysis processes.

The application of electrocatalysts with high activity to a practical water electrolysis cell is a crucial challenge for the production of pure hydrogen and commercialization of the water electrolyzer. Herein, a nanosized Cu0.5Co2.5O4 catalyst synthesized by co-precipitation by adjusting pH is applied to the anion exchange membrane water electrolysis (AEMWE) cell as an anode, which is demonstrated to have higher efficiency and stability than noble metal-based anodes. The composition (Cu/Co) and morphology of Cu0.5Co2.5O4 change as the pH increases and then nanoparticles are formed at pH 11, where oxygen vacancies are formed by the etching of Cu. In the density functional theory study, the electronic structure of Co modified by Cu in the Co3O4 lattice leads to an optimal adsorption strength, resulting in a free energy diagram in which the potential of Cu0.5Co2.5O4 (1.756 V vs. reversible hydrogen electrode, RHE) is more thermodynamically favorable than that of Co3O4 (1.951 V vs. RHE). The Cu0.5Co2.5O4 catalyst has a recorded overpotential of 285 mV at 10 mA cm−2 in 1 M KOH. Furthermore, the AEMWE cell using Cu0.5Co2.5O4 as an anode exhibited a current density of 1.3 A cm−2 at 1.8 V, which is the highest performance among the reported papers and maintains around 80% energy conversion efficiency for 100 hours.

We developed a new and efficient sulfur-tolerant catalyst for application as a solid oxide electrolysis cell (SOEC) cathode designed with in situ exsolved CoNi alloy nanoparticles anchored on a Ruddlesden–Popper (R.P.) support of La1.2Sr0.8Co0.4Mn0.6O4 and evaluated its catalytic activity for CO2 electrolysis to CO under a CO2 gas stream containing H2S species. This catalyst was prepared by in situ annealing of a perovskite derivative (La0.6Sr0.4Co0.5Ni0.2Mn0.3O3) in a 20% H2/N2 gas at 800 °C. The catalyst exhibited good reversibility of structural transitions during reduction and re-oxidation processes. A high current density of 703 mA cm−2 was achieved at 1.3 V and 850 °C with a maximum faradaic efficiency of 97.8%. In situ grown CoNi alloy nanoparticles and the high oxygen vacancy content in the R.P. support were responsible for its high catalytic activity and efficiency. Importantly, no sign of performance degradation was observed in galvanostatic tests over a period of 90 h operation under H2S-containing CO2 gas conditions. Moreover, the catalyst showed no noticeable structural changes even after exposure to 100 ppm H2S/N2, indicating that the catalyst developed in this study is highly active for CO2 electrolysis with a high tolerance against sulfur-poisoning species. Therefore, this Ruddlesden–Popper material with in situ exsolved CoNi alloy nanoparticles should be a promising cathode catalyst for practical application to H2S-containing CO2 gas streams that are effluents of power stations or steel making plants.

A highly stable electrode material of Ruddlesden–Popper structure, La1.2Sr0.8Mn0.4Fe0.6O4 (RPLSMF), is prepared from La0.6Sr0.4Mn0.2Fe0.8O3 (LSMF) perovskite by in situ annealing in flowing H2 at the operation temperature of solid oxide fuel cells. The crystallinity, morphology, and oxidation states of each element and electrochemical properties of RPLSMF are characterized. Doping Mn into the B-site of RPLSMF improves the phase stability of the structure in H2 to prevent formation of La2O3. The XPS results also suggest that improved phase stability promotes formation of Fe2+/3+ pairs that facilitate fuel oxidation by redox coupling. Additionally, during phase transition to RPLSMF, metallic Fe nanoparticles form, which enlarge H2 chemisorption and oxidation sites. Consequently, RPLSMF exhibits outstanding and stable electrochemical activity with a maximum power density of 0.72 W cm−2 at 1073 K when used as an anode material in LSGM electrolyte-supported cells. As the phase transition between the RPLSMF and LSMF is reversible under a redox environment, RPLSMF/GDC is applied as an electrode in the symmetrical cell of RPLSMF-GDC/LSGM/LSMF-GDC. It exhibits a substantial power density of 0.64 W cm−2 with a total polarization resistance of 0.51 Ω cm2.