A sulfur-tolerant cathode catalyst fabricated with in situ exsolved CoNi alloy nanoparticles anchored on a Ruddlesden–Popper support for CO2 electrolysis

Abstract

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 La_1.2Sr_0.8Co_0.4Mn_0.6O₄ 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 (La_0.6Sr_0.4Co_0.5Ni_0.2Mn_0.3O₃) 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.