Role of Perovskite Phase in CeXO3 (X = Ni, Co, Fe) Catalysts for Low-Temperature Hydrogen Production from Ammonia

The drive to utilize ammonia as a carbon-free hydrogen source necessitates the development of effective, non-precious metal catalysts for ammonia decomposition. We successfully synthesized a series of Ce-based perovskite oxides (CeXO3; X = Co, Ni, Fe) via combustion method using citric acid. These catalyst precursors were tested for NH3 decomposition to study the effect of the perovskite structure on catalytic activity. The results were directly compared to corresponding impregnated catalysts, X/CeO2, which had similar metal concentrations. A remarkable enhancement in catalytic performance was observed with the perovskite catalysts, particularly at lower temperatures, relative to their impregnated counterparts. The exception was the CeFeO3 catalyst, which exhibited lower activity, likely due to the formation of metal nitrides. Both CeNiO3 and CeCoO3 showed good NH3 decomposition activity, but CeNiO3 emerged as the most active catalyst at lower temperatures. This superior performance attributed to the presence of oxygen vacancies—confirmed by Raman and XPS analyses—and enhanced metal reducibility at lower temperatures, both of which accelerate NH3 decomposition. Furthermore, CeNiO3 also displayed a high surface metal concentration. These Ce-based perovskite materials are cost-effective, easily synthesized, and highly stable; hence, they are attractive candidates for large-scale hydrogen production.