Elucidating the effect of Ce with abundant surface oxygen vacancies on MgAl₂O₄-supported Ru-based catalysts for ammonia decomposition

Ammonia is a promising COx-free hydrogen (H-2) carrier because of its high volumetric H-2 density. However, developing highly active/stable ammonia decomposition catalysts for H-2 production remains challenging. In this study, the role of ceria (CeO2) as a promoter for Ru-based catalysts was investigated. Ru/Ce-x/MgAl(y00) catalysts were prepared by the incipient wetness impregnation (IWP) and deposition-precipitation (DP) methods. The surface oxygen vacancy (OV) concentration was controlled by the Ce loading and calcination temperature. By evaluating the surface reaction behavior of the ammonia decomposition catalysts, this study proposes that CeO2 effectively improves the recombination/desorption of N and H atoms. The optimal catalyst Ru/Ce-5/MgAl(600) achieved a high H-2 formation rate (27.4 mmolH(2).g(cat)(-1).min(-1) at 30,000 mL.g(cat)(-1).h(-1), 450 degrees C) and stable performance after exposure at 650 degrees C for 20 h. This study provides insight into the effect of abundant surface OVs in CeO2 on the physicochemical properties and ammonia decomposition performance of the catalysts.