Enhanced Ammonia Synthesis Activity of Ceria-Supported Ruthenium Catalysts Induced by CO Activation

Metal-support interactions strongly affect the catalytic performances of ceria-supported metal catalysts, and hydrogen treatment at high temperature is important for the preparation of catalysts that show strong metal-support interaction (SMSI). With SMSI, the proportion of metal species existing in the form of a metallic state is lowered, consequently hindering the performance of a metal catalyst for a reaction that requires metallic sites. Here we show that CO activation of a Ru/CeO2 catalyst not only enhances the reduction degree and exposure of Ru species but also increases Ce2+ concentration, oxygen vacancy (O-V), and active oxygen, resulting in the formation of electron-enriched Ru delta- species and Ru delta-OV-Ce3+ sites. As a result, a Ru/CeO2 catalyst after CO activation shows high ammonia synthesis activity, and the ill effect of hydrogen poisoning is effectively alleviated. These findings are important for the design of supported metal catalysts that afford metallic species as active sites.

Automated summary

Metal-support interactions strongly impact the catalytic performances of ceria-supported metal catalysts, and hydrogen treatment at high temperature is essential for the preparation of catalysts with strong metal-support interaction (SMSI). CO activation of a Ru/CeO2 catalyst enhances the reduction degree and exposure of Ru species, leading to the formation of electron-enriched Ru delta- species and Ru delta-OV-Ce3+ sites, resulting in high ammonia synthesis activity and alleviating the ill effect of hydrogen poisoning. These findings are crucial for designing supported metal catalysts with metallic species as active sites.