Inducing the Metal–Support Interaction and Enhancing the Ammonia Synthesis Activity of Ceria-Supported Ruthenium Catalyst via N2H4 Reduction

Metal–support interactions, which are related to electronic metal–support interaction (EMSI), particle morphology, interfacial perimeter, and strong metal–support interaction (SMSI), have a strong impact on the catalytic performance for ceria-supported metal catalysts. High-temperature hydrogen reduction can induce strong metal–support interaction in the Ru/CeO 2 catalyst. However, this treatment under severe conditions would lead to the lowering of metallic Ru species because some Ru metal would be covered by Ce suboxides, which is detrimental to the activity of ammonia synthesis that required metallic Ru as active species. Herein, the Ru/CeO 2 catalyst was obtained by N 2 H 4 treatment under mild conditions to induce a metal–support interaction between Ru and ceria. The result shows that N 2 H 4 reduction not only results in an enhancement of the electronic metal–support interaction but also causes an increase in the fraction of metallic Ru and the amount of the exposed Ru species. Therefore, a larger amount as well as a lower adsorption strength of H 2 would adsorb on the Ru catalyst. As a result, the Ru/CeO 2 catalyst with the N 2 H 4 treatment exhibits a relatively higher ammonia synthesis activity. This discovery offers an effective way for the design of ceria-supported metal catalyst by tuning the interaction between metal and ceria.