Carbon support surface effects in the catalytic performance of Ba-promoted Ru catalyst for ammonia synthesis

Carbon-supported Ru catalyst is arguably the most promising applications of Ru catalysts in ammonia synthesis. However, the insufficient stability of Ru/C catalyst greatly limits its applications, and the elimination of surface oxygen species by carbon preactivation has been imagined to be an efficient method for preparing Ru/C catalyst with high stability. However, herein we demonstrate that the presence of some oxygen functional groups in carbon support of Ba-promoted Ru/C catalyst was beneficial not only to the dispersion of Ru particles, but also to the low-temperature hydrogen adsorption. Furthermore, the formation of CO during heat treatment, which was closely related to oxygen groups, enhanced the ammonia synthesis activities of carbon-supported Ru catalyst with Ba promoter. Therefore, Ru catalyst supported on carbon with a large number of surface oxygen groups showed higher activity. Understanding the effect of carbon support surface on the activity and stability of Ru/C provides a basis for the rational design of the optimal carbon-supported metal catalyst for ammonia synthesis and related reactions.