Activity enhancement of ceria-supported Co-Mo bimetallic catalysts by tuning reducibility and metal enrichment

The development of efficient oxides-supported bimetallic catalysts is critical for ammonia synthesis or other catalytic reactions. Herein, the design of ceria-supported Co-Mo bimetallic catalysts with different properties is performed by changing Mo addition to enhance the ammonia synthesis activities. It is found that the reduction of ceria and molybdenum oxide would be boosted by Co species, but the reduction of the bimetallic catalyst would be inhibited by the aggregated molybdenum oxide for the catalyst with Co and Mo simultaneous addition. On the contrary, this ill effect of molybdenum oxide on the reduction of the bimetallic catalyst can be effectively alleviated by the subsequent addition of Mo species to ceria-supported Co catalyst, resulting in enhancement of the proportion of Co metal, Ce3+ and low-valent Mo species, as well as surface enrichment of Co species. In such cases, the amount of the adsorbed hydro-gen and nitrogen species would increase, and hydrogen species preferentially desorbs following a path-way of H-2 formation. As a result, the catalyst obtained by the separate addition of Co and Mo shows 2.5-fold more active than its counterpart with the simultaneous addition of Co and Mo species. These findings provide a valuable insight in designing reducible oxide-supported bimetallic catalysts in ammonia syn-thesis or other hydrogen-involved reactions. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

The development of efficient oxide-supported bimetallic catalysts is crucial for ammonia synthesis or other hydrogen-involved reactions. In this study, ceria-supported Co-Mo bimetallic catalysts with different properties were designed by changing the addition of Mo, resulting in enhanced ammonia synthesis activities. It was found that the negative effect of molybdenum oxide on the reduction of the bimetallic catalyst could be effectively alleviated by the subsequent addition of Mo species, leading to improved catalyst activity.