Unraveling the role of active site Rh aggregation form in tuning the catalytic performance of ethane direct dehydrogenation

Abstract

Ethane direct dehydrogenation (EDH) is of great importance for shale gas utilization. However, the development of highly active and stable catalyst is still challenge in this process. Here, to guide the establishment of a desired Rh-based catalyst for EDH to ethylene, fifteen catalysts RhxM (M=Cu, Ag, Au) (x=1, 2, 3, 6, 9) are designed and their catalytic performance for EDH are systematically studied by using density functional theory calculations. The computational results disclose that the aggregation form of active Rh atoms (ensemble effect) dominates the catalytic performance, rather than the d-band center, electron transfer and the effects of the second metal substrate. The catalysts Rh1Cu, Rh1Au, and Rh2Ag show the best catalytic performance among the catalysts with different metal substrate. Typically, the low-cost catalyst Rh1Cu with surface single-atom Rh in the non-noble metal Cu not only performs improved activity and selectivity for forming ethylene but also resists the coking. Interestingly, the catalyst Rh3M (M=Cu, Ag, Au) has poor C2H4 selectivity and coking resistance due to itself ensemble effect. This study gives a theoretical guidance for regulating the catalytic performance through the ensemble effect of active site metal atoms in ethane direct dehydrogenation.