Mechanism-Driven Size Optimization of Fully Exposed Rh Cluster Catalysts for Butane Dehydrogenation

Nonoxidative butane dehydrogenation offers a direct route to C4 olefins, yet it remains challenged by the need to promote C–H activation while ensuring olefin desorption and suppressing C–C cracking. Here, we report a mechanism-guided study that combines density functional theory calculations with experimental validation to rationally design Rh-based catalysts for butane dehydrogenation. A series of Rh models with distinct geometric configurations on a graphene surface, including isolated Rh atom, fully exposed Rh2 and Rh3 clusters, and extended Rh surfaces, were constructed to elucidate the structure–activity relationship. The calculations reveal a volcano-type dependence of dehydrogenation activity on the Rh geometric configuration. Fully exposed Rh3 clusters exhibit optimal energetics for sequential C–H activation, whereas isolated Rh atoms and Rh nanoparticles show inferior activity. Experimental studies on Rh/nanodiamond@graphene catalysts confirm the prediction, demonstrating that fully exposed Rh clusters with an average Rh–Rh coordination number of approximately 1.9 achieve the best balance between C–H activation, olefin desorption, and C–C bond cleavage suppression. This study highlights highly efficient Rh active sites by regulating the geometric configuration and electronic property and provides a general strategy for designing dehydrogenation catalysts.