Adsorption, activation, and conversion of carbon dioxide on small copper-tin nanoclusters.

Carbon dioxide (CO) conversion to value-added chemicals is an attractive solution to reduce globally accelerating CO emissions. Among the non-precious and abundant metals tested so far, copper (Cu) is one of the best electrocatalysts to convert CO into more than thirty different hydrocarbons and alcohols. However, the selectivity for desired products is often too low. We present a computational investigation of the effects of nanostructuring, doping, and support on the activity and selectivity of Cu-Sn catalysts. Density functional theory calculations were conducted to explore the possibility of using small Cu-Sn clusters, CuSn ( = 0-4), isolated or supported on graphene and γ-AlO, to activate CO and convert it to carbon monoxide (CO) and formic acid (HCOOH). First, a detailed analysis of the structure, stability, and electronic properties of CuSn clusters and their ability to absorb and activate CO was considered. Then, the kinetics of the gas phase CO direct dissociation on CuSn to generate CO was determined. Finally, the mechanism of electrocatalytic CO reduction to CO and HCOOH on CuSn, CuSn/graphene and CuSn/γ-AlO was computed. The selectivity towards the competitive electrochemical hydrogen evolution reaction on these catalysts was also considered. The CuSn cluster suppresses the hydrogen evolution reaction and is highly selective towards CO, if unsupported, or HCOOH if supported on graphene. This study demonstrates that the CuSn cluster is a potential candidate for the electrocatalytic conversion of the CO molecule. Moreover, it identifies insightful structure-property relationships in Cu-based nanocatalysts, highlighting the influence of composition and catalyst support on CO activation.