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

Carbon dioxide (CO 2 ) conversion to value-added chemicals is an attractive solution to reduce globally accelerating CO 2 emissions. Among the non-precious and abundant metals tested so far, copper (Cu) is one of the best electrocatalysts to convert CO 2 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, Cu 4− n Sn n ( n = 0-4), isolated or supported on graphene and γ-Al 2 O 3 , to activate CO 2 and convert it to carbon monoxide (CO) and formic acid (HCOOH). First, a detailed analysis of the structure, stability, and electronic properties of Cu 4− n Sn n clusters and their ability to absorb and activate CO 2 was considered. Then, the kinetics of the gas phase CO 2 direct dissociation on Cu 4− n Sn n to generate CO was determined. Finally, the mechanism of electrocatalytic CO 2 reduction to CO and HCOOH on Cu 4− n Sn n , Cu 4− n Sn n /graphene and Cu 4− n Sn n /γ-Al 2 O 3 was computed. The selectivity towards the competitive electrochemical hydrogen evolution reaction on these catalysts was also considered. The Cu 2 Sn 2 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 Cu 2 Sn 2 cluster is a potential candidate for the electrocatalytic conversion of the CO 2 molecule. Moreover, it identifies insightful structure-property relationships in Cu-based nanocatalysts, highlighting the influence of composition and catalyst support on CO 2 activation. Density functional theory calculations of the CO 2 reduction on Cu-Sn clusters, isolated or supported on graphene and γ-Al 2 O 3 , show Cu 2 Sn 2 on graphene to suppress the hydrogen evolution reaction and be highly selective towards the synthesis of formic acid.