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

Carbon dioxide (CO2) conversion to value-added chemicals is an attractive solution to reduce globally accelerating CO2 emissions. Among the non-precious and abundant metals tested so far, copper is one of the best CO2 catalysts capable of converting this molecule into more than thirty different hydrocarbons and alcohols. However, the selectivity for desired products is often too low. Here, we present a computational investigation of nanostructuring and Cu/Sn alloying effects on the activity and selectivity of CO2 conversion. We have employed density functional theory calculations to explore the possibility of using small Cu−Sn clusters, Cu4−nSnn (n = 0–4), to activate CO2 and convert it to carbon monoxide (CO) and formic acid (HCOOH). First, we have considered a detailed analysis of the structure, stability, and electronic properties of Cu4−nSnn clusters and their ability to absorb and activate CO2. Then, we report the kinetics of the gas phase CO2 direct dissociation on Cu4−nSnn to generate CO. Finally, we discuss the mechanism of electrochemical CO2 reduction to CO and HCOOH on Cu4−nSnn clusters and the competition with the hydrogen evolution reaction. Based on our results, we conclude the Cu2Sn2 system has the highest potential as a stable and selective catalyst for the electrochemical CO2 conversion to CO. We found the Cu2Sn2 to suppress the competitive hydrogen evolution and be highly selective toward CO. This study demonstrates that Cu2Sn2 clusters are a potential candidate for the electrocatalytic conversion of the CO2 molecule. Moreover, it identifies insightful structure-property relationships for CO2 activation, highlighting the influence of composition on CO2 activation.