Mechanistic insights into potassium ion promotion of formate selectivity on copper clusters during carbon dioxide electroreduction

Enhancing efficiency and product selectivity presents a significant challenge in carbon dioxide electroreduction (CO 2 RR). While ions in the electrolyte have been shown to play an important role in the case of bulk copper electrodes, the specific effects of the cation have not been investigated for copper nanoclusters (NC). In this study, an extended model system for quantum chemical simulations is presented, which enables the selective investigation of the specific role of the potassium ion in CO 2 RR. The results showed that the presence of potassium ion leads to more exoergic CO 2 adsorption on the electrode surface. More importantly, after the first reduction step, at higher concentrations, potassium ions facilitate the desorption of formate from the cluster. This indicates that CO 2 RR on copper NCs can be tuned toward formate formation through electrolyte engineering; thus, the process may be an appealing candidate for electrochemical energy storage in the future.