Modulating Activity and Selectivity of CO 2 Electroreductions at Au–Water Interfaces via Engineering Local Cation Condition

High Resolution Image Download MS PowerPoint Slide The mechanistic understanding of the CO 2 reduction reaction (CO 2 RR) under electrochemical conditions is crucial for optimizing the overall catalytic performance. While electrolyte ions have received considerable attention, it remains unclear how the condition of interfacial cations modulates the CO 2 RR and the competitive hydrogen evolution reaction (HER) at the electrode–electrolyte interfaces. Herein, we explore the CO 2 activation and Volmer step representing the critical first electron transfer during the CO 2 RR and HER, respectively. This investigation involves manipulating the cation identity (K +, Li +, and H + ) and concentration at Au–water interfaces, which is carried out via the slow-growth sampling approach integrated with ab initio molecular dynamics simulations. Our results demonstrate that the high local alkali metal cation (AM + ) concentration facilitates the CO 2 RR following the order of 2K + > 1K + > 2Li + > 1Li + > 0AM +, and the highly promoted CO 2 activation kinetics originate from the short-range coordination between alkali metal cations and reaction intermediates. However, the interfacial HER behaves very differently with the kinetic order of 1Li + > 0AM + > 1K + > 2Li + > 2K +, closely related to the interfacial water structures, which are affected by both cation identity and local concentrations. Overall, the activity and selectivity of the CO 2 RR at the Au–water interface can be enhanced by increasing the local cation concentration (K + > Li + ). These findings highlight the critical roles of alkali metal cations and reaction microenvironments in modulating interfacial reaction kinetics.