Effect of electrolyte cation-mediated mechanism on electrocatalytic carbon dioxide reduction

The steep reduction in costs and systematic optimization of renewable electricity has ignited an intensifying interest in harnessing electroreduction of carbon dioxide (CO2RR) for the generation of chemicals and fuels. The focus of research over the past few decades has been on the optimization of the electrode and the electrolyte environment. Notably, cation species in the latter have recently been found to dramatically alter the selectivity of CO2RR and even their catalytic activity by multiple orders of magnitude. As a result, the selection of cations is a critical factor in designing catalytic interfaces with high selectivity and efficiency for targeted products. Informed decision-making regarding cation selection relies on a comprehensive understanding of prevailing electrolyte effect models that have been used to elucidate observed experimental trends. In this perspective, we review the hypotheses that explain how electrolyte cations influence CO2RR by mechanisms such as through tuning of the interfacial electric field, buffering of the local pH, stabilization of the key intermediates and regulation of the interfacial water. Our endeavor is to elucidate the molecular mechanisms underpinning cation effects, thus fostering the evolution of more holistic and universally applicable predictive models. In this regard, we highlight the current challenges in this area of research, while also identifying potential avenues for future investigations.