Understanding the Role of Electrolyte Cations on Activity and Product Selectivity of CO2 Reduction over Cu Electrode

Abstract

The electrocatalytic conversion of CO2 on a Cu electrode has the potential to produce valuable chemicals such as hydrocarbons and oxygenated compounds. While the influence of electrolyte cation on the activity and selectivity of the CO2 reduction reaction (CO2RR) on Cu has been widely observed, the specific mechanism through which cation species affect the CO2RR remains unclear and subject to debate. In this work, the CO2RR in the carbonate electrolytes containing different alkali metals (Li+, Na+, K+, Rb+, and Cs+) was investigated at potentials from −0.1 to −1.1 V (vs. RHE) over a Cu electrode using electrochemical techniques. Charge transfer kinetics, adsorption of species, and mass transport were considered comprehensively during the analysis. It is found that several factors can play a role in the CO2RR, including hydrated cation adsorption, preferential hydrolysis, and interaction between the cation and adsorbed species, with the dominating factor determined by the external bias and cation species. Consequently, a coherent interpretation of the influence of electrolyte cations on the intrinsic kinetics of the CO2RR has been put forward. We envision that these insights will greatly contribute to the development of efficient catalytic systems and the optimization of catalytic conditions, thereby advancing progress toward commercial applications in this field.