Mechanism of Potential-Dependent CO<sub>2</sub> Reduction and H<sub>2</sub> Evolution during Electrocatalytic CO<sub>2</sub> Process
Zhanzhao Fu, Chunyao Fang, Sihang Liu, Ang Cao, Jianhua Yan
Abstract
Developing effective strategies to suppress the hydrogen evolution reaction (HER) under high potentials is pivotal for industrializing the electrocatalytic CO 2 reduction reaction (CO 2 RR). However, progress remains constrained by an insufficient mechanistic understanding of the potential-dependent competition between CO 2 RR and HER. Motivated by previous experimental endeavors, we perform a systematic theoretical probing into the mechanism of HER and CO 2 RR under varying potentials over Cu as the prototype and find that potential-modulated interfacial K + concentrations govern the HER/CO 2 RR selectivity transition. Specifically, the distinct K + distribution state induced by different potentials can impose a distinguished effect on the free energy barriers of the rate-determining step (RDS) of HER and CO 2 RR, making HER or CO 2 RR the dominant reaction under different situations. The proposed innovative insights into reaction mechanisms can well unveil the experimentally observed potential-dependent HER/CO 2 RR antagonism and inspire us to propose a feasible strategy to inhibit HER over Cu-based catalysts, i.e., maintaining a CO 2 RR-favored cation concentration near the reaction interface under high potentials.