Unveiling the electrolyte effects of CO2 electroreduction to CO and H2 evolution from the interfacial pH perspective

Abstract

The role of the interfacial environment during electrochemical reactions has been increasingly valued, especially for those reactions involving protons or hydroxyl ions. The acid-base equilibria of the weak proton donors in the bulk electrolyte, namely the protic anions and the weakly hydrated cations, implicitly modify the interfacial environment and impact the rate and selectivity of electrochemical reactions. Therefore, the interfacial pH is key to unveil the electrolyte effects. In this thesis, we devised an in-situ interfacial pH sensor and visualized the evolution of interfacial pH during the electroreduction of CO2 to CO and H2 evolution. We found that the reaction activity and competition between CO2 electroreduction to CO and H2 evolution is highly dependent on interfacial pH, which can be readily tuned by modulating the interfacial environment via various electrolyte species.