Understanding and leveraging the effect of cations in the electrical double layer for electrochemical CO2 reduction

The electrical double layer formed at the electrode-electrolyte interface has significant impacts on electrochemical reactions that have been inadequately acknowledged. For electrochemical CO2 reduction reaction, larger alkali cations are generally found to promote the activities on a number of catalysts. Understanding and leveraging the intriguing cation effect would enable us to steer this challenging reaction toward desirable directions. Several hypotheses have been proposed since the discovery of the effect decades ago. But there is yet no consensus on its underlying mechanism. In this perspective, we overview the current understanding about the complex nature of the cation effect based on latest experimental and computational findings and discuss how this effect could be leveraged, in combination with the optimization of other conditions, to enable highly efficient CO2 reduction.