The Computational Cation Electrode: A Case Study on CO2RR.

The electrochemical reduction of CO2 is a promising way to store renewable energy in chemical bonds and convert CO2 to value-added products. In this reaction, the role of electrolyte cations has attracted a lot of attention in the past decade. Nevertheless, computational studies still lack a standardized approach for incorporating cation effects. Here, we introduce a computational cation electrode framework that provides a consistent reference state of metal cations in density functional theory calculations. We first outline the limitations of current reference schemes and then propose a new approach that combines the cation reduction potential with an intermediate bulk state that better mimics the cation in the interface. Using this computational cation electrode framework, we evaluate how the choice of reference influences adsorption energetics across metals and discuss strategies for selecting appropriate bulk states for the computational cation electrode. This work establishes a unified protocol for modeling cation effects in the reduction of CO2 and related electrochemical reactions.