Electrode Potential Dependent Differential Capacitance in Electrocatalysis: a Novel, Ab Initio Computational Approach

Abstract: As interest in nanomaterials grows, ab initio simulations play a crucial role in designing electrochemical catalysts. Electrochemical reactions depend on electrode potential, highlighting the importance of the grand canonical representation, especially when integrated with Density Functional Theory. The Grand Canonical Potential - Kinetics (GCP-K) method is a valuable approach for determining electrocatalytic reaction mechanisms and kinetics rooted in quantum mechanics, relying on assumptions of quadratic free energy dependence on charge and a constant differential capacitance-potential relationship. However, it is known that differential capacitance is potential-dependent in several practical electrocatalysts. Here we present $\mu$-GCP-K, a practical approach which makes no assumptions about the relationships between thermodynamic and electrochemical properties. We demonstrate the method's efficiency by computing the surface charge density and differential capacitance of graphene, further emphasizing the importance of accurately calculating the thermodynamic stability of reaction intermediates in carbon dioxide electroreduction, while also showing the role of potential-dependent differential capacitance.