Modeling Fast Energy Storage Reactions in RuO₂ Pseudocapacitors under Realistic Conditions.

Pseudocapacitors are electrochemical devices that exhibit battery-like energy densities and supercapacitor-like power densities. Ruthenia (RuO₂) pseudocapacitor electrodes have high charge storage arising from redox reactions at the surface of the material in a liquid electrolyte. We simulate the response of RuO₂ under surface strain at various pH including interface polarization due to an applied voltage. We use the self-consistent continuum solvation (SCCS) model implemented in the Quantum-Espresso code to produce a database of free energies for several configurations of adsorbed hydrogen atoms on the electrode surface. This database is processed with grand canonical Monte Carlo sampling under various voltage conditions. These computational results elucidate the interfacial mechanisms that control the charge storage performance of RuO₂ electrodes.