CAMP: Predicting energy storage at pseudocapacitor interfaces under realistic conditions from first principles
Pseudocapacitors are emerging energy-storage devices characterized by fast and reversible redox reactions that enable them to store large amounts of electrical energy at high rates. We simulate the response of pseudocapacitive electrodes under realistic conditions to identify the microscopic factors that determine their performance, focusing on ruthenia (RuO2) as a prototypical electrode material. Electronic-structure methods are used together with a self-consistent continuum solvation model to build a complete dataset of free energies as the surface of the charged electrode is gradually covered with protons under applied voltage. The resulting data are exploited to compute hydrogen-adsorption isotherms and charge–voltage responses by means of grand-canonical sampling, finding close agreement with experimental measurements of the energy storage capacity. These simulations offer detailed molecular understanding of the role played by electrolytic conditions in the pseudocapacitive behavior of RuO2, with the ability to capture the influence of the pH, applied voltage, and competition between different surface configurations.