Predicting pseudocapacitive adsorption isotherms through quantum-continuum calculations

Pseudocapacitive electrodes function through redox reactions that occur on the surface of the electrode allowing for high charging/discharging rates. Complex interfaces cause much to be unknown about the pseudocapacitive process. Computational modeling has made progress in predicting the response of these systems but further research is needed to optimize performance. A theoretical approach is developed to study pseudocapacitive systems, focusing on ruthenium dioxide (RuO₂). Material properties from quantum-continuum simulations are combined with Monte Carlo sampling to predict adsorption isotherms. Computational findings for the RuO₂ (110) surface show good agreement with experimental data where the double-layer contribution is shown to be a small fraction of the overall electrochemical response but controls to a the overall pseudocapacitive response of the electrode. By focusing on the double-layer contribution, different trends emerge based on the surface orientation. For RuO₂ (110), the double-layer capacitance from electronic-structure methods show a small spread while a downward trend is seen for (100) with increasing coverage. By using double-layer capacitance predicted from first principles, good agreement is reached with experiment along the (100) surface orientation.