A Multi-Paradigm Computational Model of Materials Electrochemical Reactivity for Energy Conversion and Storage

In this paper we report a new multi-paradigm modeling approach devoted to the investigation of the electrochemical reactivity of materials in electrodes for energy conversion or storage applications. The approach couples an atomistically-resolved Kinetic Monte Carlo (KMC) modeling module describing the electrochemical kinetics in an active material, with continuum modeling modules describing reactants transport at the active material/electrolyte nanoscopic interface (electrochemical double layer region) and along the mesoscale electrode thickness. The KMC module is developed by extending the so-called Variable Step Size Method (VSSM) algorithm (called here Electrochemical-VSSM) and constitutes the first VSSM extension reported so far which allows calculating the electrode potential as function of the imposed current density. The KMC module can be parameterized with activation energies calculated from Density Functional Theory (DFT), and thanks to the coupling with the transport modules, it describes the materials reactivity in electrochemical conditions. This approach allows us to study how the surface morphology (e.g. distribution of inactive sites, size of the active material particle, etc.) impacts the performance of the electrode. As an application example, we report here a computational investigation of the Oxygen Reduction Reaction (ORR) kinetics in a Pt(111)-based Polymer Electrolyte Membrane Fuel Cell (PEMFC) cathode.