An Atomic Scale Simulation Framework to Decipher the Complex, High-Temperature Solid Oxide Electrolysis Cell Electro-Chemistries

Solid oxide electrolysis cells (SOECs) have received a significant attention due to their high hydrogen (H2) generation efficiency. However, the major scientific challenges such as low faradaic efficiency of SOECs affects the costs per kilogram of H2 and the large-scale adoption of H2 as a fuel. Therefore, it is imperative to address the fundamental issues surrounding the low faradaic efficiency bottleneck and pave the way for a better SOEC design with a relatively higher faradaic efficiency. In the present research, we present eReaxFF atomic scale simulations workflow that can reproduce quantum mechanical (QM) calculations on relevant condensed phase and cluster systems of solid oxide materials describing oxygen vacancies, vacancy migrations, water adsorption, water splitting and hydrogen generation on the solid oxide material surfaces in a typical electrocatalysis process. We used barium zirconate doped with 20 mol% of yttrium (BZY20) solid oxide as model system. Using the developed eReaxFF force field, we performed zero-voltage molecular dynamics simulations to observe water adsorption and the steps leading to the eventual hydrogen production. In addition, the introduction of explicit electron concept to the force field led to the understanding of the non-zero-voltage effects on hydrogen generation. Based on our simulation results, we conclude that this force field opens an avenue to simulate electron conductivity, electron leakage and provide us a far-reaching molecular understanding of improving the faradaic efficiency of SOECs.