Mechanism of Water Dissociation on Metal Oxide Surfaces in Bipolar Membrane Electrolyzers: A First-Principles Calculation

Abstract

Bipolar membranes for water electrolysis, consisting of an acidic cation exchange layer and an alkaline anion exchange layer are a promising means for hydrogen production. The electrolyzer operates the oxygen evolution reaction (OER) under locally basic conditions and the hydrogen evolution reaction (HER) under locally acidic conditions. Water dissociation (WD) occurs within the junction, which is spatially separated from the HER and the OER. It has been shown that the addition of a layer of metal oxide nanoparticles at the junction significantly lowers the overpotential for the process of WD [Science, 2020, 369,1099]. However, the atomistic mechanism by which the metal oxide surface catalyzes the WD is still unclear. We will discuss the theoretical understanding of the WD mechanism at the metal-oxide/water interfaces and investigate the descriptors such as surface pKa, dielectric constants, and adsorption energies, etc. We will combine ab intio molecular dynamics simulations with the electronic structure calculations at the hybrid functional level. Further details of the reaction mechanisms during the WD process will also be explored with the nudged-elastic-band calculations.