MODELING DIVERSE PROCESSES AT OXIDE INTERFACES

As the world continues warming, the need for new materials in sustainable technologies only growsmore urgent. This thesis uses ab initio methods including density functional theory in concert with molecular dynamics, enhanced sampling techniques, and microkinetic modeling to study oxide materials as applied to carbon mineralization, the oxygen evolution reaction, and electrochemical ammonia synthesis. First, carbon mineralization–a strategy for removing atmospheric CO2 by reaction with alkalinity in specific mineral oxides–is addressed. The dissolution rates of Mg- and Ca-containing mineral oxides are shown to be highly surface dependent. Similarly, for the acidic oxygen evolution reaction, transition metal oxide catalysts expose different facets and have different adsorbate coverages depending on material and reaction conditions. Multi-facet Pourbaix diagrams are presented that enable bulk and surface stability conclusions to be visible in one plot. Next, high temperature ammonia synthesis using BaZrO3-based ceramic proton conducting electrolytes is studied. Migration of protons from the electrolyte bulk to the surface followed by hydrogen evolution without the need for a recombination catalyst is shown to be a favorable process and the implications on nitrogen reduction electrocatalysis are discussed. Using this same electrolyte model surface, microkinetic modeling of electrochemical ammonia synthesis leads to the proposal of a new experimental methodology for improving selectivity at elevated temperatures. Finally, to help reduce the inherent complexity of these materials, a quantitative model for predicting the hybridization energy due to interactions between an adsorbate and a metal oxide surface is presented. The model builds on identification of key surface electronic structure features that dictate the strength of the adsorption interaction. Atomistic computational techniques applied to transition metals revolutionized the fields of catalysis and materials science and this thesis demonstrates that application of these tools to oxide materials offers many reasons to be optimistic going forward.