Quantum Chemical Modeling of the Oxygen Evolution Reaction on Transition Metal Oxide-Based Catalysts

Abstract

Electrochemical and photocatalytic water splitting are crucial processes for sustainable hydrogen production, offering clean alternatives to the use of fossil fuels. The oxygen evolution reaction (OER) plays a limiting role in the conversion of water into oxygen and hydrogen due to its slow kinetics. Therefore, finding economically viable and effective OER catalysts is a continuous challenge in improving the water-splitting process. In this thesis, we investigate the electrocatalytic and photocatalytic abilities of transition metal oxide-based systems towards the OER using first-principles calculations. First, we use density functional theory calculations to examine the catalytic activities of first-row transition metal (oxy)hydroxide complexes (Ti, Mn, Fe, Co, Ni) towards the OER process. The results provide detailed information related to the mechanistic pathways and the electrocatalytic efficiencies of the metal complexes. Our calculations also show how the coordination environment and metal substitution affect the electrocatalytic efficiency. Next, we investigate the multiple potential OER mechanisms and the energetics of the associated reaction intermediates on Se-doped TiO2 anatase (101) surfaces. The calculations indicate that moderate Se doping levels can improve OER activity on TiO2. Our results also show the effect of Se coverage on the stability of TiO2 (101) and demonstrate how different Se doping coverages affect the electronic properties of the TiO2 anatase surface. Finally, we examine the light absorption properties of Se-doped TiO2 (101) surfaces using the random-phase approximation method. Calculations of the electronic properties and dielectric constant profiles show that the optical activity of the TiO2 surface in the visible range can be significantly improved by Se-doping. The spatial distributions of electron-hole pairs associated with low-lying excitations in the doped surfaces demonstrate that photogenerated electrons and holes are spatially well separated on the Se-doped surfaces. Further analysis of the behavior of photogenerated electrons and holes on the Se-doped and undoped TiO2 surfaces with selected reaction intermediates provides insights into the role of doped Se and adsorbed species on the surface in promoting photocatalytic OER.