Study of Al-Doped and Al2O3 Heterostructures for Improving ?-Fe2O3 Catalysis for the Oxygen Evolution Reaction

As a photocatalytic anode material, hematite (alpha-Fe2O3) is the most promising of the three iron oxides. The two other oxides are FeO, which is seldom available, and Fe3O4, which is found naturally in magnetite. There are both theoretical and experimental methods suggested for enhancing alpha-Fe2O3's reactivity. First-principles calculations led to the design of two different doping concentrations of Al-doped alpha-Fe2O3(0001) structures and an Al2O3/ Fe2O3 heterostructure in the (0001) plane. A detailed investigation of the state density and stability, band structure, local potentials, charge densities, and Bader charge analysis is presented in this paper. A reduction in energy was observed with the Al-doping of an alpha- Fe2O3(0001) surface slab. The increase in doping concentration favors the formation of doped systems, and Al's presence in alpha-Fe2O3(0001) is an energetically favorable process. The work function increases by increasing the Al concentration on the surface compared to a pure alpha-Fe2O3(0001) slab. Based on Bader charge analysis and charge density difference studies, it appears that chemical bonding becomes ionic in Al-doped regions. We additionally investigate Al2O3/Fe2O3 interfaces by using first-principles calculations, aiming to shed light on their geometric structure and electronic properties. Al2O3/Fe2O3 interfaces are more thermodynamically favorable. The results of these studies suggest that the Al2O3/Fe2O3 heterojunction is a type-III broken-gap heterojunction rather than a staggered one. Additionally, oxygen evolution reaction (OER) electrocatalysts are discussed for Al-doped systems and the interface. As a result, the most favorable rate-limiting step in high -performance electrocatalysts relies on Al atom doping concentration to modulate the electronic and structural properties of Al-doped sites, while the concentration of active sites is increased and the OER rate is improved. Providing a basic understanding of the OER process at these interfaces, the discussion will be useful for exploring and developing better catalysts and device units.