Water oxidation and oxygen reduction are two fundamental reactions important for the storage and utilization and renewable energy resources. Water oxidation, often termed the oxygen evolution reaction (OER), represents the anodic half reaction responsible for conversion of electrical energy into chemical energy via water splitting. The other half reaction, hydrogen evolution (HER), generates H2 as a fuel source. The recombination of O2 and H2 inside a hydrogen fuel cell then converts this stored energy back to electricity when demanded. The oxygen reduction reaction (ORR) is therefore equally important to OER in terms of being able to effectively use the energy stored in H2 and O2.
2H2O –> O2 + 4H+ + 4e– OER
O2 + 4H+ + 4e– –> 2H2O ORR
In collaboration with the Comes group in the Department of Physics at Auburn University, we investigate metal oxide catalysts capable of driving OER and ORR to better understand their fundamental activity, structure, and stability. Specifically, perovskite and spinel oxide materials are grown synthetically using molecular beam epitaxy (MBE) to produce atomically precise and single crystal thin films (10-50 nm). Our group then studies the electrocatalysis of these materials towards OER and ORR. As perovskite and spinel oxides are abundantly studied in the research community for OER and ORR applications, we are particularly interested in characterizing the activity of particular surface terminations (e.g. (100), (111)) which can be controlled precisely using MBE. Such studies cannot be performed with bulk oxides and even nanocrystalline materials. We are also interested in co-synthesis of perovskite-spinel nanocomposite materials with MBE. Controlling growth conditions can produce two unique crystal phases on the same surface with the goal of producing composite materials which are optimized for both OER and ORR activity.
Publications related to this work:
- “Oxygen Reduction Electrocatalysis with Epitaxially Grown Spinel MnFe2O4 and Fe3O4“ ACS Catal. 2022, 12, 3577-3588.
- “Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO3 Thin Films” J. Mater. Chem. A 2022, 10, 1909-1918.