Boosting oxygen evolution reaction performance via metal defect-induced lattice oxygen redox reactions on spinel oxides

Abstract

High-performance and low-cost oxygen evolution reaction (OER) catalysts are essential for sustainable energy-to-hydrogen conversion. Defect engineering has been extensively used to optimize the structure and performance of catalysts. Metal defects have been found to be highly stable relative to oxygen defects in oxygen-rich environments and possess unique electronic structures. However, the formation of metal defects has a high energy cost, and traditional adsorbate evolution mechanism (AEM) catalysts have limited active sites. Here, lattice oxygen-mediated mechanism (LOM) spinel catalysts were successfully fabricated by controllably introducing metal defects to enhance OER efficiency. X-ray absorption spectra indicated that the metal defects induced electron delocalization and redistributed electron density between metal and ligand. Density functional theory calculations revealed that the metal defects elevated the position of the O p-band center, decreased the formation enthalpy of the oxygen defects and altered the adsorption sites, verifying the mechanism switch from the AEM to the LOM. Therefore, the metal defect-enriched ZnFe₂O₄ exhibited enhanced OER activity, delivering a low overpotential of 236 mV @ 10 mA cm⁻² with a small Tafel slope of 67.24 mV dec⁻¹ for the OER in KOH. This work facilitates the development of novel high-performance activated lattice oxygen redox electrocatalysts through cation defect engineering in spinel oxides.