Highly mixed high-energy d-orbital states enhance oxygen evolution reactions in spinel catalysts

Design, synthesis, and engineering of electrocatalysts for the oxygen evolution reaction (OER) are essential for attaining desirable electrocatalytic performance towards practical implementation. Emerging spinel-type OER catalysts have not reached the desirable activity and durability, thus demanding critical research to advance the field. To achieve enhanced OER performance for spinel-type OER catalysts, we present an efficient strategy of electronic structure modulation of central metal atoms. Modulation of the electronic properties of the Zn and Co atoms through the counter anionic components (O, S, and Se) regulates the adsorption of oxygen intermediates and thus enhances OER activity, which is systematically demonstrated using Density Functional Theory (DFT) calculation. Although the zinc cobalt selenide catalyst showed the less pronounced trigonal distortion, the mixing of e_g orbitals with selenium accounts for the experimentally observed enhancement in OER activity. The result is, in contrast to the benchmark catalyst made of RuO₂, ZnCo₂Se₄@rGO demonstrated lower OER overpotential (η₁₀ = 302 mV) and Tafel slope (58 mV dec⁻¹) as well as greater durability at 10 mA cm⁻² for 50 h. The implementation of this strategy in several spinel-type catalysts could improve their electrocatalytic performance.