Activation of Lattice Oxygen in Nitrogen-Doped High-Entropy Oxide Nanosheets for Highly Efficient Oxygen Evolution Reaction

Abstract

High-entropy oxides (HEOs) are potential electrocatalysts for overcoming the sluggish kinetics of the oxygen evolution reaction (OER). Conventionally, the thermodynamic barrier of the lattice oxygen mechanism (LOM) is lower than that of the adsorbate evolution mechanism (AEM). However, controlling the transition from the AEM to the LOM remains challenging. Herein, an in situ modulation strategy has been developed to synthesize N-FeCoNiAlMoO x by introducing structural directing agents and electronic modulators. Different instruments were used to identify the nitridation-triggered micromorphologies and phase transformations. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS) reveal the optimized electronic structures after nitrogen doping. N-FeCoNiAlMo x exhibits OER performance with low overpotentials of 240 and 285 mV at 10 and 100 mA·cm –2, respectively. pH dependence, free-radical capture experiments, and density functional theory (DFT) calculations confirm that nitrogen doping facilitates the LOM pathway. This work elucidates nitrogen’s critical role and the LOM pathway’s contribution to efficient OER performance.