Regulating metal–oxygen covalency in reconstructed sulfurized high-entropy perovskite to activate and stabilize lattice oxygen for the oxygen evolution reaction

Abstract

Switching the adsorbate evolution mechanism (AEM) to the lattice oxygen mechanism (LOM) can break the theoretical limit of catalytic activity for the oxygen evolution reaction (OER). However, it is difficult for LOM-dominated catalysts to simultaneously obtain high activity and stability because of their trade-off relationship. Here, we report a reconstructed sulfurized high-entropy perovskite (S-LaNiFeCoCrMnO₃), which possesses excellent activity with an overpotential of 165 mV and has a high catalytic stability for 1800 h at 10 mA cm⁻² toward the OER. Furthermore, S-LaNiFeCoMnCrO₃ as the anode catalyst in an anion exchange membrane water electrolyzer exhibits a high current density of 5.8 A cm⁻² at a cell voltage of 2.0 V. On-line differential electrochemical mass spectrometry results suggest that the increased reactivity of lattice oxygen in reconstructed S-LaNiFeCoCrMnO₃ facilitates the enhancement of OER activity. X-ray absorption near-edge structure and in situ Raman spectroscopy results reveal that the local Ni–S bond in the sulfurized layer on the surface of S-LaNiFeCoCrMnO₃ drives the generation of the Fe–NiOOH active phase with a NiO₂ subunit layer and high-valent Ni⁴⁺ species. Furthermore, strong covalent Ni–O and weak covalent Fe–O bonds in the Fe–NiOOH active phase play a critical role in activating and stabilizing lattice oxygen, thus breaking the activity–stability trade-off relationship for the LOM.