Sulfur‐Vacancy Anchoring Suppresses Dynamic Surface Reconstruction in Ni‐Doped ZnS Nanospheres to Trigger the Lattice Oxygen Mechanism

Electrocatalyst surfaces undergo dynamic reconstruction in response to electrochemical potentials, typically initiated at defect sites. The role of vacancies in this reconstruction, however, remains poorly understood, and their correlation with catalytic activity is not well established. This work investigates nickel-doped zinc sulfide with sulfur vacancies (NZS-S_v) as an electrocatalyst for the oxygen evolution reaction (OER), aiming to elucidate the roles of vacancies in the sulfur-based catalyst reconstruction process. By employing a combination of experimental measurements, in situ characterizations, and quantum mechanical calculations, we consistently demonstrate that sulfur vacancies effectively mitigate metal dissolution and suppress surface reconstruction, leading to the formation of a Ni-Zn(OH)₂/ZnS heterojunction structure. In this structure, the weakened Zn─O bond strength at the interface induces the generation of non-bonding states, which drives the lattice oxygen to actively participate in the catalytic OER process. The uniquely designed material exhibits exceptional OER performance in 1.0 m KOH electrolyte, achieving a low overpotential of 180 mV at a current density of 10 mA cm^-2 and a Tafel slope of 48.7 mV dec^-1. This study delivers a fundamental understanding of the roles of vacancies in the reconstruction process and provides significant insights into the OER mechanism over reconstructed catalysts.