Engineering Interfacial Dual Vacancies in Heterostructured Electrocatalysts for Efficient Overall Water Splitting

Defect engineering has emerged as a pivotal strategy for tailoring the electrocatalytic activity of electrocatalysts, yet the fundamental mechanisms underlying the role of interfacial dual vacancies remain insufficiently understood. In this study, we rationally designed and synthesized a heterostructured electrocatalyst with interfacial oxygen and sulfur dual vacancies (V_os-Co₃O₄@MoS₂) via a hydrothermal-calcination approach, achieving high efficiency in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Combined experimental and theoretical investigations reveal that Co-O-S-Mo interfacial bonds, together with dual vacancies, synergistically modulate the local electronic environment by shifting the d-band center toward the Fermi level. This adjustment optimizes the adsorption energy of key intermediates, thereby accelerating the reaction kinetics. As a result, the V_os-Co₃O₄@MoS₂ heterostructure demonstrates outstanding bifunctional activity in alkaline media, delivering low overpotentials of 81 mV for HER and 253 mV for OER at 10 mA cm^-2. Additionally, it requires only 1.566 V to drive overall water splitting at 10 mA cm^-2 and maintains excellent stability for over 50 h. This work highlights the critical role of interfacial dual vacancies in enhancing electrocatalytic performance and provides valuable insights for the rational design of high-performance electrocatalysts for sustainable energy applications.