Synergistic electronic structure modulation of CoVSe via Mott-Schottky heterojunction and se vacancy engineering for...

Synergistically utilizing vacancy and interface engineering to regulate charge transport dynamics represents an effective strategy for enhancing bifunctional electrocatalytic efficiency. In this work, flower-like CoVSe heterostructures with Se vacancies (V_Se-CoVSe) were successfully constructed on MXene-modified nickel foam (NF) through the in-situ transformation of metal-organic framework (MOF) precursors. Both morphological characterizations and density functional theory (DFT) calculations reveal that Se vacancies modulate the local electronic structure of active sites, increasing the defect density of states and shifting the d-band center toward the Fermi level (-0.354 eV). Simultaneously, the work function difference between metallic MXene (4.173 eV) and semiconducting V_Se-CoVSe (4.363 eV) induces a Mott-Schottky effect at the heterojunction to achieve energy level equilibrium. The synergy of the above two mechanisms not only accelerates interfacial charge transfer but also optimizes the adsorption capacity of reaction intermediates, lowering the energy barrier for the oxygen evolution reaction (OER) rate-determining step from 1.730 eV to 1.541 eV. Consequently, the catalyst demonstrates bifunctional activity in 1.0 M KOH, requiring overpotentials of only 144 mV for hydrogen evolution reaction (HER) and 151 mV (OER) at 10 mA cm^-2. This work highlights electronic-state engineering as a viable strategy for the rational design of bifunctional electrocatalysts.