ZnSe/V2C MXene Schottky junction: mechanism of interface barrier promoting carrier directional separation and enhancing photocatalytic hydrogen evolution

Abstract

ZnSe is a promising photocatalyst but suffers from a high recombination rate of photogenerated charge carriers and inefficient charge transfer, which limit its photocatalytic activity. To address these issues, a Schottky junction composite catalyst was constructed by in situ growth of ZnSe nanoparticles on the surface of V₂C MXene. The metallic-like conductivity of MXene provides efficient electron transport pathways, which facilitates rapid electron migration and suppresses the recombination of photogenerated electron–hole pairs. The mechanism of photogenerated charge transfer was studied by photoelectrochemical measurements, Kelvin probe force microscopy (KPFM) and in situ irradiation X-ray photoelectron spectroscopy (XPS). The results show that band bending and an internal electric field are formed at the heterogeneous interface, which provide a physical basis for the formation of the interface barrier and effectively promote the separation and transfer of carriers. Benefiting from these synergistic effects, the composite catalyst ZV-3 exhibits a remarkable hydrogen evolution rate of 2154.00 μmol g⁻¹ h⁻¹ in a Na₂S/Na₂SO₃ solution, which is significantly higher than that of pristine ZnSe or V₂C MXene. This study not only elucidates the fundamental mechanism of charge migration in a Schottky junction, but also provides a strategy for designing high-performance photocatalytic systems. The proposed approach offers promising prospects for efficient solar-to-hydrogen conversion and the development of next-generation photocatalytic materials.