ZnSe/V 2 C 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 V 2 C 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 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 Na 2 S/Na 2 SO 3 solution, which is significantly higher than that of pristine ZnSe or V 2 C MXene. This study not only elucidates the fundamental mechanism of charge migration in 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 nextgeneration photocatalytic materials.