Dual-sulfur defects decorated 1T-WS2/Cd0.5Zn0.5S heterojunctions for boosted photocatalytic hydrogen evolution

Abstract

Defect engineering has emerged as a powerful strategy for enhancing photocatalytic performance. In this paper, a novel dual-defect 1T-WS₂/Cd_0.5Zn_0.5S (WS_v/CZS_v) Schottky heterojunction was successfully fabricated via a combined solvothermal-hydrothermal approach. Electron paramagnetic resonance (EPR) and high-resolution TEM (HRTEM) confirmed the presence of dual sulfur vacancies. The optimized WS_v/CZS_v composite exhibits exceptional hydrogen evolution performance, achieving a remarkable rate of 3060.63 μmol·g⁻¹·h⁻¹, which are 9.83 and 2.54 times higher than that of pure CZS and CZS_v, respectively. Notably, the catalyst maintained over 90 % of its initial activity after four consecutive photocatalytic cycles, demonstrating superior stability. Comprehensive characterization through electrochemical impedance spectroscopy (EIS), steady-state photoluminescence (PL), and transient photocurrent measurements revealed that the dual-defect system significantly enhances carrier separation efficiency. This improvement arises from three synergistic effects: electron-trapping capability of dual defect sites, elevated Schottky barrier, and superior electrical conductivity of the 1T-WS₂. Furthermore, the metallic characteristics and sulfur vacancies in 1T-WS₂ synergistically provide abundant active sites for photocatalytic hydrogen evolution on both basal planes and edges. Density functional theory (DFT) calculations indicate that the dual defects optimize charge distribution and achieve an ideal hydrogen adsorption free energy. The energy band alignment and charge transfer mechanism were systematically investigated using Mott-Schottky (M-S) analysis and ultraviolet photoelectron spectroscopy (UPS). This work explores the synergistic interactions between different types of sulfur defects and provides new insights into the coupling of defect engineering.