Metallic-like WN as electron harvester decorated on sulfur vacancy rich CdS single crystal for boosting photocatalytic hydrogen production

Abstract

Developing efficient, stable, low-cost, and earth-rich cocatalysts has been proven to be an effective strategy for achieving highly active semiconductor-based photocatalytic hydrogen evolution from water splitting. Herein, a Schottky junction was rationally fabricated by noble-metal-free metallic tungsten nitride (WN) and sulfur vacancies-rich CdS single crystals (WN/CdS) for competent photocatalytic H₂ evolution. The density functional theory (DFT) calculation results indicated that metallic properties of WN. Systematic investigations reveal that metallic-like WN can be acted as a novel superior electron harvester to rapid capture and transfer photogenerated charges, which can be confirmed by the fluorescence, time-resolved fluorescence spectra (TRPL) and photoelectrochemical characterization and in-situ XPS. And the sulfur vacancies also can act as electron trappers to enhance carrier separation and electron transfer. Thus, the synergistic effect of sulfur vacancies and Schottky junction greatly enhance the photocatalytic H₂ production activity. In addition, the more negative zeta potential of 10 %WN/CdS means the stronger protons adsorption well as promoted hydrogen evolution activity. The maximum photocatalytic H₂ evolution activity of 15.02 mmol g⁻¹ is achieved over 10 % WN/CdS composite, which is about 2.34 folds of pristine CdS, respectively. Meanwhile, a super photostability over ten consecutive cycles of light irradiation of 100 h is also achieved for photocatalytic hydrogen generation. This work certifies the metallic WN is a promising candidate to construct higher-performance heterostructured photocatalyst for efficient energy conversion.