In Situ Synthesis of Hybrid-Phase WS₂ with S Defects as a Cocatalyst for the g-C₃N₄-Based Photocatalytic Hydrogen Evolution Reaction

Due to the reliance on expensive noble metal cocatalysts and complex synthesis routes for its composite, the practical application of graphitic carbon nitride (g-C3N4) still remains uncertain. In this work, a simple synthesis strategy based on an in situ gas–solid phase reaction was employed to prepare 1T/2H hybrid WS2 as a non-noble metal cocatalyst for g-C3N4. Specifically, during the typical process of preparing g-C3N4 by the thermal condensation of thiourea, the precursor WO3 fully mixed with thiourea was simultaneously sulfided to 1T/2H hybrid WS2 via an in situ gas–solid phase reaction by the escaping byproduct H2S. Benefiting from the introduction of the hybrid crystal phase and the existence of S defects in WS2, the photocatalytic hydrogen evolution ability of the catalyst enhanced obviously, which increased from 0.32 to 34.76 μmol·h–1. The hydrogen evolution overpotential of the catalyst was reduced, and the migration and separation abilities of photogenerated carriers were effectively improved due to the cocatalyst WS2. A convenient strategy to synthesize a g-C3N4-based photocatalyst combined with transition metal disulfides (TMDs) was provided in this work for enhanced carrier separation ability.