Construction 0D/2D heterojunction by highly dispersed Ag₂S quantum dots (QDs) loaded on the g-C₃N₄ nanosheets for...

In recent years, the use of quantum dots (QDs) cocatalysts to improve the hydrogen evolution activity from the water splitting of photocatalysts has become a popular research topic. Herein, we successfully prepared a novel 0 dimension/2 dimension (0D/2D) heterojunction nanocomposite (denoted Ag₂S quantum dots (QDs)/g-C₃N₄) with excellent photocatalytic performance by anchoring the Ag₂S QDs cocatalyst on the surface of g-C₃N₄ through a self-assembly strategy. Ag₂S QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-C₃N₄. The Ag₂S QDs/g-C₃N₄ composite with 0.5 wt% Ag₂S QDs loading achieved the highest hydrogen evolution rate of 471.1 μmol·g^-1·h^-1 with an apparent quantum efficiency (AQE) of 1.48% at 405 nm. Such remarkable hydrogen evolution activity far exceeded that of undoped g-C₃N₄ and Ag₂S nanoparticles (NPs)/g-C₃N₄. Moreover, it was 2.04 times the activity of Pt/g-C₃N₄ with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of Ag₂S QDs caused by the quantum size effect and the convenient and effective charge transfer between g-C₃N₄ and Ag₂S QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H₂ evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.