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

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 Ag 2 S quantum dots (QDs)/g-C 3 N 4 ) with excellent photocatalytic performance by anchoring the Ag 2 S QDs cocatalyst on the surface of g-C 3 N 4 through a self-assembly strategy. Ag 2 S QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-C 3 N 4 . The Ag 2 S QDs/g-C 3 N 4 composite with 0.5 wt% Ag 2 S 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-C 3 N 4 and Ag 2 S nanoparticles (NPs)/g-C 3 N 4 . Moreover, it was 2.04 times the activity of Pt/g-C 3 N 4 with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of Ag 2 S QDs caused by the quantum size effect and the convenient and effective charge transfer between g-C 3 N 4 and Ag 2 S QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H 2 evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.