Construction 0D/2D heterojunction by highly dispersed AgS quantum dots (QDs) loaded on the g-CN 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 AgS quantum dots (QDs)/g-CN) with excellent photocatalytic performance by anchoring the AgS QDs cocatalyst on the surface of g-CN through a self-assembly strategy. AgS QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-CN. The AgS QDs/g-CN composite with 0.5 wt% AgS QDs loading achieved the highest hydrogen evolution rate of 471.1 μmol·g·h with an apparent quantum efficiency (AQE) of 1.48% at 405 nm. Such remarkable hydrogen evolution activity far exceeded that of undoped g-CN and AgS nanoparticles (NPs)/g-CN. Moreover, it was 2.04 times the activity of Pt/g-CN with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of AgS QDs caused by the quantum size effect and the convenient and effective charge transfer between g-CN and AgS QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.