Bandgap Engineering of Ag Nanoclusters-Modified g-C3N4 Nanosheets for Enhanced Photocatalytic Hydrogen Production

Abstract

The photocatalytic hydrogen production rate of graphitic carbon nitride is constrained by its narrow light absorption range and low photogenerated charge carrier separation efficiency. Exfoliating g-C3N4 into ultrathin nanosheets significantly increases the number of active sites and shortens charge migration pathways. However, the quantum confinement effect broadens the bandgap of g-C3N4 nanosheets, thereby impairing light absorption. Here, Ag nanocluster loading onto g-C3N4 nanosheets via immersion thermal reduction introduces bandgap engineering to enhance photocatalytic hydrogen production. Under illumination, 1% Ag-g-C3N4 nanosheets exhibit a remarkably high average H2 generation rate of 7.97 mmol g–1 h–1, which is 2.47, 1.48, and 1.43-fold higher than that of pristine g-C3N4, 0.2% Ag-g-C3N4, and 5% Ag-g-C3N4 nanosheets, respectively. The results indicate that loading Ag nanoclusters onto g-C3N4 nanosheets not only reduces the bandgap from 3.07 to 3.03 eV and raises the conduction band of g-C3N4 but also forms a Schottky barrier that diminishes the recombination of photogenerated charge carriers. The combined effects of increased light absorption capacity, enhanced electron reduction capability, and improved separation efficiency of photogenerated charge carriers lead to a significant enhancement in photocatalytic hydrogen evolution performance. This work presents a strategy for bandgap tuning by loading Ag nanoclusters onto g-C3N4 via immersion thermal reduction.