Composites of Ag-Doped ZnIn2S4 Nanoplates with Graphitic Carbon Nitride and Reduced Graphene Oxide Nanosheets for Sunlight-Driven Hydrogen Production and Water Purification

Photocatalysis is considered a promising technology to alleviate the energy crisis and environmental pollution; however, developing photocatalysts with improved light absorption efficiency is still a challenge. In this work, an effective strategy was proposed to synthesize a highly functional ternary nanocomposite (g-C3N4/RGO/AZIS) by coupling broader light-absorbing Ag-doped ZnIn2S4 (AZIS) nanoplates with ultrathin g-C3N4 and reduced graphene oxide (RGO) nanosheets. The 2D-on-2D stacking nanostructure of the composite provides a compact heterojunction, enlarged interfaces, and enriched active sites, resulting in the accelerated separation and relocation kinetics of charge carriers. Benefiting from these advantages, the g-C3N4/RGO/AZIS nanocomposite with systematically optimized contents of RGO and AZIS can serve as an efficient bifunctional photocatalyst for both H2 production from water splitting and methyl orange (MO) photodegradation under the irradiation of visible light. The H2 production rate of the ternary nanocomposite is 658.5 μmol h–1 g–1, which is 38 times higher than that of plain g-C3N4. The operation mechanism is proposed based on the results of scavenger tests and photoelectrochemical analysis. The formation of a type-II heterostructure between AZIS nanoplates and g-C3N4 nanosheets along with RGO with lower potential can maximize the separation efficiency of photogenerated electron–hole pairs and decrease the charge recombination. This work provides a viable strategy to develop bifunctional photocatalysts with enhanced performance for both H2 production and degradation of organic dyes.