Ammonia-Treated Graphene Oxide/ZnIn ₂ S ₄ Nanocomposites for Visible-Light Responsive Photocatalytic H ₂ Production and Cr(VI) Reduction

Photocatalysis is a promising technology that can mitigate the energy crisis and environmental pollution. However, enhancing the light absorption efficiency, charge carrier separation, migration, and delayed recombination of photocatalysts remains a significant challenge. In this study, a simple hydrothermal method was utilized to synthesize a highly efficient nanocomposite (aGO/ZIS) by coupling ammonia-treated graphene oxide (aGO) nanosheets with CTAB-guided ZnIn2S4 (ZIS) nanosheets. The composite forms a tight heterojunction, expands the interface, and enhances the active sites, leading to improved charge carrier separation and faster migration. Benefiting from these advantages, the systematically optimized aGO/ZIS nanocomposite functions as a highly efficient bifunctional photocatalyst for H2 production and Cr(VI) reduction under visible-light (450 nm) irradiation. The H2 production ability of 0.2aGO/ZIS (5498 μmol·g–1 h–1) was 9 and 3 times higher than that of pure ZIS0 (591 μmol·g–1 h–1) and CTAB-assisted ZIS (1804 μmol·g–1 h–1) under visible-light illumination, respectively. Also, the 0.3aGO/ZIS composite effectively reduced 50 ppm of Cr(VI) (99.3%) in 60 min of visible-light (450 nm) irradiation at pH 2 without using any hole scavengers. In both cases, aGO/ZIS exhibited excellent stability and reusability after four consecutive cyclic experiments. Finally, DFT calculation disclosed the improved stability, DOS, and charge transfer ability of the aGO/ZIS composite compared to the pristine ZIS and GO/ZIS, which agrees with the experimental results. This study provides a straightforward strategy to develop bifunctional, highly efficient, and recyclable photocatalysts for efficient H2 evolution and effective Cr(VI) reduction.