Visible-light-driven water splitting by yolk-shelled ZnIn2S4-based heterostructure without noble-metal co-catalyst and sacrificial agent

The exploitation of low-cost, high-performance and visible-light-activated photocatalysts is of great significance for hydrogen economy. Herein, we report the rational design of a ZnIn2S4-based noble-metal-free photocatalyst for direct splitting of water into H-2 and O-2. Semi-metallic NiCo2S4 with low reduction barrier is selected as H-2 evolving co-catalyst under the guidance of density functional theory (DFT) computation. Controllable preparation of hierarchical heterostructure is achieved by fine-tuning NiCo2S4 yolk-shell hollow spheres from metalorganic framework (MOF) precursors, followed by tight growth of ZnIn2S4 nanosheets on its outer surface and decoration of O-2 evolving co-catalyst, Co3O4 nanoparticles, on the outermost layers. Locating reduction and oxidation sites on interior and exterior surfaces of ZnIn2S4 effectively harness the charge recombination as well as undesired back reaction. As a result of directional charge separation, ZnIn2S4 modified with separated dual cocatalysts exhibits promising photocatalytic activity, which is superior to most of analogous sulfide-based photocatalysts.

Automated summary

This study reports the rational design of a ZnIn2S4-based noble-metal-free photocatalyst for splitting water into H-2 and O-2, achieving promising photocatalytic activity through the precise control of NiCo2S4 structure and the controllable preparation of hierarchical heterostructure. The directional charge separation in ZnIn2S4 modified with separated dual cocatalysts effectively enhances the performance of the photocatalyst, surpassing most similar sulfide-based photocatalysts.