Highly efficient visible-light photocatalytic H2 evolution over 2D–2D CdS/Cu7S4 layered heterojunctions

Converting solar energy into clean and sustainable chemical fuels is a promising strategy for exploiting renewable energy. The application of photocatalytic water splitting technology in hydrogen production is important for sustainable energy development and environmental protection. In this study, for the first time, 2D Cu7S4 co-catalysts were coupled on the surface of a CdS nanosheet photocatalyst by a one-step ultrasonic-assisted electrostatic self-assembly method at room temperature. The as-fabricated 2D–2D CdS/Cu7S4 layered heterojunctions were demonstrated to be advanced composite photocatalysts that enhance the water splitting efficiency toward hydrogen production. The highest hydrogen evolution rate of the 2D–2D CdS/2%Cu7S4 binary heterojunction photocatalyst was up to 27.8 mmol g−1 h−1 under visible light irradiation, with an apparent quantum efficiency of 14.7% at 420 nm, which was almost 10.69 times and 2.65 times higher than those of pure CdS nanosheets (2.6 mmol g−1 h−1) and CdS-2%CuS (10.5 mmol g−1 h−1), respectively. The establishment of the CdS/Cu7S4 binary-layered heterojunction could not only enhance the separation of photogenerated electron–hole (e−–h+) pairs, improve the transfer of photo-excited electrons, and prolong the life-span of photo-generated electrons, but also enhance the light absorption and hydrogen-evolution kinetics. All these factors are important for the enhancement of the photocatalytic activity. Expectedly, the 2D–2D interface coupling strategy based on CdS NSs can be extensively exploited to improve the hydrogen-evolution activity over various kinds of conventional semiconductor NSs. The 2D/2D CdS/Cu7S4 layered heterojunctions were, for the first time, fabricated by a one-step ultrasonic-assisted electrostatic self-assembly, which could reach a visible-light H2-generation rate of 27.8 mmol g−1 h−1, with an apparent quantum efficiency of 14.7% at 420 nm.