Recent advances in CdS heterojunctions: morphology, synthesis, performances and prospects

Hydrogen evolution technology by photocatalysts has shown broad prospects in solving the global energy crisis and environmental pollution problems. Cadmium sulfide (CdS) heterojunctions have been concerned as a promising photocatalyst because of its suitable band location, but many challenges are still standing on the way to achieve high photoelectric conversion efficiency and hydrogen evolution activity, such as high carrier recombination rate and poor stability. In this paper, the latest achievements on CdS heterojunctions for hydrogen production were traced. Focusing on the key role of the structure of CdS heterojunctions, the separation and transport of photogenerated charges and hydrogen evolution dynamics during water reduction by CdS heterojunctions photocathode were discussed. Based on the decisive role of material structure on their photovoltaic performance, CdS heterojunctions were divided into three types according to different dimensions, i.e. one dimension, two dimension and three dimension, and their performance characteristics, synthesis methods and application properties were introduced respectively. Finally, the challenges on how to improve the photocatalytic hydrogen evolution efficiency using CdS heterojunctions were brought forward and the structural improvement strategies on designing CdS heterojunctions were proposed. We hope that this review will provide a reference and guidance for the audiences in the field of photocatalysis. The morphology of CdS heterojunctions, which can be rationally designed and fabricated via controllable synthesis approaches, influences their photocatalytic performance.