Building {0001} and {101¯1} facet heterojunctions on hexagonal pyramid CdS single crystals with high photoactivity and photostability for hydrogen evolution

Abstract CdS has suitable band gap and high photoelectric conversion efficiency, which has attracted widespread attention. However, its severe photocorrosion and low photocatalytic activity limits its application. Generally, constructing heterojunction structure can effectively improve the separation efficiency of CdS photogenerated carriers, and its photocatalytic activity and stability can be further improved. Here, we prepared CdS hexagonal pyramid single crystal with co-exposed {0001} and {10 1 ¯ 1} crystal planes by the urothermal method. Type II heterojunction can be formed between {0001} and {10 1 ¯ 1} crystal planes, which can effectively improve the photocatalytic hydrogen production activity of CdS hexagonal pyramid. The photocatalytic hydrogen production activity of CdS hexagonal pyramid is 10.64 mmol·h-1·g-1 with an apparent quantum efficiency of 15.6% at 420 nm, which is 5.8 times and 13.2 times as high as CdS nanorod and CdS nanoparticles, respectively. Even after the 100 h cycle test, the CdS hexagonal pyramid shows still high photocatalytic activity. This work showed that the photocatalytic activity can be effectively improved by adjusting the crystal faces, which can further generaliza to other photocatalysts.