Revealing the size effect of metallic CoS2 on CdS nanorods for photocatalytic hydrogen evolution based on Schottky junction

Abstract The highly efficient photocatalysis of semiconductors by controlling the size of noble metal co-catalysts has been widely used. However, it is unknown whether metallic materials, as a new type of co-catalyst, have a size effect in this process. In this study, by using CTAB (hexadecylcetyltrimethyl-ammonium bromide) as a surfactant, nanocomposites of CoS2/CdS nanorods (NRs) with different loads and sizes of CoS2 were fabricated by using the facile hydrothermal method. The size of the metallic CoS2 nanoparticles (NPs) as co-catalysts could be controlled from ∼ 9 nm to ∼ 45 nm, and the size effect of CoS2 NPs was explored for the photocatalytic evolution of hydrogen. The rate of production of photocatalytic hydrogen of 0.5% CoS2/CdS NR nanocomposites, with ∼ 9 nm CoS2 NPs, was 13 times that of the pristine CdS NRs owing to the maximum difference in work function between CdS and CoS2. The results of experiments and DFT calculations show the effective electron separation and transfer on the CdS NRs through the Schottky junction between CoS2 NPs and CdS NRs. Furthermore, the size effect of metallic materials was verified, which is significant for enhancing the photocatalytic activity of semiconductors.