Size effect of CoS2 cocatalyst on photocatalytic hydrogen evolution performance of g-C3N4

The main goal of researchers is to obtain cheap cocatalysts that can promote the photocatalytic activity of catalysts. In this work, a series of CoS2/g-C3N4 (denoted as CoS2/CN) composite photocatalysts were synthesized by photodepositing CoS2 on g-C3N4 surface. The size of CoS2 species could be tuned from single-atom to nanometer scale, which had effect on photocatalysis. The 5CoS2/CN sample with proper nano size of CoS2 cocatalyst had the best photocatalytic performance (1707.19 μmol g-1h-1) in producing H2 under visible light irradiation (λ > 420 nm). Its photocatalytic activity was about 1434.6 times higher than that of pure g-C3N4 and almost equal with that of Pt/CN catalyst (1799.54 μmol g-1h-1). The Density Functional Theory (DFT) calculation results further suggested that the ability of accumulating the electrons of the cocatalyst was based on the size effect of CoS2, and the proper size of the cocatalyst efficiently promoted the separation of photogenerated electron-hole pairs.