Simultaneous realization of direct photodeposition and high H2-production activity of amorphous cobalt sulfide nanodot-modified rGO/TiO2 photocatalyst

To realize highly efficient hydrogen production of graphene-based photocatalysts, it is greatly important to increase more interfacial active sites onto graphene. In this work, the highly efficient CoSx-rGO (reduced graphene oxide)/TiO2 composite photocatalyst was synthesized via a simple two-step method, including the hydrothermal loading of rGO nanosheets onto TiO2 nanoparticles and the subsequent photodeposition process of CoSx nanodots (0.5-2 nm) on the rGO nanosheets. Photocatalytic experimental results confirmed that the CoSx-rGO/TiO2 photocatalyst displayed a distinctly higher photocatalytic H-2-evolution activity than the TiO2 photocatalyst. The highest hydrogen-production efficiency of obtained CoSx-rGO/ TiO2 (10%) achieved 256.97 mu mol.h(-1), which was distinctly higher than that of TiO2 (4.41 mu mol.h(-1)), rGO/TiO2 (20.19 mu mol.h(-1)) and CoSx/TiO2 (132.67 mu mol.h(-1)). According to the results of various characterizations and tests, the synergistic-effect mechanism of CoSx nanodots and rGO nanosheets is proposed to explain the increased photocatalytic performance of CoSx-rGO/TiO2 photocatalytic material, namely the rGO nanosheets cause the quick transfer of photo-induced carriers from TiO2 to CoSx nanodots, and then CoSx nanodots work as hydrogenproduction active sites to quickly generate H-2. The present study may offer innovative ideas for the preparation and application of new highly efficient and inexpensive photocatalytic materials.

Automated summary

In order to achieve highly efficient hydrogen production, it is crucial to increase interfacial active sites on graphene-based photocatalysts. The CoSx-rGO/TiO2 composite photocatalyst showed significantly higher hydrogen evolution activity compared to TiO2, with the synergistic effect between CoSx nanodots and rGO nanosheets playing a key role in enhancing photocatalytic performance. This study provides innovative ideas for the development of new highly efficient and cost-effective photocatalytic materials.