Simultaneous realization of direct photodeposition and high H_(2)-production activity of amorphous cobalt sulfide nanodot-modified rGO/TiO_(2)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 CoS_(x)-rGO(reduced graphene oxide)/TiO_(2) composite photocatalyst was synthesized via a simple two-step method,including the hydrothermal loading of rGO nanosheets onto TiO_(2) nanoparticles and the subsequent photodeposition process of CoS_(x) nanodots(0.5-2 nm) on the rGO nanosheets.Photocatalytic experimental results confirmed that the CoS_(x)-rGO/TiO_(2) photocatalyst displayed a distinctly higher photocatalytic H_(2)-evolution activity than the TiO_(2) photocatalyst.The highest hydrogen-production efficiency of obtained CoS_(x)-rGO/TiO_(2)(10%) achieved 256.97 μmol·h-1,which was distinctly higher than that of TiO_(2)(4.41 μmol·h-1),rGO/TiO_(2)(20.19 μmol·h^(-1)) and CoS_(x)/TiO_(2)(132.67 μmol·h^(-1)).According to the results of various characterizations and tests,the synergistic-effect mechanism of CoS_(x) nanodots and rGO nanosheets is proposed to explain the increased photocatalytic performance of Co S_(x)-rGO/TiO_(2) photocatalytic material,namely the rGO nanosheets cause the quick transfer of photo-induced carriers from TiO_(2) to CoS_(x) nanodots,and then CoS_(x) 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.