The synergetic effect of sulfonated graphene and silver as co-catalysts for highly efficient photocatalytic hydrogen production of ZnO nanorods

Hydrogen as a renewable clean energy has attracted much attention, while synthesizing highly efficient materials for photocatalytic hydrogen production remains a great challenge. In this study, we report a new sulfonated graphene (SG)/ZnO/Ag composite as a highly efficient photocatalyst for hydrogen production for the first time. SG/ZnO/Ag composites were prepared through a step-wise approach, including growth of ZnO nanorods on SG sheets by the nanocrystal-seed-directed hydrothermal method and deposition of Ag nanoparticles by the polyol-reduction process. The results show that SG/ZnO/Ag composites achieve a significant high hydrogen evolution rate of 2.36 mmol h^-1 g^-1, which is around 20 times, 3 times and 2.5 times faster than that of pure ZnO rods, ZnO/Ag and SG/ZnO, respectively. The outstanding hydrogen production activity of SG/ZnO/Ag can be attributed to the positive synergetic effects between SG sheets and Ag nanoparticles, which enhance the light absorption ability and facilitate the charge separation activity. Hence, this study highlights that appropriate combination of co-catalysts with photocatalysts can greatly improve the photocatalytic hydrogen production performance.