Insight into charge carrier separation and solar-light utilization: rGO decorated 3D ZnO hollow microspheres for enhanced photocatalytic hydrogen evolution.

Improving efficient solar light utilization, facilitating charge transportation and reducing electron-hole recombination, are the three major challenges in photocatalysis, and numerous interests have been devoted into overcoming these issues for obtaining high performance photocatalysts. Herein, ZnO hollow microspheres/reduced graphene oxide (ZnO/rGO) composites were constructed as a high performance photocatalyst for splitting water into H2 via a one-step microwave-assisted solvothermal process. The optimized ZnO/rGO nanocomposite (the mass ratio of GO to ZnO is 1%) reached a maximum H2 evolution rate of 648.1 μmol/h/g without using noble metal as cocatalyst, which exhibiting ~2.3-fold enhancement as compared to that of the bare ZnO. This significant improvement was primarily attributed to great light-harvesting capacity and the efficient charge carrier separation and transfer. The detailed characterization of PL and EIS revealed that, in the ZnO/rGO composite, the rGO nanosheets played important roles in promoting the charge carrier separation and transfer, which therefore resulting in an enhanced activity in H2 evolution. Our present observations provide a valuable methodology for exploring novel high performance photocatalyst, especially in graphene-based inorganic hybrid systems.