Recently, developing high-efficiency photocatalytic hydrogen generation photocatalysts and clarifying the inherent mechanism behind the enhancement of hydrogen generation activity have been the research focus. Here, we present a step-wise strategy to prepare PtiTiO(2)/reduced graphene oxide photocatalysts and the inherent mechanism of the enhanced photocatalytic activities were systematically investigated. Experimentally, the 2 wt% rGO doped rGO/Pt-TiO2 nanocomposites showed the superior solar-driven hydrogen generation rate (1075.68 mu mol h(-1) g(-1)), which was 81 times and 5 times higher than bare TiO2 and Pt/TiO2 samples, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectra (FT-IR) demonstrated the formation of Ti-O-C bonds in the hybrid, which drove the shifting upwards of the valence band edge from +2.2 eV to +1.83 eV. Furthermore, pliotoelectrochemical tests indicated the electron density of PTG-2 was about one order of magnitude higher than TiO2. Moreover, DFT calculations displayed that the bandgap had been successfully narrowed from 2.88 eV to 2.76 eV and the original blank energy region located at TiO2 bandgap was filled with C2p orbitals, which resulted in excited electrons in TiO2 efficiently transferring to graphene. Consequently, the DFT calculations are in good agreement with the experimental results and physical characterizations. This study affords us a rational design of a high efficiency photocatalytic system for solar energy conversion. (C) 2017 Elsevier B.V. All rights reserved.