AuPd bimetallic nanoparticle (NP) modified ultra -thin graphitic carbon nitride nanosheet photocatalysts were synthesized via photochemical deposition-precipitation followed by hydrogen reduction. The crystal structure, chemical properties, and charge carrier behavior of these photocatalysts were characterized by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS), transient photovoltage spectroscopy (TPV), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and UV-Vis diffuse-reflectance spectroscopy (DRS). Photocatalytic H-2 evolution experiments indicate that the hydrogen treated AuPd nanoparticles can effectively promote the separation efficiency of electron-hole pairs photo-excited in the g-C3N4 photocatalyst, which consequently promotes photocatalytic H-2 evolution. The 1.0 wt% AuPd/g-C3N4 (H-2) composite photocatalyst showed the best performance with a corresponding photocatalytic H-2 evolution rate of 107 mu mol h(-1). The photocatalyst can maintain most of its photocatalytic activity after four photocatalytic experiment cycles. These results demonstrate that the synergistic effect of light reduction and hydrogen reduction of AuPd and g-C3N4 help to greatly improve the photocatalytic activity of the composite photocatalyst. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.