A facile hydrothermal synthesis of few-layer oxygen-doped g-C3N4 with enhanced visible light-responsive photocatalytic activity

•A novel few-layer oxygen-doped g-C3N4 (O-g-C3N4) photocatalyst was prepared.•The O-g-C3N4 showed excellent photocatalytic activity.•·O2- was the main reactive oxidative species in the photocatalytic degradation.•The photocatalytic reaction mechanism was proposed. [Display omitted] Graphitic carbon nitride (g-C3N4) has aroused extensive attention as a promising candidate for metal-free photocatalysts but is oppressed by its limited photocatalytic efficiency because of the rapid recombination of photogenerated carriers, finite actual reactive sites and poor optical absorption. Doping modification as well as constructing two-dimensional layered structure of g-C3N4 are widely used as effective strategies to improve photocatalytic performance. However, the present synthesis methods still need to improve. In this work, we report a facile hydrogen peroxide assisted hydrothermal approach to synthesize layered oxygen-doped g-C3N4 for photocatalytic degradation of RhB. The obtained samples were investigated in detail by a series of characterization methods. Compared with bulk g-C3N4, the as-prepared few-layer oxygen-doped g-C3N4 sample has modulated CB and VB potentials, lower band gap energy, larger specific surface area, and higher separation efficiency of charge carriers. The photocatalytic RhB degradation constant over few-layer oxygen-doped g-C3N4 is approximately 5-fold higher than that of bulk g-C3N4 counterpart. Finally, an enhanced photocatalytic RhB degradation mechanism was proposed.