Metal-free photocatalysts with excellent visible-light absorption and highly efficient photocatalytic activity are attractive in the field of photocatalysis owing to their environmental friendliness. Black phosphorus (BP) shows a great potential in photoelectric conversion and photocatalysis due to its tunable band gap and two-dimensional structure. In this work, a stabilized metal-free photocatalyst, reduced graphene oxide (rGO)-wrapped BP heterostructure, was prepared by assembling BP and GO nanosheets in aqueous solution followed by partial reduction and lyophilization. The surface tension of the partially reduced GO during lyophilization could make rGO nanosheets tightly wrap on both surfaces of exfoliated BP nanosheets. This wrapped heterostructure with tight bonding between rGO and BP nanosheets led to a high photocatalytic activity, owing to the rapid transfer of the photogenerated electron−hole pairs at the rGO/BP heterojunction and the high stability of rGO protecting BP from oxygen attack. This work not only provided a general method to prepare the sandwiched heterojunction based on GO with good interface binding capability but also constructed a highly active, stable, metal-free photocatalyst based on BP.

The 3D network structure composed of g-C 3 N 4 nanorods was prepared via treatment of bulk g-C 3 N 4 with hot HNO 3 followed by adjustment the pH and lyophilization. Then the 3D g-C 3 N 4 / TiO 2À x heterojunctions with a strong interface was constructed via loading TiO 2À x nanoparticles onto the 3D g-C 3 N 4 networks under hydrothermal conditions. The structure and morphology of the 3D g-C 3 N 4 /TiO 2À x heterojunctions was characterized by infrared spectrum (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and field emission transmission electron microscope (TEM). The photo-degradation rate of Doxycycline HCl for 3D g-C 3 N 4 /TiO 2À x heterojunction is about 4 times of that original bulk-C 3 N 4 and 2.75 times of 3D g-C 3 N 4. The improved photocatalytic efficiency is attributed to 3D g-C 3 N 4 networks, which provides the more transfer channel to accelerate the electron transportation and the strong heterointerface between g-C 3 N 4 and TiO 2À x which promotes the separation of the electronholes. Besides, more adsorption capacity of the pollutant onto the 3D g-C 3 N 4 /TiO 2À x also contributed to this high efficiency.

The construction of heterojunction between semiconductor is an effective technology to enhance its photocatalytic activity using solar energy. In this paper, a series of BiPO 4 /Bi 2 MoO 6 heterostructures with different mole ratio of Mo:P were successfully synthesized via one-pot solvothermal method. Photocatalytic activity of all samples were investigated by degrading methylene blue (MB) under visible light. Among the catalysts, BMoP-1-3 sample with oxygen vacancy has excellent photocatalytic activity due to improving its light harvesting and charge separation by establishment of Z-scheme system heterostructure, which is 1.65 and 1.22 times that of pure BiPO 4 and Bi 2 MoO 6 , respectively.

N–TiO_2−x nanoparticles (NPs) were selected as a basic construction unit because there are many Ti³⁺ and O vacancies on its surface.

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