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In this study, a novel BiOBr/HPW/Au photocatalyst was prepared via hydrothermal method followed by photo-reduction method. The characterization results indicated the successful introduction of HPW and Au in BiOBr. BiOBr/HPW/Au exhibited excellent photocatalytic activity in RhB degradation. The degradation rate constant of BiOBr/HPW/Au was 3.55 times higher than that of BiOBr. Radical scavenger experiments showed that ·O−2 was the dominant reactive radical species. A possible mechanism of the enhanced photocatalytic activity was attributed to the synergistic effect of BiOBr, HPW and Au, which resulted in enhanced quantum efficiency and high light harvesting efficiency.

A novel ternary Au NPs/g-C3N4/BiOBr Z-scheme heterojunction composite was fabricated through hydrothermal and in-situ reduction method, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible diffuse reflection spectroscopy and photoluminescence emission spectroscopy. The photocatalytic activity was evaluated by the degradation of phenol under visible-light irradiation. It was found that Au NPs/g-C3N4/BiOBr showed enhanced photocatalytic activity, which is 3-fold higher than g-C3N4 and 2.5-fold higher than BiOBr. This could be attributed to the effective separation of photogenerated electron-hole pairs, narrowed band gap (2.10 eV) and surface plasmon resonance (SPR).

A series of bismuth oxybromide photocatalysts were fabricated via a one-step hydrothermal method through pH value adjustment. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic activities of the as-prepared samples were examined by degradation of Rhodamine B (RhB), methyl orange (MO) and phenol. The results indicate that the B9 displayed the highest photocatalytic activities. The enhanced photocatalytic activity can be attribute to enhanced absorption in the visible region and the decreased recombination efficiency of photogenerated charge carriers. The effect of hydrothermal pH value on the composition and morphology was explored and a synthesis process of bismuth oxybromide was proposed.

Various graphitic carbon nitride (g-C3N4) materials having nitrogen defects were synthesized by adding NaHCO3 during the thermal polymerization of melamine. The as-prepared g-C3N4 samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-visual diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PL); their photocatalytic activity in the degradation of Rhodamine B (RhB) under visible light irradiation was investigated. The results demonstrated that the unique nitrogen defects in g-C3N4 play an important role in broadening the absorption of visible light and enhancing the separation of electron-hole pairs. The photocatalytic activity of g-C3N4 with nitrogen defects is enhanced greatly; the RhB removal rates over the CNK0.005, CNK0.01, and CNK0.05 photocatalysts in 30 min reach 79.8%, 100.0% and 87.6%, respectively. In contrast, the pristine g-C3N4 free of nitrogen defects only gives an RhB degradation rate of 59.8% under the same reaction conditions.

Ultralight and nitrogen doped graphene aerogels (UNGAS) are developed by a hydrothermal method in the presence of graphene, dopamine (DA) and L-arginine. Analysis shows that DA can functionalize the graphene surface and also embed nitrogen atoms onto the graphene sheets upon pyrolysis, and the values of pH on the hydrothermal fabrication of UNGAS have great influence on the formation of UNGAS. By adjusting the amount of L-arginine and dopamine in the precursor mixture, UNGAS with a density as low as 2.54 mg/cm3 can be prepared. The UNGAS show high absorption capacity for various oils due to low density, N doping and large surface area.