Green synthesis of rectangular hollow tubular carbon nitride via in-situ self-assembly strategy to enhance the degradation of tetracycline hydrochloride under visible light irradiation.

It has been an urgent requirement for materials with remarkable performance in the photocatalytic degradation of organic contaminants by photocatalytic technology. Limited surface area and speedy recombination rate of photogenerated charge carriers seriously restrain the application of g-C3N4. Morphology control is a powerful approach to enhance the photocatalytic efficiency of g-C3N4. Herein, we reported a method to attain graphitic carbon nitride with rectangular hollow tubular morphology and asperous surface (TUM-CN-2) which is prepared from urea-melamine hydrothermal products and trithiocyanuric acid by self-assembling without using organic solvents or template agents. The specific surface area, photocatalytic activity, and photo-generated carriers migration and separation rate of the obtained photocatalyst TUM-CN-2 are vastly improved. Contrasted with pure g-C3N4, the degradation rate of tetracycline hydrochloride (TCH) and Rhodamine B (RhB) was enhanced about 3.04 and 13.96 times in visible light irradiation, respectively. Moreover, the interference parameters, active free radicals, potential degradation mechanism, and degradation paths of TCH were researched systematically. This work provides a green way to acquire the modified g-C3N4 with splendid catalytic activity through the self-assembly method.

Synthesis of Double Defects in g-C3 N4 to Enhance the H2 O2 Production by Dual-Electron O2 Reduction.

In this work, the graphitic carbon nitride with -C≡N defects and S-defects (N2 -SCN-4) was constructed. The H2 O2 production efficiency of N2 -SCN-4 was 1423.3 µmol g-1 h-1 under the visible light (λ≥420 nm) irradiation, which was 15.4 times that of pristine g-C3 N4 . The -C≡N groups promote the adsorption of H+ and the S-defects provide the active center for the adsorption and activation of O2 . Furthermore, the surface morphology, microstructure, and photoelectric chemical properties of samples were investigated by a series of characterizations, and the response range of N2 -SCN-4 to visible light increases obviously. Meanwhile, the efficiency of photo-produced charge separation and the selectivity of H2 O2 production were discussed in detail. The experimental and characterization results confirmed that the charge separation efficiency and the selectivity of the 2e- O2 reduction reaction (ORR) were improved under the synergistic effect of the double defects. This work provides a strategy for improving the photocatalytic performance of photocatalysts.