The poor selectivity and activity of the photocatalysts developed has hindered the photocatalytic production of hydrogen peroxide (H 2 O 2 ). Therefore, modification techniques need to be pursued to improve the selectivity and activity of photocatalysts toward the two-electron oxygen reduction reaction. In this study, homogeneous self-modification by nitrogen vacancies is adopted as an efficient technique to narrow the band gap and induce the midgap states in the nanostructures of g-C 3 N 4 synthesized by cyanuric acid−melamine supramolecular adducts. The presence of the vacancies in the structure and their respective effects on the optoelectronic features of the catalysts were thoroughly investigated by different characterizations. The optimized photocatalyst showed greatly improved H 2 O 2 production of 200 μM under 1 h visible light irradiation, as compared with that of the bulk (35 μM) and the pristine nanostructured sample (85 μM), with acceptable reusability. This study also provides a new perspective on devising synergistic approaches to modify the performance of supramolecular-based carbon nitride photocatalysts.

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Zinc sulfide is a UV-active photocatalyst and it undergoes photocorrosion under light irradiation. In this work, the defect sites on ZnS nanoparticles (NPs) surfaces were induced with the help of powerful ultrasonic waves. The defect sites caused (1) suppression of photocorrosion in a large extent under UV light irradiation and (2) enhancement of visible light photo activity. The photocorrosion inhibition was induced by raising valence band (VB) position through the formation of interstitial zinc and sulfur vacancy states in the ZnS band structure and weakening of oxidative capacity of hole. The enhancement of visible light photocatalytic activity may be related to the generation of more defect energy states in the ZnS band gap. Under visible light irradiation, the electron was excited from the ZnS VB to the interstitial sulfur and zinc vacancy states before injecting into the conduction band of ZnS. Therefore, we modified the band gap of ZnS so that it acts as a visible light active photocatalyst. ZnS NPs were prepared using two different classical and ultrasound methods. The prepared ZnS using ultrasound method, exhibited more outstanding photocatalytic activity for degrading reactive black 5 (RB5) under UV and sunlight irradiation in comparison with the classical method. Details of the degradation mechanism under UV light were investigated. This work provides new insights to understanding the photocorrosion stability and visible light activity of bare ZnS photocatalyst.

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In this work, we present the in situ exfoliation of graphitic carbon nitride (g-C 3 N 4 ), engineering holey defects on 2D g-C 3 N 4 layers, and formation of self-assembled graphene via solvothermal treatment of g-C 3 N 4 -bulk in various organic solvents. Methyl alcohol, isopropyl alcohol, tetrahydrofuran, and dimethylformamide were chosen for exfoliating and modifying g-C 3 N 4 sheets based on their compatibility with g-C 3 N 4 in Hansen parameters. Uniform holey defects on 2D g-C 3 N 4 nanosheets were successfully engineered using tetrahydrofuran solvent in a facile solvothermal process. The introduction of N vacancies in heptazine units and the formation of the holey structure of tetrahydrofuran-modified g-C 3 N 4 sample (C 3 N 4 -THF) led to high photocatalytic performance due to enhanced mass transfer, shortening of the charge diffusion lengths, and increased charge separation during the photocatalysis process. Furthermore, full exfoliation of the engineered nanostructure of holey defect C 3 N 4 -THF into a monolayer in reaction media led to maximizing accessible reducing and oxidizing active sites. As a result, the C 3 N 4 -THF sample achieved photocatalytic activity with a H 2 evolution rate at stationary point as high as 31256.9 μmol h −1 g −1 under 1 Sun illumination of a solar simulator.

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