Self-assembly synthesis of petal-like Cl-doped g-C3N4 nanosheets with tunable band structure for enhanced photocatalytic activity

Boosting the photocatalytic activation of molecular oxygen and photodegradation of tetracycline: The role of interfacial synergistic effect of cocatalyst and dopants

Utilizing reactive oxygen species (ROS), which are generated by the activation of molecular oxygen (O₂) in oxidation reaction, is a promising method for pollutant degradation. However, it is limited by the commonly low efficiency of O₂ activation and carrier separation. Herein, as a model system, Ag cocatalyst and Cl doping modified g-C₃N₄ (Ag/Cl-CN) was constructed to improve the ability of O₂ activation. Results showed that Ag/Cl-CN could effectively convert more O₂ into ROS than pristine g-C₃N₄ (CN), and individually decorated CN (Ag-CN and Cl-CN). A series of experiments and DFT calculations revealed that the deposition of Ag could promote charge separation resulting in more charges accumulated around O₂ and the introduction of Cl led to a stronger adsorption capacity for O₂. Therefore, due to the synergistic effect of Ag cocatalyst and Cl dopant, Ag/Cl-CN generated higher concentrations of O₂^- and displayed much better activity for photocatalytic degradation of tetracycline (TC) than CN, Ag-CN and Cl-CN.

Efficient bacterial inactivation with S-doped g-C3N4 nanosheets under visible light irradiation

The pathogenic bacteria in water that threatens the human health and photocatalytic disinfection have been proven to be a cost-effective and promising green technology. It is significant and necessary to develop efficient, safe, and visible light-driven photocatalysts. In this study, Escherichia coli was used as model bacterium and the disinfection performance of prepared S-doped g-C₃N₄ nanosheets (S-CNNs) under visible light was investigated. The results showed that the synergistic effects of S doping and the unique 2D structure of S-CNNs enhanced the visible light absorption, enlarged the specific surface area and reduced the recombination of photogenerated charge carriers which is beneficial for promoting the photocatalytic disinfection of the E. coli. Scavenger experiments indicated •O₂^- and h⁺ were the predominant reactive species in the photocatalytic disinfection process. In addition, the kinetics of disinfection activity were fitted by the modified Hom model and the k₂ value of S-CNNs is 0.0219 min^-1, which is much higher than that of the bulk g-C₃N₄ (CN). This work has demonstrated efficient bacterial inactivation with S-CNNs under visible light irradiation.

g-C3N4 Sensitized by an Indoline Dye for Photocatalytic H2 Evolution

Protonated g-C3N4 (pCN) formed by treating bulk g-C3N4 with an aqueous HCl solution was modified with D149 dye, i.e., 5-[[4[4-(2,2-diphenylethenyl) phenyl]-1,2,3,3a,4,8b-hexahydrocyclopent[b]indol-7-yl] methylene]-2-(3-ethyl-4-oxo-2-thioxo-5-thiazolidinylidene)-4-oxo-thiazolidin-2-ylidenerhodanine, for photocatalytic water splitting (using Pt as a co-catalyst). The D149/pCN-Pt composite showed a much higher rate (2138.2 µmol·h−1·g−1) of H2 production than pCN-Pt (657.0 µmol·h−1·g−1). Through relevant characterization, the significantly high activity of D149/pCN-Pt was linked to improved absorption of visible light, accelerated electron transfer, and more efficient separation of charge carriers. The presence of both D149 and Pt was found to be important for these factors. A mechanism was proposed.

Growth of narrow-bandgap Cl-doped carbon nitride nanofibers on carbon nitride nanosheets for high-efficiency photocatalytic H2O2 generation

Heterojunction construction has been proved to be an effective way to enhance photocatalysis performance. In this work, Cl-doped carbon nitride nanofibers (Cl–CNF) with broadband light harvesting capacity were in situ grown on carbon nitride nanosheets (CNS) by a facile hydrothermal method to construct a type II heterojunction. Benefiting from the joint effect of the improved charge carriers separation efficiency and a broadened visible light absorption range, the optimal heterostructure of Cl–CNF/CNS exhibits a H₂O₂ evolution rate of 247.5 μmol g⁻¹ h⁻¹ under visible light irradiation, which is 3.4 and 3.1 times as much as those of Cl–CNF (72.2 μmol g⁻¹ h⁻¹) and CNS (80.2 μmol g⁻¹ h⁻¹), respectively. Particularly, the heterojunction nanostructure displays an apparent quantum efficiency of 23.67% at 420 nm. Photoluminescence spectra and photocurrent measurements both verified the enhanced charge carriers separation ability. Our work provides a green and environmentally friendly strategy for H₂O₂ production by elaborate nanostructure design.

The Cl-CNF/CNS heterostructure can efficiently boost the photocatalytic H₂O₂ generation activity.