Boosting Photosynthetic H2O2 of Polymeric Carbon Nitride by Layer Configuration Regulation and Fluoride-Potassium Double-Site Modification

Defective Poly(heptazine imide) Nanosheets for Efficient One-Step Two-Electron Photocatalytic O2 Reduction to Medical-Like H2O2

Poly(heptazine imide) (PHI) is a promising photocatalyst for hydrogen peroxide (H2O2) production; however, enhancing its specific surface area to expose internal active sites and understanding their roles in key mechanistic steps for the H2O2 synthesis remain challenging. Here, we utilized organic cations to exfoliate bulk PHI and fabricate PHI nanosheets for producing H2O2 at a rate of 27.35 mmol g-1 h-1 under simulated solar light irradiation, outperforming most of the reported carbon nitride-based catalysts. Importantly, after 36 h of cyclic accumulation reactions in a self-created spiral flow reactor, the H2O2 concentration stabilized at 2.7 wt.%, close to medical sterilization levels. In situ spectroscopic characterizations and density functional theory calculations revealed that the exfoliation results in molecular reconfiguration of the PHI basal planes, forming the active sites to promote charge separation and electron localization. This new structure also creates midgap states, enabling direct H2O2 production via a one-step, two-electron pathway, bypassing the superoxide radical pathway. Theoretical calculations suggest that the localized electronic structure created by the active sites favors the protonation of adsorbed O2 and stabilizes the *OOH species, which converts to H2O2. This study elucidates and underscores the importance of active-site reconfiguration for efficient photocatalytic oxygen reduction reaction (ORR) pathways.

Cu Anchored Carbon Nitride (Cu/CN) Catalyzes Selective Oxidation of Thiol by Controlling Reactive Oxygen Species Generation

Production of H2O2 using heterogeneous semiconductor photocatalysts has emerged as an ecofriendly and practical approach across various applications, ranging from environmental detoxification to fuel cells and chemical synthesis. Extensive efforts have been devoted to engineering semiconductors to enhance their catalytic capabilities for H2O2 production. However, in chemical synthesis, the utilization of the potent oxidant H2O2 can present challenges in selectively oxidizing organic compounds. In this study, we introduce copper atoms into carbon nitride (Cu/CN), facilitating the generation of hydroperoxyl radicals (·OOH) as primary reactive oxidants and offering reaction conditions entirely devoid of H2O2 via the Fenton reaction. Cu/CN demonstrates selective oxidation of thiols to disulfides, in contrast to other current heterogeneous photocatalysts that yield undesired overoxidized side products, such as thiosulfinate and thiosulfonate. Cu/CN's controllable capacity for specific ROS generation, broad substrate scopes, and recyclability empower greener and highly selective photooxidation of organic compounds.

Engineering Polyheptazine and Polytriazine Imides for Photocatalysis

As organic semiconductor materials gain increasing prominence in the realm of photocatalysis, two carbon-nitrogen materials, poly (heptazine imide) (PHI) and poly (triazine imide) (PTI), have garnered extensive attention and applications owing to their unique structure properties. This review elaborates on the distinctive physical and chemical features of PHI and PTI, emphasizing their formation mechanisms and the ensuing properties. Furthermore, it elucidates the intricate correlation between the energy band structures and various photocatalytic reactions. Additionally, the review outlines the primary synthetic strategies for constructing PHI and PTI, along with characterization techniques for their identification. It also summarizes the primary strategies for enhancing the photocatalytic performance of PHI and PTI, whose advantages in various photocatalytic applications are discussed. Finally, it highlights the promising prospects and challenges of PHI and PTI as photocatalysts.

ZnS/C Dual-Quantum-Dots Heterostructural Nanofibers for High-Performance Photocatalytic H2O2 Production

Constructing heterostructures of dual quantum-dots (QDs) is a promising way to achieve high performance in photocatalysis, but it still faces substantial synthetic challenges. Herein, we developed an in situ transformation strategy to coassemble ZnS QDs and C QDs into dual-quantum-dot heterostructural nanofibers (ZnS/C-DQDH). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results revealed the formation of strong Zn-O-C bonds at the interface between ZnS QDs and C QDs, improving the separation efficiency of photogenerated charge carriers. The ZnS/C-DQDH demonstrated remarkable photocatalytic activity in H2O2 production, with generation rates of 2896.4 μmol gcat-1 h-1 without sacrificial agents and 9879.3 μmol gcat-1 h-1 with ethanol as the sacrificial agent, significantly higher than the QD counterparts and surpassed state-of-the-art photocatalysts. Moreover, due to the nanofibrous feature, ZnS/C-DQDH demonstrated excellent stability and facile recyclability. This work provides a facile and large scalable method to gain dual-quantum-dot heterostructures and a promising alternative for photocatalytic H2O2 production.

Photocarrier transfer induced by Nδ- → Wδ+ in tungsten trioxide/carbon nitride for dual-path production of hydrogen peroxide towards ciprofloxacin degradation

Photo self-Fenton catalyst is a promising candidate for solar energy conversion and environmental remediation. Here we reported a Tungsten trioxide/carbon nitride (WO3/CN) in which the surficial amino groups on CN are inserted into the WO3 matrix, forming coordinate covalently Nδ- → Wδ+ in construction of an intimate S-scheme heterojunction. The intimantance promotes the transfer of photocarriers under light irradiation. The nanohybrids produced hydrogen peroxide (H2O2) in a rate about 20 times of pristine CN. A dual-path architecture in which H2O2 are produced via hole-water oxidation and electron-oxygen reduction was poposed. It is founded that ciprofloxacin also involved in production of H2O2 by their deprotonation to superoxide anions, and holes and hydroxyl radicals effectively attack the weak sites in skeleton of ciprofloxacin. This work suggests a great significance of strategy in self-producing of H2O2 in utilizing solar energy and molecular oxygen for water, particularly the surface water decontamination.