Selected-atom-regulated C3N4 for enhanced photocatalytic degradation of pesticides

A wide variety of pesticides have been applied for crop protection and become an increasing demand, of which herbicides account for nearly half. Despite the high herbicidal efficiency and low price, herbicide residue is increasingly criticized because of the potential negative impact on the environment and public health. Heterogeneous photocatalysis is an efficient technique to address these issues. Photocatalytic degradation of herbicides has been achieved mainly with TiO₂ or ZnO based semiconductors under UV light irradiation. Featured with visible-light response, non-toxicity, and physicochemical stability, polymeric carbon nitride (PCN) presents great potential for organic pollutants degrading. However, the limitations derived from the inherent recombination of photoexcited electrons and holes limited its photocatalytic performance.

In this work, oxygen atom and single metal atom regulated CN were synthesized and applied for herbicides degradation. The presence of an isolated metal atom was confirmed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculations suggested that Pt_SA-HCNNS with Pt–N₄ coordination and SA-FeN₆/CN with Fe–N₆ is favorable for the formation of ROS. DFT calculations were conducted to gain insights into the catalytic mechanisms. The charge localization caused by the isolated metal atom and the creation of electron-rich regions may facilitate charge-carrier separation and O₂ capture. The main photodegradation products were identified, and the photodegradation pathway of investigated herbicides was proposed. The phytotoxicity of treated herbicide toward soybean seedlings was greatly reduced after the photodegradation.

Dr. Xue Liu currently works at the Institute of Tobacco Research, Chinese Academy of Agricultural Sciences as an associate researcher. She has been dedicated to seeking feasible applications of nano-materials in pesticide residue analysis and environmental remediation. She obtained her PhD degree from China Agricultural University.