Phosphate Modulated Nitrogen-doped Titanium Dioxide/ Carbon Nitride Heterogeneous Photocatalysts with Efficient O2 Activation for Ametryn Degradation

Abstract

4P-5NT/CN with high O2 activation and charge separation properties were synthesized by wet chemistry and calcination for photocatalytic degradation of Ametryn (AME). The 4P-5NT/CN nanocomposites with a wide visible light absorption range exhibited excellent charge transfer and separation properties, which significantly improved the photocatalytic degradation of AME by CN photocatalysts.The Z-type charge transfer mechanism between N-doped TiO2 (NT) and g-C3N4 (CN) and the high oxygen adsorption oxygen activation function of surface-modified phosphoric acid were the key to the improved photocatalytic performance. The improved oxygen activation performance further induces the generation of more active species and accelerates the interaction with AME to initiate degradation. The results showed that the photocatalytic degradation of AME by 4P-5NT/CN was 25.8 times higher than that of pure CN under the optimal loading conditions. Oxygen temperature programmed desorption ( O2-TPD ) experiments showed that H3PO4 promoted the physical adsorption of O2 on the surface of the material, effectively facilitating oxygen activation and inducing •O2-. Reactive oxides (ROS) were determined by ESR and free radicals capture detection. The intermediate fragmentation products of AME degradation were detected by liquid chromatography tandem mass spectrometry (LC-MS/MS), and the synergistic degradation pathways of •O2- and •OH were obtained. The synergistic effect is reflected in the fact that •O2- tends to attack the ethyl chain, triggering the degradation reaction, whereas •OH tends to attack the sulfur methyl group, ultimately leading to better mineralisation. This work reveals the selection pattern of AME active sites by ROS during photocatalytic degradation, and provides a new idea for the design of visible-light-driven high-oxygen-activity photocatalysts for the efficient treatment of pollutants in the environment with effective mineralisation.