Objective Aiming at problems in the field of photodegradation, such as low mass transfer efficiency of a single catalyst, easy recombination of photogenerated carriers, limited light absorption performance and reaction active site, and poor reusability, a self-assembly method was used to construct a g-C3N4/MXene/Ag3PO4 S-type heterojunction catalyst structure, attempting to dope catalyst into polyacrylonitrile ( PAN) spinning solution. The g- C3N4/MXene/Ag3PO4/PAN composite nanofiber membranes were successfully prepared using electrospinning technology. Method In order to further characterize the morphology and structure of the composite nanofiber membrane, we used scanning electron microscopy, transmission electron microscope, infrared spectroscopy, and X-ray diffraction to characterize the size and morphology of the nanofiber membrane and its photocatalytic degradation performance for specific dyes. We also investigated its photocatalytic degradation performance for dye wastewater such as Reactive Red 195 in order to further explore its practical application potential. SEM and TEM characterization analysis showed that when photocatalysts were added, the nanofibers changed from a uniform long straight fibrous structure to a curved network structure. Results The morphology of the nanofibers in the PAN composite nanofiber membrane was better, and g - C3N4/MXene/Ag3PO4 could be loaded onto the PAN through electrospinning technology. The g-C3N4/MXene/ Ag3PO4 could be uniformly distributed on the surface of the composite nanofiber membrane. The diameter before and after loading g-C3N4/MXene/Ag3PO4 on the fibers showed a uniform state, with a size of approximately 200- 400 nm. To investigate the specific impact effects, a composite nanofiber membrane was used for photocatalytic degradation of 50 mL of Reactive Red 195 (0.05 mmol/L) solution. The experimental results showed that the degradation rate of g - C3N4/MXene/Ag3PO4 gradually increased with time, and the dye was almost completely degraded after 60 min. This fully demonstrated the very important role of g - C3N4/MXene/Ag3PO4 in the degradation of Reactive Red 195 dye. In addition, although the degradation rate of dyes by g - C3N4/MXene/ Ag3PO4/PAN was slow in the early stage of the reaction, the dyes were almost completely degraded at 180 min, indicating that the composite nanofiber membrane showed the same degradation effect as g-C3N4/MXene/Ag3PO4 and still had good photocatalytic degradation performance for dyes. After 180 min, the photocatalytic activity of g- C3N4/MXene/Ag3PO4/PAN composite nanofiber membrane was still high, with a degradation rate of 91. 23%, exhibiting good recyclability. The g-C3N4/MXene/Ag3PO4/PAN still had a high decolorization rate for Reactive Red 195 after 5 cycles of used. The degradation rates of Reactive Red 195 were 91.23%, 82. 54%, 81.40%, 79.30%, and 77. 11% after 5 cycles of reaction for 180 min, respectively, indicating that g - C3N4/MXene/ Ag3PO4/PAN had good reusability and stability. Exploring the photocatalytic mechanism of g - C3N4/MXene/ Ag3PO4 catalyst, it was found through radical quenching experiments that superoxide radicals • O2- and hole h+ were the main active species in the oxidative degradation reaction of dyes. After adding tert-butanol, disodium ethylenediaminetetraacetic acid, and p-benzoquinone to the reaction system, the degradation rates of Reactive Red 195 were 86. 15%, 42. 31%, and 10. 82% at 180 min, respectively. This indicated that in the g-C3N4/MXene/ Ag3PO4/PAN system, the contributions of • OH, h+ and • O2- to the decolorization and degradation reactions of dyes were 5.05%, 48. 89%, and 80.38%, respectively. The • O2- and h+ were the main active species in the oxidative degradation reactions of dyes. Conclusion It was proposed that the mechanism of photocatalytic oxidation degradation of dyes may be the formation of a reasonable S-type heterojunction in g-C3N4/MXene/Ag3PO4. The introduction of MXene with high conductivity as a solid-state electron mediator leads to faster electron transfer from Ag3PO4 to the surface of g- C3N4, resulting in higher catalytic performance of the catalyst. This S-type heterostructure provides stronger reduction/oxidation ability to generate more active free radicals and higher catalytic activity to degrade pollutants, thereby decomposing Reactive Red 195 into small molecules under the synergistic effect of • O2- and h+ © 2023 China Textile Engineering Society. All rights reserved.
