Preparation and activity evaluation of B₄C/ZnO composite photocatalyst

In this study, B₄C/ZnO composite photocatalysts were obtained by the heat treatment of polyvinyl borate composite, synthesized using the crosslinking reaction of polyvinyl alcohol and boric acid in the presence of ZnO nanoparticles. The photocatalytic activity of B₄C/ZnO was evaluated by photocatalytic degradation of a model dye, methylene blue. The relationship between the photocatalytic degradation of methylene blue and the temperature of the reaction medium, and the pH of the reaction medium was also studied. The structural and optical properties of B₄C/ZnO photocatalyst were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) analysis, fluorescence spectroscopy, scanning electron microscopy (SEM), and UV–Vis absorption spectroscopy. The B₄C and B₄C/ZnO composite nanoparticles were synthesized successfully, which was proven by the FTIR, XRD, and SEM analyses. The photocatalytic degradation experiments illustrated that the photocatalytic activity of the composite photocatalysts was higher than that of B₄C on the photocatalytic degradation of the model dye. The heterojunction structure formed between ZnO and B₄C might have decreased the recombination rate, which was determined by the fluorescence spectroscopy. The B₄C/ZnO composites possessed wider optical bandgap compared to pure B₄C, which was determined by Tauc’s plot analysis. When compared with pure B₄C, approximately three times faster degradation rate was obtained by the B₄C/ZnO composite. After four cycles of the photocatalytic degradation experiments, approximately 26% loss in the photocatalytic degradation efficiency was observed. Based on the scavenger experiments to reveal the photocatalytic degradation mechanism, the photoinduced holes, the superoxide radicals, and the hydroxyl radicals were the main active species for the degradation of methylene blue.