Degradation of organic dyes in wastewater poses a significant environmental challenge due to their toxicity and resistance to biological factors and traditional treatment methods. Photocatalysis has emerged as a promising solution that uses solar energy to reduce pollutants to harmless substances. This research investigated the efficiency of a TiO2/g-C3N4 heterogeneous structure (where g-C3N4 is present in bulk and exfoliated states before and after doping with boron) as a photocatalyst for dye degradation.The nanohybrid was synthesised through the sol-gel method by in situ growth of titanium dioxide nanoparticles on graphitic carbon nitride structure, followed by characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and Diffuse Reflectance Spectroscopy (DRS). The photocatalytic performance was eva‎luated under visible light irradiation using RhB as a model dye. The results showed that the hybrid TGCNB, which was processed with g-C3N4 in the exfoliated state and doped with boron, shows a superior photocatalytic activity compared to pure TiO2 and boron-doped g-C3N4 (GCNB). The enhanced performance is attributed to the synergistic effects of exfoliation, boron doping, and heterojunction formation between TiO2 and GCNB. Boron effectively reduced the g-C3N4 band gap, but after exfoliation, the band gap increased, resulting in an increase in the specific surface area and the number of active sites. The band gap was increased from 2.65eV to 3 eV by the synergetic effect of these two. Furthermore, the heterostructure contributed to efficient charge separation and decreased the recombination rate of electron-hole pairs. Next, the effect of the percentage of different components of the optimal heterostructure on the rate of photocatalytic activity was investigated, and the heterostructure with a ratio of 50-50 components was introduced as the optimal structure. The degradation efficiency of RhB reached 86% within 160 minutes after irradiation, which is significantly higher than the individual components. To prove that electron-hole pairs in the heterostructure are effectively separated and that they cannot recombine, photoluminescence (PL), electrochemical impedance (EIS), and current density (PC) tests were performed. The degradation process involves hydroxyl radicals (•OH) and superoxide radicals (O2•-), as shown by scavengers. The mechanism of color degradation was proposed based on the changes in the UV-VIS absorption spectrum and RhB's color change during the degradation process. The effective parameters of photocatalytic dye degradation process, such as photocatalyst amount, dye concentration, and optimal pH, were also examined. The TGCNB photocatalyst was assessed for stability and reusability, and there was no significant loss of activity after three cycles. Finally, based on the gained results, the proposed degradation mechanism, and effective reactive oxygen species, the electron transfer mechanism in the heterostructure was introduced as Z type. In conclusion, the heterostructure of TGCNB provides an efficient photocatalyst for the degradation of organic dyes under visible light. This study highlights the potential of non-metallic element doping and heterostructure engineering in enhancing the photocatalytic performance of semiconductor materials.

فتح اله كريم زاده , محمدحسين عنايتي

زهرا طالبي مزرعه شاهي , مهران نحوي