A comparative study on the photocatalytic performance of modified graphitic carbon nitride (g-C3N4) with non-metals (P, B, S) for aerobic oxidative desulfurization

Oxidative desulfurization (ODS) with mild reaction conditions without the use of any external oxidant agents has been validated as an impressive technique for manufacturing clean fuel oil. Considerable materials have been utilized as ODS catalysts, but are existing and restricted by their high cost and probable other pollution. Graphitic carbon nitride g-C3N4 (gCN) as a heterogeneous photocatalyst has an important place among photocatalysts, because of its unparalleled properties such as narrow bandgap, low expense, facile synthesis, and high oxidation capacity. Still, the low surface area and quick recombination of photogenerated charge carriers reduce its photocatalytic efficiency. According to this study, modified gCN with non-metals such as B, P, and S were synthesized to significantly increase its photocatalytic activity. Identification of the synthesized photocatalysts investigated by analysis such as XRD, FT-IR, SEM, TEM, EDS, BET, PL, UV–vis DRS, XPS, and TGA. The analysis showed that B-gCN and P-gCN samples can absorb better solar energy for two reasons; first, a considerable red shift occurred in the absorption spectrum and second, the band gap was reduced. Already, a blue shift in the band gap of sulfated-gCN shows its smaller structural size that represents the treatment gCN by sulfuric acid decomposed the unstable domains. Hence, the narrow band gap of gCN improved by H2SO4 treatment, and then charge recombination was reduced, and photocatalytic activity increased. Finally, under mild photochemical conditions, a comparative study of these three different reusable photocatalysts containing different nonmetals was performed for the degradation reaction of dibenzothiophene as an important pollutant in the petroleum industry. Among them, under visible light irradiation, room temperature, and oxygen atmosphere sulfated gCN was shown higher efficiency (94 %) and selectivity.