Deep desulfurization and denitrogenation of diesel fuel over Ir/Pr-N-CQDs-TiO2 under ultraviolet radiation

[Display omitted] •Defective Ir/Pr-N-CQDs-TiO2 with surface oxygen vacancy and Ti3+ is fabricated.•It extends the photoresponse to visible light region.•The doping of Ir, Pr, N, and CQDs offers adequate surface active sites.•It has excellent consistency for desulfurization and denitrogenation.•It shows excellent efficiency of desulfurization and denitrogenation aided by visible light. Designing an efficient and environmentally-friendly catalyst for desulfurization and denitrogenation of diesel to substitute for widely used catalysts is essential. We have prepared Ir/Pr-N-CQDs-TiO2 by doping N, CQDs, Ir, and Pr in TiO2. The results suggested that turnover frequencies were much higher than those of the others, which indicated that the prepared catalyst had an excellent activity of desulfurization and denitrogenation under ultraviolet radiation. Turnover frequencies of benzothiophene, dibenzothiophene, and 4, 6-dimethyldibenzothiophene were 62.8, 78.4, and 92.4, and turnover frequencies of quinolone, indole, and carbazole were 64.5, 88.4, and 86.5, respectively. The ratios of desulfurization and denitrogenation reached 99.8% and 95.5%. The results of PL, UV–vis, and EPR showed the doping of N, CQDs, Ir, and Pr could extend the range of photo-absorption and improve the hole-electron separation of TiO2. This might be because of the N, CQDs, Ir, and Pr increasing oxygen vacancies and defects on the catalytic surface, forming lower gap energy and rapidly transferring and reserving electrons under ultraviolet radiation. Also, the photocatalytic mechanism of Ir/Pr-N-CQDs-TiO2 was proposed in the present work.