C-doped TiO2/g-C3N4 composites derived from titanium ester-modified precursors with enhanced photocatalytic activity

Using titanium ester Tyzor 371 and dicyandiamide as raw materials, modified precursors DCDA-x were synthesized by hydrothermal method with controlled titanium ester ratios, followed by calcination to prepare TiO 2 -composited C-doped g-C 3 N 4 catalysts TCCN-x. The study shows that hydroxyl groups of the titanium ester form hydrogen bonds with amino groups of dicyandiamide, and their combined steric hindrance suppresses the polymerization of g-C 3 N 4 . Among them, the TCCN-3 precursor exhibits the strongest hydrogen bonding and the most significant inhibition effect. During calcination, the titanium ester decomposes to produce amorphous carbon that integrates into the heptazine rings or interlayers of g-C 3 N 4 , facilitating charge transfer. Simultaneously, the formed TiO 2 creates heterojunctions with g-C 3 N 4 , enhancing carrier separation. Together, these effects synergistically improve the photocatalytic performance. After 60 min of visible-light irradiation, TCCN-3 achieves a methylene blue degradation rate of 53.02%, which is 2.24 times that of pure g-C 3 N 4 (23.60%), exhibiting the best performance. Graphical abstract