Influence of g-C3N4 Precursors in g-C3N4/NiTiO3 Composites on Photocatalytic Behavior and the Interconnection between g-C3N4 and NiTiO3

In this study, composite photocatalysts were produced from NiTiO3 and N2-rich precursors (dicyandiamide, melamine, urea, and thiourea) under N2 flow conditions. The goal of the study was to investigate the interaction between NiTiO3 and the synthesized g-C3N4. The properties of the g-C3N4/NiTiO3 (CNT) composites were different depending on the starting materials. Dicyandiamide and thiourea created strong connections with NiTiO3 and resulted in the generation of Ti–N and Ti–O–S bonds. Urea and melamine, however, had difficulty forming g-C3N4 structures or interconnections with NiTiO3. The Ti–N and Ti–O–S bridges in the composite photocatalysts led to increased photocatalytic activity as well as inhibition of the recombination rate. Additionally, the band diagrams of g-C3N4 prepared from dicyandiamide and thiourea exhibited positions suitable for the Z-scheme charge-transfer model with NiTiO3, implying that the composite photocatalysts were applicable for photocatalytic degradation of organic contaminants under the visible-light irradiation. Higher reaction rate constants for the composites prepared with dicyandiamide and thiourea confirmed the significant role of the Ti–N/Ti–O–S bridge between g-C3N4 and NiTiO3.