Template-free preparation of macro/mesoporous g-C 3 N 4 /TiO 2 heterojunction photocatalysts with enhanced visible light photocatalytic activity

Mesoporous photocatalytic materials with macroporous structures have attracted more and more attention because of their textural mesopores and intrinsic interconnected pore networks, which are able to efficiently transport guest species to framework binding sites. In this work, macro/mesoporous g-C3N4/TiO2 heterojunction photocatalysts were fabricated without templates or additives by a facile calcination method using tetrabutyl titanate and melamine as the feedstocks. Photocatalytic experiments of the as-prepared samples were measured by the photocatalytic oxidation degradation of RhB solution at room temperature under visible light irradiation. The results indicated that the melamine content in the precursors had an important influence on photocatalytic activity of the as-prepared samples. At the optimal loading content, the apparent reaction rate constant (k) was 47.8 × 10−3 min−1 for RhB degradation, exceeding that of pure TiO2 (6.6 × 10−3 min−1) and g-C3N4 (15.2 × 10−3 min−1) by factor of 7.2 and 3.1 respectively. The improved photocatalytic activity was attributed to high surface area and heterostructure formation of g-C3N4/TiO2 composites. The trapping experiment results showed that O2− and h+ were main active species in the decomposition of RhB. A possible enhanced photocatalytic mechanism of g-C3N4/TiO2 heterojunction photocatalysts was proposed.