g-C3N4/TiO2 uniformly distributed microspheres: preparation for enhanced photocatalytic performance by co-calcination

To solve the drawbacks that TiO2 photocatalyst only responds to ultraviolet (UV) light, some surface modification strategies have been proposed. However, most of them were impeded by the tedious preparation method and limited performance enhancement. Herein, a uniformly distributed structure of g-C3N4 nanosheets on the surface of spherical TiO2 particles prepared by co-calcination of urea and TiO2 precursors was verified to effectively solve those problems. The realization of this synthesis process contributed to the high dispersion and reasonable particle size distribution of the composites, which effectively restrained the agglomeration between them. The homogenous heterojunction structure formed after the surface decoration of C3N4 increased the specific surface area of TiO2 from 9.25 to 18.05 m2/g, which could bring sufficient active sites in the photocatalytic reaction process. UV–Vis diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and photochemical tests showed that g-C3N4/TiO2 has strong visible light absorption and photo-generated carriers transfer ability. The photocatalytic degradation rate of g-C3N4/TiO2 reached 98.5% for RhB dye solution within 15 min under the irradiation of sunlight, which is even better than that of P25 TiO2 under the UV light irradiation. This work provided a simple and efficient method for the construction of TiO2 based heterojunction by designing the morphology of the TiO2 precursors and the co-calcination of urea in a proper way.