Preparation of hierarchical g-C₃N₄@TiO₂ hollow spheres for enhanced visible-light induced catalytic CO₂ reduction

Hierarchical g-C3N4@TiO2 hollow sphere with excellent photocatalytic activity for CO2 reduction under the visible light was prepared by assembling TiO2 shell onto the surface of hollow carbon nitride sphere (HCNS). This engineered photocatalyst was prepared by a two-step process: at first, the process of nanocasting was done by a templating method, followed by the kinetically-controlled coating technique. Specifically, mesoporous silica sphere and cyanamide were used as sacrificial template and precursor of carbon nitride, respectively, for the synthesis of hollow carbon nitride sphere which was further modified with titanium dioxide nanosheets. The remarkable photocatalytic activity of as-prepared nanocomposite could be attributed to its special structure, providing properties such as light-harvesting, multiple light reflection and enhanced active site. Owing to the synergistic effect between g-C3N4 and TiO2; the light absorption region has been enhanced, leading to the improvement of photocatalytic performance. The obtained CO2 photoreduction efficiency of HCNS@TiO2 nanostructure is 11.3 innol/g(cat).h, which is about 5 and 10 times higher than the corresponding values for pristine gC(3)N(4) and p-25, respectively.