Mesoporous black TiO2-x/Ag nanospheres coupled with g-C3N4 nanosheets as 3D/2D ternary heterojunctions visible light photocatalysts.

3D mesoporous black TiO2-x/Ag nanosphere coupled with 2D g-C3N4 sheet ternary heterojunctions are successfully fabricated through a facile evaporation-induced self-assembly (EISA) process and photodeposition method, followed by a mild calcination (350°C) under an argon atmosphere after an in situ solid-state chemical reduction strategy. The resultant mesoporous black TiO2-x/Ag/g-C3N4 ternary heterojunctions with narrow band gap of∼2.27eV possess a relative high specific surface area of∼100m2g-1, main pore size of 6.2nm and the highest visible-light-driven photocatalytic property for degradation of methyl orange (97%) and methylene blue (99%). The apparent reaction rate constants (k) of mesoporous black TiO2-x/Ag/g-C3N4 for methyl orange and methylene blue are∼9 and 11 times higher than that of pristine TiO2. The possible mechanism is proposed, and the excellent photocatalytic property can be ascribed to the introduction of Ti3+ self-doping and g-C3N4, which favor the visible light absorption and the separation of electron-hole pairs, the surface plasma resonance effect of Ag nanoparticle, and the mesoporous networks offer more surface active sites.