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

3D mesoporous black TiO 2-x /Ag nanosphere coupled with 2D g-C 3 N 4 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 TiO 2-x /Ag/g-C 3 N 4 ternary heterojunctions with narrow band gap of   ∼   2.27   eV possess a relative high specific surface area of   ∼   100   m 2   g −1 , main pore size of 6.2   nm 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 TiO 2-x /Ag/g-C 3 N 4 for methyl orange and methylene blue are   ∼   9 and 11 times higher than that of pristine TiO 2 . The possible mechanism is proposed, and the excellent photocatalytic property can be ascribed to the introduction of Ti 3+ self-doping and g-C 3 N 4 , 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.