β-O-4 linkage breakage of lignin enabled by TiO2 with off/on switchable defect sites for photocatalysis

Hydrogenated titanium dioxide (H–TiO2) was synthesized by using a one-step solvent volatilization method. The Ti–H bonds were formed by hydrogen doping and subsequently oxidized to Ti–O bonds in air atmosphere. In comparison to air atmosphere, using the N2 annealing environment as a switch to promote the formation of oxygen vacancies improved visible light absorption and prolonged carrier recombination time. Furthermore, compared with conventional TiO2 microspheres, the catalytic activity was doubled by breaking the β-O-4 linkage in lignin models. The transformation of lignin into high-value compounds was enabled by TiO2-based photocatalyst under visible light. TiO2 microspheres enriched in oxygen vacancies which make full use of the annealing atmosphere as a switch to control defect engineering were synthesized by using a mild, facile, and efficient process. This work provides a new approach to significantly improve the photocatalytic efficiency for practical applications.