Mesoporous black TiO hollow shells with controlled cavity size for enhanced visible light photocatalysis.

Black TiO formed by introducing lattice disorder into pristine TiO has a narrowed band gap and suppresses the recombination of charge carriers. This provides a potential strategy for visible light photocatalysis. However, the microstructural design of black TiO for a higher optimization of visible light is still in high demand. In this work, we proposed the preparation of black TiO hollow shells with controllable cavity diameters using silica spheres as templates for the cavities and the NaBH reduction method. The decreased cavity size resulted in a hollow shell with an enhanced visible-light absorption and improved photocatalytic performance. Moreover, we demonstrated that this cavity can be combined with gold nanoparticles (AuNPs) to form AuNPs@black TiO yolk-shells. The AuNPs provided additional visible light absorption and promoted the separation of photogenerated carriers in the yolk-shell structures. This further improved the photocatalysis, the degradation rate of Cr(VI) can reach 0.066 min. Our work evaluated the effect of the cavity size on the photocatalytic performance of hollow and yolk-shell structures and provided concepts for the further enhancement of visible-light photocatalysis.