Facile strategy for controllable synthesis of stable mesoporous black TiO2 hollow spheres with efficient solar-driven photocatalytic hydrogen evolution

Hydrogenated black TiO2 has been proven to tune the bandgap and utilize solar energy effectively. Herein, we report a facile strategy for controllably synthesizing stable mesoporous black TiO2 hollow spheres (MBTHSs) with a narrow bandgap via a template-free solvothermal approach combined with a small amine molecule reflux-encircling process and subsequent high-temperature hydrogenation, which are composed of highly crystalline pore-walls, Ti3+ in frameworks and surface disorders. The encircled protectors especially ethylenediamine result in high thermostability of the TiO2 hollow structures, which not only facilitate hydrogenation (600 degrees C), but also inhibit grain growth and anatase-to-rutile phase transformation as well as retain a high structural integrity. The MBTHSs with a diameter of similar to 700 nm possess a relatively high surface area of similar to 80 m(2) g(-1), large pore size and pore volume of similar to 12 nm and similar to 0.20 cm(3) g(-1), respectively. The diameters and wall thicknesses are controllable from similar to 500 nm to 1 mu m and similar to 35 to 115 nm, respectively. The high crystallinity, integrated hollow structure, Ti3+ in frameworks and surface disorders of the MBTHSs give rise to an extending photoresponse from the ultraviolet to the visible light region and significant improvement in the solar-driven photocatalytic hydrogen evolution rate (241 mu mol h(-1) 0.1 g(-1)), which is two times as high as that of black TiO2 nanoparticles (118 mu mol h(-1) 0.1 g(-1)) and almost three times that of pristine mesoporous TiO2 hollow spheres (81 mmol h(-1) 0.1 g(-1)), respectively.