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 °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 ∼700 nm possess a relatively high surface area of ∼80 m2 g−1, large pore size and pore volume of ∼12 nm and ∼0.20 cm3 g−1, respectively. The diameters and wall thicknesses are controllable from ∼500 nm to 1 μm and ∼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 μmol h−1 0.1 g−1), which is two times as high as that of black TiO2 nanoparticles (118 μmol h−1 0.1 g−1) and almost three times that of pristine mesoporous TiO2 hollow spheres (81 μmol h−1 0.1 g−1), respectively.
- This article is part of the themed collection: JMC A Editor’s choice collection: Recent advances in solar fuels and photocatalysis research