Homojunction and defect synergy-mediated electron-hole separation for solar-driven mesoporous rutile/anatase TiO2 microsphere photocatalysts

Abstract

The photocatalytic hydrogen evolution of TiO2 is deemed to be one of the most promising ways of converting solar energy to chemical energy; however, it is a challenge to improve the photo-generated charge separation efficiency and enhance solar utilization. Herein, black mesoporous rutile/anatase TiO2 microspheres with a homojunction and surface defects have been successfully synthesized by an evaporation-induced self-assembly, solvothermal and high-temperature surface hydrogenation method. The H500-BMR/ATM (HX-BMR/ATM, where X means the different hydrogen calcination temperatures) materials not only possess a mesoporous structure and relatively high specific surface area of 39.2 m2 g−1, but also have a narrow bandgap (∼2.87 eV), which could extend the photoresponse to the visible light region. They exhibit high photocatalytic hydrogen production (6.4 mmol h−1 g−1), which is much higher (approximately 1.8 times) than that of pristine mesoporous rutile/anatase TiO2 microspheres (3.58 mmol h−1 g−1). This enhanced photocatalytic hydrogen production property is attributed to the synergistic effect of the homojunction and surface defects in improving efficient electron-hole separation and high utilization of solar light. This work proposes a new approach to improve the performance of photocatalytic hydrogen production and probably offers a new insight into fabricating other high-performance photocatalysts.