Nitrate-group-grafting-induced assembly of rutile TiO2 nanobundles for enhanced photocatalytic hydrogen evolution

In this study, an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution. Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles. The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4 mu mol h(-1), which is 3.1 times higher than that of Degussa P25-TiO2. It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged, which is favorable for trapping positive protons and improving charge carrier separation, thereby enhancing photocatalytic hydrogen production. Additionally, surface charges were crucial to structural stability based on electrostatic repulsion. This study not only developed a facile surface modification strategy for fabricating efficient H-2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature. (C) 2020, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.