Mesoporous (101)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies for boosting photocatalytic hydrogenation of nitrobenzenes

Abstract

Photocatalytic hydrogenation of nitrobenzenes to anilines has become a rising research hotspot in the field of heterogeneous catalysis; however, its bottleneck is the design of high-activity photocatalysts. In this work, mesoporous (101)-TiO₂ nanocrystals with tailored Ti³⁺ and surface oxygen vacancies have been prepared through a combined facile hydrothermal and post-reduction approach, and exhibit significantly enhanced activity for photocatalytic hydrogenation of nitrobenzenes to anilines in water medium under visible-light irradiation. Experimental results show that the significantly enhanced activity of the prepared photocatalysts is mainly attributed to the strong synergetic effect of the exposed (101) facets, Ti³⁺ self-doping, and surface oxygen vacancies, distinctly resulting in enhanced photoelectron-enrichment on the (101) facet by the accumulated reduction sites, an improved visible-light harvesting ability by energy band gap narrowing, and a boosted photoelectron–hole separation ability by Ti³⁺ and surface oxygen vacancies acting as electron sinks. Meanwhile, a plausible reaction mechanism for photocatalytic hydrogenation of nitrobenzenes to anilines has been proposed and elucidated in detail based on active species capturing experiments. It's expected that this work can stimulate increasing interest in designing high-activity photocatalysts for future green and sustainable organic synthesis.