Constructing 3D hierarchical TiO microspheres with enhanced mass diffusion for efficient glucose photoreforming under modulated reaction conditions.

Three-dimensional (3D) TiO hierarchical microspheres (THMs) were successfully prepared via a facial template-free hydrothermal approach. The possible growth mechanism of THM was also investigated by TiCl concentration-, time-, and temperature-dependent experiments. The results indicate that the formation of an urchin-like hierarchical structure may follow a "nucleation-dissolution and recrystallization-assembly" process. THM was employed for photoreforming under various catalyst and glucose concentrations, solvent compositions, and pH values. The H production rate, glucose conversion, arabinose and formic acid selectivity reached 9.44 mmol gh, 86.35%, 11.32%, and 46.87%, respectively, under the modulated condition with Pt as cocatalyst; this is attributed to the enhanced mass diffusion caused by the 3D hierarchical morphology as well as the interaction between unsaturated Ti atoms (or oxygen vacancies) in THM and the hydroxyl oxygen atoms on glucose. In addition, the enhanced light absorption induced by defects also exerts a positive effect. In this work, we present an emerging sustainable strategy for the coproduction of H and value-added chemicals from biomass-based glucose with economic photocatalysts under mild conditions.