Photocatalytic Oxidation of Glucose into Formate on Nano TiO2 Catalyst

Formic acid, as an excellent hydrogen-storage material, has recently become increasingly important. Previous conversion of biomass into formic acid suffers from problems of strict operation conditions such as the use of a high concentration of H2O2 oxidant and alkali at higher temperatures or the precious metal catalysts. Here, a straightforward photocatalytic method to selectively convert glucose into formate is first reported. Using a nano TiO2 catalyst, we show that glucose can be efficiently converted into formic acid with a high yield of 35% at ambient condition with 0.03 M NaOH concentration, and the proposed method also worked on xylose for formate production. The conversion of glucose into formic acid is mainly attributed to the accelerated formation of active oxidative radicals (O2•–, •OH) in the presence of hydroxyl ions, and also, hydroxyl ions adjust the charge of the TiO2 surface and control the adsorption of glucose and the desorption of formic acid. These results open up a new approach toward economical utilization of sustainable biomass and clean solar energy for formic acid production.