Ultra-fast green synthesis of a defective TiO photocatalyst towards hydrogen production.

An ultra-fast green synthesis of defective titanium dioxide (TiO) photocatalysts was conducted by the microwave-assisted method using l-ascorbic acid (l-As) as a reducing agent. Effect of l-As concentrations on the chemical-, optical- and photoelectrochemical properties as well as the photocatalytic performance towards the hydrogen (H) production was explored. The obtained TiO nanoparticles (NPs) illustrated the brown fine powders with different brownness levels depending on the concentrations of l-As. A high l-As concentration provided a high brownness of TiO NPs with a high generation of Ti defects and oxygen vacancies (O), which can extend the light absorption towards the visible and near-infrared regions, suppress the recombination rate of electron-hole pairs, promote the photocurrent response and minimize the interface charge transfer resistance. An appropriate quantity of generated defects and good porous properties played a crucial role in photocatalytic H production. Under fluorescence illumination, the sample synthesized with a TiO and l-As weight ratio of 1 : 0.25 (PAs0.25) exhibited the highest H production rate (∼162 μmol g h in the presence of 1 wt% Au co-catalyst) with a slight drop (∼8.2%) after the 5th use (15 h). The synthesis method proposed in this work provides a new insight to an ultra-fast synthesis of defective TiO NPs using an eco-friendly chemical precursor under non-severe conditions.