Ultra-fast green synthesis of a defective TiO2 photocatalyst towards hydrogen production

Abstract

An ultra-fast green synthesis of defective titanium dioxide (TiO₂) 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 (H₂) production was explored. The obtained TiO₂ 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 TiO₂ NPs with a high generation of Ti³⁺ defects and oxygen vacancies (O_v), 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 H₂ production. Under fluorescence illumination, the sample synthesized with a TiO₂ and L-As weight ratio of 1 : 0.25 (PAs0.25) exhibited the highest H₂ production rate (∼162 μmol g⁻¹ h⁻¹ 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 TiO₂ NPs using an eco-friendly chemical precursor under non-severe conditions.