Controllable Synthesis of Defective TiO₂ Nanorods for Efficient Hydrogen Production

Nanorods (NRs), with their high atomic surface exposure within a crystalline architecture, facilitate effective diffusion/transport of charge, rendering them particularly suitable for applications requiring both interaction with the media and charge transfer. In this study, we present a straightforward approach to produce brookite-phase titanium dioxide (TiO₂) NRs with tunable defects and narrow size distributions by utilizing methylamine hydrochloride and 1,2-hexadecanediol as shape-directing agents. The presence of the Ti³⁺ defect was confirmed by electron paramagnetic resonance and X-ray photoelectron spectroscopy, and its effect on the photocatalytic properties of TiO₂, with and without Pt loading, show that the longest TiO₂ NRs provide the highest photocatalytic and photoelectrochemical hydrogen production activity. Transient photocurrent response analysis, electrochemical impedance spectroscopy, and Mott-Schottky analysis plots indicate that an increase in temperature significantly reduces the interface barrier and lowers the transport resistance, leading to a 104% improvement in hydrogen production rates from 25 to 60 °C for the longest TiO₂ NRs. This study underscores the critical role of the TiO₂ nanorod dimensions (18-45 nm) in elevating the hydrogen production efficiency. At 25 °C, rates surged from 1.6 to 2.6 mmol g^-1 h^-1, and at 60 °C, rates soared from 3.3 to 5.3 mmol g^-1 h^-1, demonstrating the substantial impact of TiO₂ NRs on enhancing hydrogen generation.