Exploring the influencing factors of the electrochemical reduction process on the PEC water splitting performance of rutile TiO2

The self-doping of oxygen vacancy and Ti³⁺ by electrochemical reduction (ER) method has been proved to be an effective means to improve the PEC performance of TiO₂. However, the effect of the surface structure on ER treatment remains ambiguous. In this work, three kinds of nanostructured rutile TiO₂ (nanowire arrays (TNWs), etched nanowire arrays (E-TNWs) and nanorod arrays (TNRs)) were reduced electrochemically to explore the factors influencing the ER process of rutile TiO₂. The experimental results show that alkaline environment (1 M NaOH) is more conducive to the occurrence of ER reaction. And the reduced three kinds of nanostructured TiO₂ photoanodes show a significantly higher photocurrent density of about 1.46, 1.65 and 1.45 mA cm⁻² at 1.23 V vs. relative hydrogen electrode (RHE), respectively, which are 15, 16 and 1.1 times that of pristine TiO₂. The different degrees of photocurrent density enhancement can be ascribed to the different degrees of electrochemical reduction of TiO₂ with different crystallinity and exposed crystal facets as well as specific surface area. This study provides new insights into the mechanism of electrochemical reduction method.