Engineering electrode/electrolyte interface charge transfer of a TiO2−x photoanode with enriched surface oxygen vacancies for efficient water splitting

Abstract

Oxygen vacancy engineering is one of the most effective strategies for enhancing photoelectrochemical (PEC) performance. In this work, an efficient TiO_2−x nanofiber photoanode based on the thermal reduction of ethylene glycol (EG) was prepared and inhibited charge recombination by confining oxygen vacancies (O_V) at the surface of the TiO₂ photoanode. The optimized TiO_2−x@160 °C nanofiber photoanode with enriched surface O_V achieves a high water oxidation photocurrent of 1.08 mA cm⁻² at 1.23 V vs. RHE, with an outstanding surface charge separation efficiency of 78% and super photostability at 92% over 2000 s. Electrochemical analysis confirmed that the enhanced PEC performance was ascribed to the introduced O_v on the electrode surface, which acted as interband states to trapped photogenerated holes and facilitated the electrode/electrolyte interface charge transfer. Density functional theory calculations indicated that the TiO_2−x with enriched surface O_V lowered the overpotential for accelerating water splitting reaction kinetics on the TiO_2−x surface. This work demonstrated an approach that could be expanded to other electrode materials with tuned surface defects.