Tailoring Surface Oxygen Vacancies in Rutile Tio2 by Electrochemical Reduction for Enhanced Photoelectrochemical Performance

Abstract

TiO2 shows great potential in the field of photoelectrochemical (PEC) water splitting. However, the intrinsic drawbacks of TiO2, i.e., the broad band gap and the rapid recombination of charge carriers, significantly limit its PEC performance. Self-doping by oxygen vacancies and Ti3+ has been proved to be an effective means to improve the PEC performance of TiO2. In this work, TiO2 nanowires arrays (TNWs) are synthesized by a modified solvothermal method and the amount of defects Ti3+ and oxygen vacancies was optimized by electrochemical reduction (ER). The reduced TNWs photoanode shows a significantly higher photocurrent density of about 1.5 mA cm-2 at 1.23 V vs. relative hydrogen electrode (RHE), which is 15 times that of pristine TNWs. The enhancement can be ascribed to the promoted light absorption of TNWs and enhanced transport and separation efficiency of photogenerated charge carriers due to the formation of oxygen vacancies induced by ER. Further, the influence of pH of electrolyte and surface structure on the ER of TiO2 are investigated systematically. The experimental results show that R-TNWs with an appropriate amount of oxygen vacancy on the surface prepared at -0.5 V vs. RHE in alkaline environment for 10 min has the highest photocurrent density.

Keywords: rutile TiO2, electrochemical reduction, oxygen vacancies, photoelectrochemical water splitting