Fluorine and tin co-doping synergistically improves the photoelectrochemical water oxidation performance of TiO2 nanorod arrays by enhancing the ultraviolet light conversion efficiency

Abstract

Fluorine and tin co-doped rutile TiO₂ nanorod arrays are grown on fluorine-doped tin oxide substrates by a hydrothermal process and are used as photoanodes to perform photoelectrochemical water oxidation. Fluorine and tin co-doping synergistically enhances the ultraviolet light conversion efficiency of the resulting TiO₂, which enables its photocurrent density of photoelectrochemical water oxidation to be more than four times that of the undoped samples. Such improvement in photoelectrochemical performance is attributed to changes in the electronic structure of the rutile TiO₂ due to fluorine and tin co-doping. It is found that introducing tin into the matrix of rutile TiO₂ can improve the charge separation efficiency because of the enhanced migration of photogenerated electrons from the conduction band of TiO₂ to that of SnO₂ that occurs at local sites, while fluorine doping can greatly reduce the recombination of the photogenerated electron–hole pairs due to the presence of the Ti³⁺ state that is produced to compensate for the charge difference between F⁻ ions and O²⁻ ions. It is envisaged that the fluorine and tin co-doped TiO₂ nanorod arrays described will provide valuable platforms for wide photocatalytic applications that are not merely limited to photoelectrochemical water oxidation.