Room temperature plasma enriching oxygen vacancies of WO3 nanoflakes for photoelectrochemical water oxidation

Tungsten trioxide (WO3) represents one of the promising materials for photoelectrochemical water oxidation. However, its practical application was still hampered by the sluggish oxygen-evolution kinetics, the rapid recombination of photo-generated charge carriers and the relatively low conductive band level of WO3. Defect control is considered to be one of the promising strategies to improve the water oxidation performance of tungsten oxide photoanodes. In this work, an efficient, room temperature method was developed to enrich oxygen vacancies of WO3 nanoflakes through an Ar plasma treatment for 3 min. The rapid plasma treatment remarkably improved the efficiency of photo-electrochemical water oxidation, where a lower onset potential and higher photocurrent density of 1.20 mA/cm(2) at 1.4 V vs RHE were achieved, twice higher than the photocurrent density of pristine WO3 nanoflakes. The significant improvement was attributed to the enriched edge oxygen vacancies, which increases the donor density of WO3 nanoflakes, almost four times higher than that of the pristine ones, and enhances the electrical conductivity as well as charge transportation. The work represents a rapid, sustainable strategy to perform surface modification of WO3 nanoflakes for enriching the surface oxygen vacancies to improve the photoelectrochemical water splitting, which is very promising to be applied to different materials and a variety of fields. (C) 2019 Elsevier B.V. All rights reserved.