Fluorine doped copper tungsten nanoflakes with enhanced charge separation for efficient photoelectrochemical water oxidation

Abstract

Inefficient electron-hole separation greatly restricts the performance of CuWO4 toward photoelectrochemical oxygen evolution reaction. To address such issue, we developed a facile fluorine doping approach, in which F− anions were incorporated into the crystal lattice of n-type CuWO4 nanoflakes and served as effective electron donors to increase the electron density. The dopant concentration in CuWO4 could be easily controlled by varying the added amount of F precursor solution. The obtained F-doped CuWO4 retained the two-dimensional network structure of the undoped CuWO4 nanoflakes. The obtained F-doped CuWO4 nanoflakes exhibited a highly-enhanced activity and an excellent stability for photoelectrochemical oxygen evolution reaction. The activity of F-doped CuWO4 depended on the F-doping concentration. The 2.50 at.% F-doped CuWO4 showed the highest photocurrent density of 0.57 mA cm−2 at 1.23 V vs. reversible hydrogen electrode, which is ca. 1.8 times that of the pristine CuWO4 (0.32 mA cm−2) and stands among the highest values reported for CuWO4-based photoanode. The high activity of F-doped CuWO4 was ascribed to the significantly-improved electron-hole separation efficiency, which resulted from F-doping induced high electron density in F-doped CuWO4. This work suggests that anion doping is an effective way to further improve the photoactivity of CuWO4 toward photoelectrochemical oxygen evolution reaction.