Sandwich-type cobalt-polyoxometalate as an effective hole extraction layer for enhancing BiVO4-based photoelectrochemical oxidation

Bismuth vanadate (BiVO4) as an outstanding semiconductor material has been extensively used in visible-light-driven photocatalytic oxidation. However, the fast electron-hole recombination on the surface of BiVO4 photoanode impairs its photoelectrochemical oxidation performance. In this work, we demonstrate, for the first time, that a cobalt-polyoxometalate (Ag-10[Co-4(H2O)(2)(PW9O34)(2)], PW9Co) is exploited as a hole extraction layer on the surface of BiVO4 photoanode for boosting photoelectrochemical activity by promoting hole extraction and transfer. Compared to the pure BiVO4 photoanode, the PW9Co-modified BiVO4 photoanode in photoelectrochemical water oxidation reaction exhibited a higher photocurrent density of 3.06 mA cm(-2) at 1.23 V vs. RHE under AM 1.5G illumination, achieving a 3.3-fold improvement in photocurrent density. Furthermore, we performed a photoelectrochemical reaction of oxidizing benzyl alcohol into benzaldehyde, in which the reaction yield of using the modified BiVO4 photoanode is significantly superior to the pure BiVO4 photoanode. These results prove that a rational selection of cobalt-polyoxometalate as a hole extraction layer can efficiently enhance the photoelectrochemical oxidation activity of BiVO4 photoanode. (C) 2019 Elsevier B.V. All rights reserved.