Effect of mixed Mo/W polyoxometalate modification on photoelectrocatalytic activity of CdS nanocrystals for arsenic(III) oxidation

Modification of semiconductor materials by polyoxometalates (POMs) is a promising strategy for increasing their photoelectrocatalytic (PEC) activity. In this work, we synthesized POM-modified CdS composite nanocrystals based on three kinds of Keggin-type mixed-addendum Mo/W POMs (Ag3PMo3W9O40, Ag3PMo6W6O40, and Ag3PMo9W3O40). This is the first report on the semiconductor properties of the three Keggin-type mixedaddendum Mo/W POMs. Their PEC performances were studied by transient photocurrent responses, electrochemical impedance spectroscopy, and PEC oxidation of As(III) to As(V). The PEC performances of POM-modified CdS composite nanocrystals (CdS/Ag3PMo3W9O40, CdS/Ag3PMo6W6O40, and CdS/Ag3PMo9W3O40) were superior to the performance of pure CdS nanocrystals. CdS/Ag3PMo9W3O40 composite nanocrystals exhibited the highest efficiency for the PEC oxidation of As(III) to As(V), which was about 85% higher than that of the pure CdS nanocrystals. The present study provides insight into developing novel composite nanocrystals with Keggin-type mixed Mo/W POMs for efficient PEC oxidation.