Double Type-II Heterojunction MnS/Mn–Cd–S/Ni-Polyoxometalate for Improving Visible-Light-Driven H₂ Production

Abstract

Element doping and collaboration with other cocatalysts are two vital strategies to improve the photoelectrochemical properties and overcome the drawbacks of CdS for better photocatalytic performance. In this work, a series of manganese cadmium sulfides (MnxCd1–xS) were obtained by a solvothermal method. When x is equal to or greater than 0.3, MnxCd1–xS is composed of Mn–Cd–S sosoloid and MnS. Among all these MnxCd1–xS products, the Mn0.5Cd0.5S sample showed the best photocatalytic hydrogen production (5.99 mmol g–1 h–1). To further elevate the hydrogen production rate of Mn0.5Cd0.5S, four kinds of Ni-POMs were coupled with it as cocatalysts, and all these composite photocatalysts displayed enhanced performance. The highest efficiency was observed for 15-Ni4–Mn0.5Cd0.5S, which is up to 36.58 mmol g–1 h–1. Various characterizations indicated that Ni4P2W18, Mn–Cd–S sosoloid and MnS in the 15-Ni4–Mn0.5Cd0.5S composite form a double type-II heterojunction, which facilitates the separation and transfer of photogenerated carriers.