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

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 (Mn x Cd 1– x S) were obtained by a solvothermal method. When x is equal to or greater than 0.3, Mn x Cd 1– x S is composed of Mn–Cd–S sosoloid and MnS. Among all these Mn x Cd 1– x S products, the Mn 0.5 Cd 0.5 S sample showed the best photocatalytic hydrogen production (5.99 mmol g –1 h –1 ). To further elevate the hydrogen production rate of Mn 0.5 Cd 0.5 S, 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-Ni 4 –Mn 0.5 Cd 0.5 S, which is up to 36.58 mmol g –1 h –1 . Various characterizations indicated that Ni 4 P 2 W 18, Mn–Cd–S sosoloid and MnS in the 15-Ni 4 –Mn 0.5 Cd 0.5 S composite form a double type-II heterojunction, which facilitates the separation and transfer of photogenerated carriers.