1D/1D W18O49/Cd0.9Zn0.1S S-scheme heterojunction with spatial charge separation for high-yield photocatalytic H2 evolution.

ABSTRACT

Semiconductor photocatalytic water splitting is a green way to convert solar energy into chemical energy, but the recombination of electron and hole pairs and the low utilization of sunlight restrict the development of photocatalytic technology. By comparing the morphologies and hydrogen production properties of different proportions of solid solutions (CdxZn1-xS), one-dimensional (1D) Cd0.9Zn0.1S nanorods (NRs) with the best photocatalytic properties are obtained. In addition, 1D W18O49 nanowires are assembled on the surface of 1D Cd0.9Zn0.1S NRs to construct a novel 1D/1D step-scheme (S-scheme) W18O49/Cd0.9Zn0.1S heterojunction photocatalyst. The W18O49/Cd0.9Zn0.1S heterojunction expands the optical absorption capacity of Cd0.9Zn0.1S NRs to provide more energy for the photoexcitation of electrons. The optimal hydrogen production rate of W18O49/Cd0.9Zn0.1S NRs with W18O49 content of 9 wt% is as high as 66.3 mmol·h-1·g-1, which is 5.7 times and 1.6 times higher than that of Cd0.9Zn0.1S NRs and 1 wt% Pt/Cd0.9Zn0.1S NRs. The apparent quantum efficiency (AQE) of 9 wt% W18O49/Cd0.9Zn0.1S reaches 56.0 % and 25.9 % under light wavelength irradiation at 370 and 456 nm, respectively. After the 20 h cycle stability test, the activity of photocatalytic hydrogen evolution does not decrease, due that the severe photo-corrosion of Cd0.9Zn0.1S NRs is efficiently inhibited. This work not only provides a simple and controllable synthesis method for the preparation of heterojunction structure, but also opens up a new way to improve the hydrogen evolution activity and stability of sulfur compounds.