MoS 2 /WS 2 Heterojunction for Photoelectrochemical Water Oxidation

The solar-assisted oxidation of water is an essential half reaction for achieving a complete cycle of water splitting. The search of efficient photoanodes that can absorb light in the visible range is of paramount importance to enable cost-effective solar energy-conversion systems. Here, we demonstrate that atomically thin layers of MoS 2 and WS 2 can oxidize water to O 2 under incident light. Thin films of solution-processed MoS 2 and WS 2 nanosheets display n -type positive photocurrent densities of 0.45 mA cm –2 and O 2 evolution under simulated solar irradiation. WS 2 is significantly more efficient than MoS 2; however, bulk heterojunctions (B-HJs) of MoS 2 and WS 2 nanosheets results in a 10-fold increase in incident-photon-to-current-efficiency, compared to the individual constituents. This proves that charge carrier lifetime is tailorable in atomically thin crystals by creating heterojunctions of different compositions and architectures. Our results suggest that the MoS 2 and WS 2 nanosheets and their B-HJ blend are interesting photocatalytic systems for water oxidation, which can be coupled with different reduction processes for solar-fuel production.