Designing WO/CdInS type-II heterojunction with both efficient light absorption and charge separation for enhanced photoelectrochemical water splitting.

WO is a typical photoanode material for photoelectrochemical (PEC) water splitting. However, the PEC activity of WO photoanode is limited by its poor visible light absorption as well as severe carrier recombination at the electrode/electrolyte interface. Herein, we integrate small-band-gap CdInS nanoplates with hydrothermally grown WO nanowall arrays to form into a three-dimensional (3D) WO/CdInS heterojunction through a chemical bath deposition process. The synthesis parameters of CdInS, including reaction time and temperature, have been tuned to optimize the PEC performance. The WO/CdInS composite photoanode prepared at 50 °C for 5 h exhibits the highest photocurrent of 1.06 mA cm at 1.23 V versus reversible hydrogen electrode without the presence of holes scavenger, which is about 5.9 times higher than that of bare WO photoanode. The band alignment between WO and CdInS is confirmed by the ultraviolet-visible light absorption spectra and ultraviolet photoelectron spectra. The PEC performance enhancement is attributed to the enhanced light absorption benefiting from the small band gap of CdInS and efficient charge separation originating from the type-II alignment between WO and CdInS.