Designing WO 3 /CdIn 2 S 4 type-II heterojunction with both efficient light absorption and charge separation for enhanced photoelectrochemical water splitting

Abstract WO 3 is a typical photoanode material for photoelectrochemical (PEC) water splitting. However, the PEC activity of WO 3 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 CdIn 2 S 4 nanoplates with hydrothermally grown WO 3 nanowall arrays to form into a three-dimensional (3D) WO 3 /CdIn 2 S 4 heterojunction through a chemical bath deposition process. The synthesis parameters of CdIn 2 S 4 , including reaction time and temperature, have been tuned to optimize the PEC performance. The WO 3 /CdIn 2 S 4 composite photoanode prepared at 50 °C for 5 h exhibits the highest photocurrent of 1.06 mA cm −2 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 3 photoanode. The band alignment between WO 3 and CdIn 2 S 4 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 CdIn 2 S 4 and efficient charge separation originating from the type-II alignment between WO 3 and CdIn 2 S 4 .