Designing WO3/CdIn2S4 type-II heterojunction with both efficient light absorption and charge separation for enhanced photoelectrochemical water splitting.

Abstract

WO3 is a typical photoanode material for photoelectrochemical (PEC) water splitting. However, the PEC activity of WO3 photoanode is limited by its poor visible light absorption as well as severe carrier recombination at electrode/electrolyte interface. Herein, we integrate small-band-gap CdIn2S4 nanoplates with hydrothermally-grown WO3 nanowall arrays to form into a three-dimensional (3D) WO3/CdIn2S4 heterojunction through a chemical bath deposition (CBD) process. The synthesis parameters of CdIn2S4, including reaction time and temperature, have been tuned to optimize the PEC performance. The WO3/CdIn2S4 composite photoanode prepared at 50 °C for 5 h exhibits the highest photocurrent of 1.06 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) without the presence of holes scavenger, which is about 5.9 times higher than that of bare WO3 photoanode. The band alignment between WO3 and CdIn2S4 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 CdIn2S4 and efficient charge separation originating from the type II alignment between WO3 and CdIn2S4.