PVP Treatment Induced Gradient Oxygen Doping in In2S3 Nanosheet to Boost Solar Water Oxidation of WO3 Nanoarray Photoanode

Abstract The photoelectrochemical performance of the WO 3 photoanode is limited by the severe charge recombination in the bulk phase and at the WO 3 /electrolyte interface. Herein, In 2 S 3 nanosheets are integrated onto the surface of the WO 3 nanowall array photoanode, followed by a facile polyvinylpyrrolidone (PVP) solution treatment. The PVP treatment results in sulfur vacancies and a gradient oxygen doping into In 2 S 3 from surface to interior, which induces the formation of a gradient energy band distribution. The gradient band structured In 2 S 3 and type II band alignment at the WO 3 /In 2 S 3 interface simultaneously create a channel that favors photogenerated electrons to migrate from the surface to the conductive substrate, thereby suppressing bulk carrier recombination. Meanwhile, the sulfur vacancies and oxygen doping contribute to increased charge carrier concentration, prolonged carrier lifetime, more active sites, and small interfacial transfer impedance. As a consequence, the PVP treated WO 3 /In 2 S 3 heterostructure photoanode exhibits a significantly enhanced photocurrent of 1.61 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) and negative onset potential of 0.02 V versus RHE.