β-In2S3 as Water Splitting Photoanodes: Promise and Challenges

Abstract

As the interest in sustainable energy production increases, water splitting through semiconductor materials to convert solar energy directly to hydrogen energy has been extensively reported to date. Recently, the III–VI group chalcogenide semiconductors have received great attention for narrow-gap photoelectrochemical (PEC) water splitting electrodes. Among the metal sulfides, beta indium sulfide (β-In2S3) shows remarkable properties for photoelectrodes such as high photoelectric sensitivity, high photoconductivity, large photoelectric conversion yield, low toxicity, high absorption coefficient, efficient charge separation, moderate charge transport, appropriate band position, and narrow band gap. Most of its unique properties come from the defective spinel crystal structure. Despite the superior advantages, there is a serious problem of photocorrosion induced by accumulated holes on the surface of the electrodes during the photocatalytic reaction under illumination which reduces the PEC properties. Herein, we review overall physicochemical and optoelectronic properties of β-In2S3, regardless of pros and cons, followed by the discussion of assorted strategies to further improve the PEC activities.