Photoelectrochemical Water Splitting by In2S3/In2O3 Composite Nanopyramids

Abstract

Photoelectrochemical (PEC) water-splitting reaction becomes an important path for the requirement of the fulfillment of global energy demand. For PEC water-splitting reactions, here In2O3 is grown in situ in the nanopyramidal structure of In2S3 via a simple hydrothermal technique. The limited supply of S2– in the reaction medium plays an important role in the development of In2O3 along with In2S3, leading to the In2S3/In2O3 nanocomposite. The In2S3/In2O3 nanocomposite shows an enriched carrier density compared to bare In2S3. The optimum amount of In2O3 in the composite helps to achieve efficient photoactivity. In addition, the observed negative shift of the flat band potential of the nanocomposite demonstrates the assistance of the early onset potential. Moreover, the In2S3/In2O3 nanocomposite shows improved visible light absorbance due to its pyramidal nanostructure. It can generate a high photoconversion efficiency of ∼0.55% at 0.77 V versus the reversible hydrogen electrode (RHE) in 0.5 M Na2SO4. The stability of the In2S3/In2O3 nanopyramid is determined under chopped illumination condition for 1000 s, which shows decay in the stability in the Na2SO4 medium. Importantly, to widen the applicability of the In2S3/In2O3 composite, the PEC water-splitting performance is determined in 3.5% saline water. Under such a corrosive environment, In2S3/In2O3 can show efficient photoactivity as well as outstanding stability. It can generate a photocurrent density of 0.83 mA/cm2 under an applied potential of 1.18 V versus the RHE. The present research suggests the development of the In2S3/In2O3 nanopyramid composite as a chloride environment-withstanding and high corrosion-resistant photoanode. The advantage of the faceted nanopyramidal structure and the composite is focused here. It paves an avenue for the development and engineering of highly persistent seawater-splitting photoelectrodes, which provides an opportunity to use the vast seawater on the Earth as an energy carrier.