Surface modifications of chalcopyrite CuInS2 thin films for photochatodes in photoelectrochemical water splitting under sunlight irradiation

Abstract

Copper chalcopyrite semiconductors include a wide range of compounds that are of interest for photoelectrochemical water splitting which enables them to be used as photochatodes for H 2 generation. Among them, CuInS 2 is one of the most important materials due to its optimum band gap energy for sunlight absorption. In the present study, we investigated the application of CuInS 2 fabricated by electrodeposition as photochatodes for water splitting. Thin film of CuInS 2 chalcopyrite was formed on Mo-coated glass substrate by stacked electrodeposition of copper and indium followed by sulfurization under H 2 S flow. The films worked as a H 2 liberation electrode under cathodic polarization from a solution containing Na 2 SO 4 after loading Pt deposits on the film. Introduction of an n-type CdS layer by chemical bath deposition on the CuInS 2 surface before the Pt loading resulted appreciable improvements of H 2 liberation efficiency and a higher photocurrent onset potential. Moreover, the use of In 2 S 3 layer as an alternative n -type layer to the CdS significantly improved the H 2 liberation performance: the CuInS 2 film modified with In 2 S 3 and Pt deposits worked as an efficient photocathode for photoelectrochemical water splitting.

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