Band gap optimization of tin tungstate thin films for solar water oxidation. (18th March 2020)

• Record Type: Journal Article
• Authors: Bozheyev, Farabi; Akinoglu, Eser Metin; Wu, Lihua; Lu, Han; Nemkayeva, Renata; Xue, Yafei; Jin, Mingliang; Giersig, Michael
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 15(2020)
• Page Start: 8676
• Page End: 8685
• Publication Date: 2020-03-18
• Subjects: Thin film -- Tin tungstate -- Reactive magnetron sputtering -- Photocurrent density -- Thickness -- Band gap; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2020.01.126
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Semiconducting ternary metal oxide thin films exhibit a promising application for solar energy conversion. However, the efficiency of the conversion is still limited by a band gap of a semiconductor, which determines an obtainable internal photovoltage for solar water splitting. In this report the tunability of the tin tungstate band gap by O2 partial pressure control in the magnetron co-sputtering process is shown. A deficiency in the Sn concentration increases the optical band gap of tin tungstate thin films. The optimum band gap of 1.7 eV for tin tungstate films is achieved for a Sn to W ratio at unity, which establishes the highest photoelectrochemical activity. In particular, a maximum photocurrent density of 0.375 mA cm −2 at 1.23 VRHE and the lowest reported onset potential of −0.24 VRHE for SnWO4 thin films without any co-catalyst are achieved. Finally, we demonstrate that a Ni protection layer on the SnWO4 thin film enhances the photoelectrochemical stability, which is of paramount importance for application. Graphical abstract: Image 1 Highlights: Variation of oxygen partial pressure changes Sn to W ratio which tunes the band gap. Optimum band gap (1.7 eV) results in the highest photocurrent density (0.375 mA cm −2 ). The lowest onset potential of - 0.24 VRHE is achieved for tin tungstate film. Photoelectrochemical stability of the films is improved by NiOx protection layer. Initial open circuit potential of 0.107 V is measured upon AM 1.5 illumination.