Development of Hybrid Tungsten Oxide Photoanodes Admixed with Borododecatungstate-Polyanion Modified-Hematite: Enhancement of Water Oxidation upon Irradiation with Visible Light. (10th October 2015)

• Record Type: Journal Article
• Authors: Miecznikowski, Krzysztof; Ramírez, Alejandra; Fiechter, Sebastian; Bogdanoff, Peter; Szaniawska, Ewelina; Wadas, Anna; Kulesza, Pawel J.
• Is Part Of: Electrochimica acta. Volume 179(2015)
• Page Start: 379
• Page End: 385
• Publication Date: 2015-10-10
• Subjects: mesoporous tungsten oxide -- Keggin-type borotungstic acid -- hematite -- water splitting -- oxygen evolution; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.05.001
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Sol-gel aggregation approach has been used to prepare hybrid tungsten oxide based films admixed with Keggin-type borotungstic acid and the polyanion modified-hematite (Fe2 O3 ). Relative to conventional mesoporous-WO3, the WO3 -based hybrid films (photoanodes) have yielded significantly larger water oxidation photocurrents (both in 0.5 M H2 SO4 and in 0.5 M NaCl at pH = 2) upon illumination with visible light. Oxygen has been detected in vicinity of WO3 -based hybrid photoanode with use of Pt microdisk electrode. Hybrid (admixed doped) WO3 -based films are promising photoanodes for the visible-light driven water splitting. Abstract: A typical procedure based on sol-gel aggregation for the fabrication of mesoporous WO3 photoanodes was modified and used produce modified tungsten oxide films by utilizing the tungstic acid sol admixed with Keggin-type borotungstic acid (H5 BW12 O40 ) or the borotungstic acid–stabilized hematite (Fe2 O3 ). Physicochemical properties (structure, morphology and spectroscopic identity) of the resulting hybrid (composite) WO3 films were assessed using X-ray diffraction, scanning electron microscopy, as well as UV-Vis and Raman spectroscopies. During photoelectrochemical experiments with a solar cell system operating in 0.5 mol dm −3 H2 SO4 in three-electrode configuration, the composite WO3 films acting as photoanodes yielded (following illumination with visible light) significantly (up to 80%) larger water oxidation photocurrents (at potentials higher than 0.75 V vs. RHE), relative to the performance of analogous bare (pristine) mesoporous tungsten oxide films. Independent voltammetric diagnostic experiments with Pt microdisk electrode implied the appearance of oxygen during photooxidation of water. The enhancement effect was the most pronounced for WO3 films admixed with borotungstic acid–stabilized hematite. The observed phenomena could be rationalized either in terms of the presence of new conduction band structures in composite WO3 films or a marked increase in the degree of hydration of the composite oxide structures regardless of the annealing at high temperatures (450 °C). It was also apparent from our experiments in 0.5 mol dm −3 NaCl, the systems were also applicable to sea-water-type environments.