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Issue 11, 2016
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Photo-assisted electrodeposition of manganese oxide on TaON anodes: effect on water photooxidation capacity under visible light irradiation

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Abstract

The synergistic effect of coupling a photooxidation catalyst, tantalum oxynitride, and manganese oxide (MnOx) as electrooxidation catalyst in multi-component photoanodes for water oxidation is explored in near-neutral solutions under visible light irradiation (λ > 400 nm). The anodes have been formed by using different electrochemical methods to deposit MnOx on screen-printed TaON films, pre-modified with TiO2 coatings (TiO2–TaON). By using SEM/EDX, ICP-MS analysis of the amount of Mn deposited and, electrochemical techniques, we demonstrate that selective deposition of fine-structured nm-sized MnOx flakes on the photocatalytically active TiO2–TaON surface is achieved when the electrodeposition is carried out under visible light irradiation, but not in the dark. The MnOx/TiO2–TaON anodes produced using the photo-assisted method exhibit improved activity and better long-term stability during water photooxidation under visible light irradiation when compared to the TiO2–TaON films modified with MnOx in dark. A 7-fold enhancement in the oxidative photocurrent densities under voltammetric and chronoamperometric conditions in 0.1 M Na2SO4 (pH = 6) is observed for the films prepared by the photo-assisted method. The Mn-loading in the best performing films is ca. 0.8 wt% and higher loadings were found to lower the photocatalytic activity. Continuous water photooxidation over MnOx/TiO2–TaON anodes in 0.1 M Na2SO4 (pH = 6) at potentials more positive than ca. 1.0 V vs. reversible hydrogen electrode coarsens the fine structure of the MnOx material, and this structural degradation is mirrored in a slow deterioration of the photocatalyst performance.

Graphical abstract: Photo-assisted electrodeposition of manganese oxide on TaON anodes: effect on water photooxidation capacity under visible light irradiation

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Publication details

The article was received on 28 Aug 2015, accepted on 30 Dec 2015 and first published on 04 Jan 2016


Article type: Paper
DOI: 10.1039/C5CY01432H
Citation: Catal. Sci. Technol., 2016,6, 3745-3757
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    Photo-assisted electrodeposition of manganese oxide on TaON anodes: effect on water photooxidation capacity under visible light irradiation

    S. Singh Gujral, A. N. Simonov, X. Fang, M. Higashi, T. Gengenbach, R. Abe and L. Spiccia, Catal. Sci. Technol., 2016, 6, 3745
    DOI: 10.1039/C5CY01432H

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