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Anodizing of Self-Passivating WxTi1–x Precursors for WxTi1–xOn Oxide Alloys with Tailored Stability


Siol, Sebastian; Beall, Casey; Ott, Noémie; Döbeli, Max; González-Castaño, Miriam; Wick-Joliat, René; Tilley, S David; Jeurgens, Lars PH; Schmutz, Patrik; Cancellieri, Claudia (2019). Anodizing of Self-Passivating WxTi1–x Precursors for WxTi1–xOn Oxide Alloys with Tailored Stability. ACS applied materials & interfaces, 11(9):9510-9518.

Abstract

TiO2 and WO3 are two of the most important, industrially relevant earth-abundant oxides. Although both materials show complementary functionality and are promising candidates for similar types of applications such as catalysis, sensor technology, and energy conversion, their chemical stability in reactive environments differs remarkably. In this study, anodic barrier oxides are grown on solid-solution WxTi1–x alloy precursors covering a wide compositional range (0 ≤ x ≤ 1) with the goal of creating functional oxides with tailored stability. A strong Ti-cation enrichment in the surface region of the grown WxTi1–xOn layer is observed, which can be controlled by both the anodizing conditions and precursor composition. For Ti concentrations above 50 at. %, a continuous nanometer-thick TiO2 protective coating is achieved on top of a homogeneous WxTi1–xOn film as evidenced by X-ray photoelectron spectroscopy and transmission electron microscopy analyses. A comprehensive electrochemical assessment demonstrates a very stable passivation of the surface in both acidic and alkaline environments. This increase in chemical stability correlates directly with the presence of this protective TiO2 film. The results of this work provide insights into the oxidation behavior of W1–xTix alloys, but more importantly demonstrate how controlled oxidation of self-passivating alloys can lead to oxide alloys with thin, protective surface layers that otherwise would require more sophisticated deposition methods.

Abstract

TiO2 and WO3 are two of the most important, industrially relevant earth-abundant oxides. Although both materials show complementary functionality and are promising candidates for similar types of applications such as catalysis, sensor technology, and energy conversion, their chemical stability in reactive environments differs remarkably. In this study, anodic barrier oxides are grown on solid-solution WxTi1–x alloy precursors covering a wide compositional range (0 ≤ x ≤ 1) with the goal of creating functional oxides with tailored stability. A strong Ti-cation enrichment in the surface region of the grown WxTi1–xOn layer is observed, which can be controlled by both the anodizing conditions and precursor composition. For Ti concentrations above 50 at. %, a continuous nanometer-thick TiO2 protective coating is achieved on top of a homogeneous WxTi1–xOn film as evidenced by X-ray photoelectron spectroscopy and transmission electron microscopy analyses. A comprehensive electrochemical assessment demonstrates a very stable passivation of the surface in both acidic and alkaline environments. This increase in chemical stability correlates directly with the presence of this protective TiO2 film. The results of this work provide insights into the oxidation behavior of W1–xTix alloys, but more importantly demonstrate how controlled oxidation of self-passivating alloys can lead to oxide alloys with thin, protective surface layers that otherwise would require more sophisticated deposition methods.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
08 Research Priority Programs > Solar Light to Chemical Energy Conversion
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:General Materials Science
Language:English
Date:6 March 2019
Deposited On:14 Feb 2020 09:29
Last Modified:16 Feb 2020 07:07
Publisher:American Chemical Society (ACS)
ISSN:1944-8244
OA Status:Green
Publisher DOI:https://doi.org/10.1021/acsami.8b19170
Project Information:
  • : FunderSNSF
  • : Grant IDPYAPP2_160586
  • : Project TitleSolar Water Splitting: Photovoltage, Surface Dipole, and Catalysis Strategies
  • : FunderCOST Action MP1407
  • : Grant IDIZCNZ0-174856 C16.0075
  • : Project Title

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