Determination of Fe oxidation states in the B-site ordered perovskite-type Ba2Ca0.67Fe0.33NbO6−δ at the surface (nano-scale) and bulk by variable temperature XPS and TGA and their impact on electrochemical catalysis

Wang Hay Kan; Min Chen; Jong-Seong Bae; Bok-Hee Kim; Venkataraman Thangadurai

doi:10.1039/C4TA00811A

Determination of Fe oxidation states in the B-site ordered perovskite-type Ba₂Ca_0.67Fe_0.33NbO_6−δ at the surface (nano-scale) and bulk by variable temperature XPS and TGA and their impact on electrochemical catalysis†

Wang Hay Kan,^a Min Chen,^a Jong-Seong Bae,^b Bok-Hee Kim^c and Venkataraman Thangadurai*^a

* Corresponding authors

^a Department of Chemistry, University of Calgary, 2500 University Dr. NW, Calgary, AB, Canada T2N 1N4
E-mail: vthangad@ucalgary.ca
Tel: +1 403 210 8649

^b Division of High Technology Materials Research, Korea Basic Science Institute Busan Center, 1275 Jisa-dong, Gangseo-gu, Busan 618-230, South Korea

^c Department of Hydrogen and Fuels Engineering, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, South Korea

Abstract

In this study, we analyzed the surface and bulk valences of Fe in the double perovskite-type Ba₂Ca_0.67Fe_0.33NbO_6−δ by both variable temperature X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The concentration of Fe²⁺ near-surface was found to be about 3 times higher than that in the bulk sample. The electrochemical performance of Ba₂Ca_0.67M_0.33NbO_6−δ (M = Mn, Fe and Co) was assessed by ac impedance spectroscopy using a Zr_0.84Y_0.16O_1.92 (YSZ) supported half-cell. The area specific polarization resistances (ASR) of all samples were found to decrease with increasing temperature. We speculate that ASR for H₂ oxidation are correlated with the higher concentrations of low valence Fe²⁺ species near-surface (nano-scale), as demonstrated for Ba₂Ca_0.67Fe_0.33NbO_6−δ.

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DOI: https://doi.org/10.1039/C4TA00811A
Article type: Paper
Submitted: 16 Feb 2014
Accepted: 25 Mar 2014
First published: 02 May 2014

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J. Mater. Chem. A, 2014,2, 8736-8741

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Determination of Fe oxidation states in the B-site ordered perovskite-type Ba₂Ca_0.67Fe_0.33NbO_6−δ at the surface (nano-scale) and bulk by variable temperature XPS and TGA and their impact on electrochemical catalysis

W. H. Kan, M. Chen, J. Bae, B. Kim and V. Thangadurai, J. Mater. Chem. A, 2014, 2, 8736 DOI: 10.1039/C4TA00811A

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Journal of Materials Chemistry A

Determination of Fe oxidation states in the B-site ordered perovskite-type Ba₂Ca_0.67Fe_0.33NbO_6−δ at the surface (nano-scale) and bulk by variable temperature XPS and TGA and their impact on electrochemical catalysis†

Abstract

Supplementary files

Article information

Download Citation

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Determination of Fe oxidation states in the B-site ordered perovskite-type Ba₂Ca_0.67Fe_0.33NbO_6−δ at the surface (nano-scale) and bulk by variable temperature XPS and TGA and their impact on electrochemical catalysis

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Journal of Materials Chemistry A