Electrochemical impedance spectroscopic studies on niobium anodic dissolution in HF

Electrochemical impedance spectroscopic studies on niobium anodic dissolution in HF

The dissolution of niobium electrode in anodic regime in hydrofluoric acid was studied using electrochemical techniques. In the active region, complex plane plots of the impedance spectra exhibited mainly two capacitive loops. In the passive region, the spectra exhibited a mid-frequency pseudo-induc...

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Bibliographic Details
Published in:Journal of solid state electrochemistry Vol. 21; no. 11; pp. 3155 - 3167
Main Authors: Mandula, Tirumala Rao, Srinivasan, Ramanathan
Format: Journal Article
Language:English
Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2017
Springer Nature B.V
Subjects:
Analytical Chemistry
Anodic dissolution
Characterization and Evaluation of Materials
Chemistry
Chemistry and Materials Science
Computer simulation
Condensed Matter Physics
Dissolution
Electrochemical impedance spectroscopy
Electrochemistry
Energy Storage
Hafnium
Hydrofluoric acid
Niobium
Original Paper
Oxidation
Physical Chemistry
Valence
Mechanistic analysis
Niobium
Anodic dissolution
Hydrofluoric acid
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Summary:The dissolution of niobium electrode in anodic regime in hydrofluoric acid was studied using electrochemical techniques. In the active region, complex plane plots of the impedance spectra exhibited mainly two capacitive loops. In the passive region, the spectra exhibited a mid-frequency pseudo-inductive loop and a low-frequency negative resistance. X-ray photoelectron spectroscopic analysis showed that the surface contains Nb 2+ and Nb 5+ . The impedance data were analysed using equivalent circuit with Maxwell elements as well as mechanistic modelling. A four-step mechanism with a chemical and electrochemical dissolution step is proposed to explain the results. The results show that Nb with an oxidation state of 2 is likely to be an intermediates species. The simulations predict that at low over potentials, the surface is covered mainly with bare metal, whereas at high over potentials, the surface is entirely covered by passivating Nb 5+ film.
ISSN:1432-8488
1433-0768
DOI:10.1007/s10008-017-3634-z