Thin films of pure vanadium nitride: Evidence for anomalous non-faradaic capacitance

Thin films of pure vanadium nitride: Evidence for anomalous non-faradaic capacitance An impressive gravimetric capacitance of 1300 F g−1 (surface capacitance ∼3.3 mF cm−2) reported by Choi et al., 2006 for nanosized vanadium nitride has stimulated considerable interest in vanadium nitride as a potential electrode material for energy storing systems – supercapacitors. The postulated mechanism of charge storage in vanadium nitride materials involves redox reactions in the thin surface layer of vanadium oxide while the core vanadium nitride serves exclusively as a conducting platform. In this study we have synthesized pure oxygen-free vanadium nitride films and have found that they are capable of delivering a surface capacitance of up to ∼3 mF cm−2 at a potential scan rate of 3 mV s−1 and ∼2 mF cm−2 at a potential scan rate of 1 V s−1 in aqueous electrolytes. Combining electrochemical testing with X-ray photoelectron spectroscopy characterization has revealed that redox reactions play no or little role in the electrochemical response of pure VN, in contrast to the common wisdom stemming from the electrochemical response of oxygen-containing films. An alternative charge storage mechanism – space charge accumulation in a subsurface layer of ∼100 nm – was put forward to explain the experimentally observed capacitance of VN films in aqueous electrolytes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Power Sources Elsevier

Thin films of pure vanadium nitride: Evidence for anomalous non-faradaic capacitance

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Publisher
Elsevier
Copyright
Copyright © 2016 Elsevier B.V.
ISSN
0378-7753
D.O.I.
10.1016/j.jpowsour.2016.05.093
Publisher site
See Article on Publisher Site

Abstract

An impressive gravimetric capacitance of 1300 F g−1 (surface capacitance ∼3.3 mF cm−2) reported by Choi et al., 2006 for nanosized vanadium nitride has stimulated considerable interest in vanadium nitride as a potential electrode material for energy storing systems – supercapacitors. The postulated mechanism of charge storage in vanadium nitride materials involves redox reactions in the thin surface layer of vanadium oxide while the core vanadium nitride serves exclusively as a conducting platform. In this study we have synthesized pure oxygen-free vanadium nitride films and have found that they are capable of delivering a surface capacitance of up to ∼3 mF cm−2 at a potential scan rate of 3 mV s−1 and ∼2 mF cm−2 at a potential scan rate of 1 V s−1 in aqueous electrolytes. Combining electrochemical testing with X-ray photoelectron spectroscopy characterization has revealed that redox reactions play no or little role in the electrochemical response of pure VN, in contrast to the common wisdom stemming from the electrochemical response of oxygen-containing films. An alternative charge storage mechanism – space charge accumulation in a subsurface layer of ∼100 nm – was put forward to explain the experimentally observed capacitance of VN films in aqueous electrolytes.

Journal

Journal of Power SourcesElsevier

Published: Aug 30, 2016

References

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