Variability within a single type of polyacrylonitrile-based graphite felt after thermal treatment. Part II: chemical properties

Rabbow, Thomas; Trampert, Markus; Pokorný, Peter; Binder, Paul; Whitehead, Adam

doi:10.1016/j.electacta.2015.05.058

Cited by 37 publications

(26 citation statements)

References 37 publications

(47 reference statements)

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“…The increase in EDLC increases with the BET for the surface‐treated materials (AGFs). The values for GF/PAN and AGF/PAN are largely in line with recently published values . Figure and depict double half‐cell measurements of the different carbon felts using positive and negative vanadium electrolytes at a constant SoC of 50 %.…”

Section: Resultssupporting

confidence: 88%

“…The most common procedure used in practice, however, is the surface oxidation treatment of the felts (mostly by baking in air at 400–700 °C), which is performed in order to produce surface functional groups which facilitate the wetting of the fibers and which are also assumed to promote faster charge‐transfer kinetics of redox species . Modifications based on wet‐chemical etching, mixed gas treatment, steam, plasma or gamma rays have also been proposed.…”

Section: Introductionmentioning

confidence: 99%

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Steady‐State Measurements of Vanadium Redox‐Flow Batteries to Study Particular Influences of Carbon Felt Properties

2017

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Carbon felts based on rayon and polyacrylonitrile (PAN) precursors constitute the most widespread porous electrode material for vanadium redox‐flow batteries. Since the raw materials exhibit rather poor wettability, it has become common practice to apply oxidative surface treatments prior to use in flow batteries. This study investigates the electrode‐specific effects of raw and thermally oxidized (PAN and rayon‐based) carbon felts on their electrochemical behavior at the negative and the positive electrode in all vanadium redox‐flow batteries. By means of steady‐state single cell measurements, it is verified that oxidative surface treatment has opposite effects on negative and positive redox couples and that the beneficial influence on the vanadium redox‐flow battery performance is mainly brought about by substantially improved charge‐transfer kinetics at the negative electrode. Similarly, the type of carbon precursor and the degree of graphitic character have a particular impact on the electrode behavior.

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Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Steady‐State Measurements of Vanadium Redox‐Flow Batteries to Study Particular Influences of Carbon Felt Properties

2017

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“…• C (under Argon atmosphere), inherently exhibit insufficient electrolyte wettability 10,11 and were therefore subjected to brief thermal surface oxidation (air, 750…”

Section: Methodsmentioning

confidence: 99%

“…[6][7][8][9][10][11] In the literature they are widely referred to as 'graphite' felts as they are processed at high temperatures similar to those used in the manufacturing of synthetic graphite. The fraction of crystalline domains, however, amounts to less than 50% 10 and the crystallographic definition of graphite 12 is hardly fulfilled.…”

mentioning

confidence: 99%

Parasitic Hydrogen Evolution at Different Carbon Fiber Electrodes in Vanadium Redox Flow Batteries

Schweiss

Pritzl

Meiser

2016

J. Electrochem. Soc.

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Carbon fiber-based fabrics such as felts, cloths or papers are porous electrode materials that are widely used in redox flow batteries. This study investigates the effect of the carbon fiber properties on hydrogen evolution at the negative electrode, which occurs as an important side reaction in redox flow batteries employing acidic electrolytes. The lowest hydrogen evolution rate was observed at carbon fibers with a high content of graphitic domains which have been subjected to surface oxidation pre-treatment. By contrast, felt materials consisting of fibers with a largely amorphous character produce elevated amounts of hydrogen during battery charging. Differences between rayon-and polyacrylonitrile (PAN)-derived carbon fibers point toward the important role of nitrogen species. © The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.1281609jes] All rights reserved. Redox flow batteries are regarded as promising candidates for large-scale electrochemical storage systems for energy generated from fluctuating sources such as wind farms or photovoltaic systems.1-5 One of their widely acclaimed features is their inherent safety. Among other aspects, this is owing to the fact that the active masses consist of rather dilute, aqueous solutions of redox species (typically 1.5 to 3 molar) which are continuously circulated through an electrochemical reactor during operation. Consequently, only a small fraction of the redox species is present at any given time in the electrochemically active area, while the major part remains in electrolyte tanks, where it acts as a powerful thermal buffer.The obvious drawback of the aqueous cell chemistry is the relatively small electrochemical window, which is limited by the onset of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Since common electrolytes contain strong acids with concentrations of up to 4 moles per liter in order to provide high ionic conductivity, the electrochemical window is reduced even further.Three-dimensional porous carbon electrodes such as felts, which are commonly manufactured from rayon (cellulose) or polyacrylonitrile (PAN) precursors, are well suited for these batteries since they come at a low cost, have a large surface area and exhibit sufficiently large overpotentials against hydrogen and oxygen evolution. [6][7][8][9][10][11] In the literature they are widely referred to as 'graphite' felts as they are processed at high temperatures similar to those used in the manufacturing of synthetic graphite. The fraction of crystalline domains, however, amounts to less than 50% 10 and the crystallographic d...

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“…That means, in the case of using GF or CF with different graphitization degree, GF and CF have different electrocatalytic activities through hot air and Bi. Therefore, it is inevitable that no consistent treatment method can be found in the literature for the above characteristics of GF and CF . The electrochemical characteristics of samples in positive reaction and negative reaction suggest that the electrode activity in the ICRFB is affected not only by the oxygen functional groups but also by the graphitization degree.…”

Section: Resultsmentioning

confidence: 99%

Investigations on physicochemical properties and electrochemical performance of graphite felt and carbon felt for iron‐chromium redox flow battery

et al. 2020

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Summary In this paper, polyacrylonitrile‐based graphite felt (GF), carbon felt (CF) and the effect of thermal activation on them with or without the catalyst (BiCl3) are comprehensively investigated for iron‐chromium redox flow battery (ICRFB) application. The physical‐chemical parameters of GF and CF after the thermal activation is affected significantly by their graphitization degree, oxygen functional groups, and surface area. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results manifest that GF and CF before and after the thermal activation have different electrocatalytic activities owing to oxygen functional groups number increase and the graphitization degree decrease. In terms of the capacity decay rate, as oxygen functional groups provide shorter electrocatalytic pathways than bismuth ions, the performance of GF and CF after the thermal activation is more ideal. As a result, GF before and after the thermal activation exhibits higher efficiency (EE: 86%) and better stability at a charge‐discharge current density of 60 mA·cm−2 than those of CF during charge‐discharge cycling, as the dominant limitation in an ICRFB is ohmic and activation polarization. Therefore, GF after thermal activation together with the addition of BiCl3 in the electrolyte is a more promising electrode material for ICRFBs application than CF.

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Variability within a single type of polyacrylonitrile-based graphite felt after thermal treatment. Part II: chemical properties

Cited by 37 publications

References 37 publications

Steady‐State Measurements of Vanadium Redox‐Flow Batteries to Study Particular Influences of Carbon Felt Properties

Steady‐State Measurements of Vanadium Redox‐Flow Batteries to Study Particular Influences of Carbon Felt Properties

Parasitic Hydrogen Evolution at Different Carbon Fiber Electrodes in Vanadium Redox Flow Batteries

Investigations on physicochemical properties and electrochemical performance of graphite felt and carbon felt for iron‐chromium redox flow battery

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