Characterization of Carbon Felt Electrodes for Vanadium Redox Flow Batteries: Impact of Treatment Methods

Abstract

In this study, we investigated the influence of thermal treatment, soaking in H 2 SO 4 and electrochemical ageing on commercially available carbon felt materials from SGL carbon. We compared both the influence of the pre-treatment (carbonization or graphitization) and the influence of the precursor (Rayon or PAN). By thermogravimetric analysis coupled with mass spectrometry (TGA-MS) we showed, that after thermal treatment, the thermal stability was lower for carbonized felts compared to graphitized felts and the Rayon based felts were more stable than PAN based ones. Soaking had a stronger impact on the thermal stability of PAN based felts, whereas it was similar to the electrochemical ageing for Rayon based felts. X-ray photoelectron spectroscopy and Raman spectroscopy revealed that thermal treatment reduces the overall surface oxygen content for all felt types and the degree of graphitization doesn't change, but the content of single bonded oxygen was increased for graphitized carbon felts, only. For carbonized felts, thermal treatment highly reduced the electrochemical activity characterized by cyclic voltammetry due to a reduced overall oxygen content and increased C=O and C=C contents. In this work, we provide a comprehensive overview of commercially available carbon felts and characterize the effects of several treatment methods.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.52.96.103 Downloaded on 2018-09-04 to IP A2578 Journal of The Electrochemical Society, 165 (11) A2577-A2586 (2018) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.52.96.103 Downloaded on 2018-09-04 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 141.52.96.103 Downloaded on 2018-09-04 to IP

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

“…Further peak fitting of the C 1s and O 1s peaks for each sample is shown in Figure , and the fitting results are shown in Table . Among them, the C 1s spectra is fitted at five peaks of 284.1, 285, 285.96, 288.2, 290.4, and 291.61 eV, corresponding to C═C bond (graphite carbon), C─C bond (defective carbon), C─O─H bond, C═O bond, O═C─OH bond, and π‐π*, respectively . The O 1s spectra have been split into three peaks at 531.8, 533, and 535 eV, respectively, which is analogous to the binding energies of C═O groups, C─OH/C─O─C groups, and ether‐like species .…”

“…Among them, the C 1s spectra is fitted at five peaks of 284.1, 285, 285.96, 288.2, 290.4, and 291.61 eV, corresponding to C═C bond (graphite carbon), C─C bond (defective carbon), C─O─H bond, C═O bond, O═C─OH bond, and π-π*, respectively. 39 The O 1s spectra have been split into three peaks at 531.8, 533, and 535 eV, respectively, which is analogous to the binding energies of C═O groups, C─OH/C─O─C groups, and ether-like species. 40 From the quantitative results of XPS, it can be seen that the thermal treatment reduces the number of graphite carbon (C═C) of T-GF and T-CF.…”

Polarization Effects of a Rayon and Polyacrylonitrile Based Graphite Felt for Iron‐Chromium Redox Flow Batteries

“…The quantified results of peaking are listed in Table S1. In Figure (a), the spectra of C 1s can be fitted at six peaks of 284.1, 285, 285.96, 288.2, 290.4, and 291.61 eV, corresponding to C=C, C−H, C−O‐R, C=O, O=C‐OH and π‐π*, respectively . Among them, C=C, C=O, O=C‐OH belong to the sp 2 hybrid structure of the C atom, while C−H and C−O−R belong to sp 3 hybrid structure of the C atom.…”

“…Similarly, the ratio of C=O/C−O in the O atom can be obtained by dividing the sum of the C=O peak areas after the O 1s peak by the sum of the C−O peak areas. The specific calculation formula is as follows: …”

“…In Figure 3(a), the spectra of C 1s can be fitted at six peaks of 284.1, 285, 285.96, 288.2, 290.4, and 291.61 eV, corresponding to C=C, CÀ H, CÀ O-R, C=O, O=C-OH and π-π*, respectively. [26] Among them, C=C, C=O, O=C-OH belong to the sp 2 hybrid structure of the C atom, while CÀ H and CÀ OÀ R belong to sp 3 hybrid structure of the C atom. The C=C bond belongs to saturated carbon, and the CÀ H, CÀ OÀ R, C=O, and O=C-OH bonds belong to unsaturated carbon.…”