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.
In this paper, a rayon based graphite felt (R‐GF) and a polyacrylonitrile based graphite felt (PAN‐GF) are studied to clarify the influence of the precursor on the polarization effect from three aspects: concentration polarization, ohmic polarization, and electrochemical polarization. The essential difference in chemical structure between R‐GF and PAN‐GF is that the precursor material makes PAN‐GF easier to be graphitized. The higher degree of graphitization leads to a higher conductivity of PAN‐GF. At the same thickness and porosity, the conductivity of PAN‐GF is higher and the loss of ohmic polarization is smaller. These factors make PAN‐GF have better electrocatalytic properties and kinetic reversibility in the Fe/Cr electrolyte environment. While the surface roughness of R‐GF is larger, which is contributing to the diffusion and surface mass transfer of the electrolyte on the surface. The effect of precursor on the concentration polarization of R‐GF and PAN‐GF is related to the surface mass transfer, which ultimately affects the performance of ICRFB.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.