A new strategy for integrating abundant oxygen functional groups into carbon felt electrode for vanadium redox flow batteries

Abstract

The effects of surface treatment combining corona discharge and hydrogen peroxide (H2O2) on the electrochemical performance of carbon felt electrodes for vanadium redox flow batteries (VRFBs) have been thoroughly investigated. A high concentration of oxygen functional groups has been successfully introduced onto the surface of the carbon felt electrodes by a specially designed surface treatment, which is mainly responsible for improving the energy efficiency of VRFBs. In addition, the wettability of the carbon felt electrodes also can be significantly improved. The energy efficiency of the VRFB cell employing the surface modified carbon felt electrodes is improved by 7% at high current density (148 mA cm−2). Such improvement is attributed to the faster charge transfer and better wettability allowed by surface-active oxygen functional groups. Moreover, this method is much more competitive than other surface treatments in terms of processing time, production costs, and electrochemical performance.

Graphene‐Nanowall‐Decorated Carbon Felt with Excellent Electrochemical Activity Toward VO2+/VO2+ Couple for All Vanadium Redox Flow Battery

“…Charge–discharge voltage profiles of the VRFBs with CF‐G‐1 and CF are shown in Figure 5b. For CF‐G‐1 sample, the onset potential of charging branch is lower than that of CF, opposite behavior is observed for the discharging branch, implying the redox reactions on the CF‐G‐1 endures much smaller electrochemical polarization during the battery operation 44, 45, 46. As a result, more capacity can be obtained over the same operation potential window (0.7–1.7 V), about 20.5 Ah L −1 discharge capacity for CF‐G‐1 and 14.3 Ah L −1 discharge capacity for CF.…”

Vanadium microfluidic fuel cell with novel multi-layer flow-through porous electrodes: Model, simulations and experiments

“…Herein, we assume that modified CP exhibits superior k O and A compared with the non-modified CP (by a factor of 10 in line with previous studies) [55,59]. For the base case, CP was solely implemented on all layers.…”

“…The significance of the above parameters is highlighted in the studies of Kim where differences by one order of magnitude in k O (towards the VO 2þ =VO þ 2 redox reaction) and A were reported on modified carbon paper electrodes (i.e. mild oxidation, plasma treatment, corona discharge and gamma-ray irradiation) [55,59].…”

“…Yet, without any modification, carbon fibers exhibit poor electrochemical activity. A great deal of work has been conducted in the modification of carbon fiber electrodes so as to boost their electrochemical properties [46][47][48][49][50][51][52][53][54][55][56][57][58][59]. Several metal and metal compounds such as Pt, Pd, Bi, Au, IrO 2 and RuO 2 have been successfully deposited/impregnated on the graphite fibers leading to superior catalytic activity [60].…”

“…Other modification routes have been reported involving chemical and thermal routes (viz. surface oxidation and surface functionalization) leading to an increased and more activated carbon surface area [49,59]. Regarding the operation of the MFC, a balance between performance and cost is imperative when taking into account the novel catalyst materials and the energy consumed by the modification processes.…”