Boosting anode kinetics in vanadium flow batteries with catalytic bismuth nanoparticle decorated carbon felt via electro-deoxidization processing

Abstract

Vanadium flow batteries (VFBs) have proven to be an ideal candidate for long-duration grid-scale energy storage. However, high power operation of VFB is still impeded by intrinsically sluggish kinetics of...

Electrochemical Deposition of Bismuth on Graphite Felt Electrodes: Influence on Negative Half-Cell Reactions in Vanadium Redox Flow Batteries

“…The HER onset potentials of the Bi/TGFs shifted to a more positive position probably due to some additional reactions. Although bismuth has been known to inhibit HER ineffectively [30,43], the onset potentials of Bi/TGF-1.6V and Bi/TGF-1.2V are indeed much closer to the TGF. The electrodeposited Bi on the graphite felt is oxidized to form BiH x by combining with H + ions in the electrolyte.…”

“…The ability for the absorption of H + ion is in the order of TGF < Bi/TGF-1.2V < Bi/TGF-1.6V < Bi/TGF-0.8V by decreasing current density [49]. The nonlinear relationship between the reaction activities of each sample to reactions (4,5) and the deposition voltage should be attributed to the morphology of Bi particles [43], which was further analyzed by the SEM results. As an intermediate product, BiHx acts as an effective catalyst for the V 3+ /V 2+ reaction, which makes the charge transfer of the reduction reaction faster in the reaction (6).…”

“…In particular, bismuth is considered 'the most cost-effective' surface catalyst in VRFBs [37][38][39][40]. The methods employed for surface modification of GF by bismuth include in situ deposition and external deposition (e.g., hydrogen reduction, hydrothermal reaction) for VRFB applications [41][42][43][44]. However, in situ deposition is affected by many conditions, such as electrolyte flow rate, electrodeposition current density and initial concentration [41,45].…”

“…By contrast, external deposition is a better controllable method to modify GF with Bi. Recently, Zhang et al introduced Bi on carbon felts by the electrodeoxidization processing in KOH and found that the VE of VRFB single-cells reached 73.4% at 400 mA/cm 2 [43]. Although bismuth has been successfully used in the electrode modification of VRFBs as a catalyst, the existing methods are not easy to apply due to extra hetero-ion introduction.…”

Recent advances and perspectives of practical modifications of vanadium redox flow battery electrodes

“…140 Zhang et al also, by a step electric deoxidization process, successfully prepared catalytic bismuth nanoparticle decorated carbon felt. 141 Bismuth nanoparticles were successfully dispersed on carbon fibres by optimising the electrode oxidation process of bismuth oxide in alkaline solution in terms of the loading content and applied voltage. This process significantly improved the anodic redox kinetics, resulting in the operation of a high-performance VRFB.…”