Vanadium—Polydopamine Flow Battery

Abstract

Dopamine (DA) exhibits quinone/hydroquinone redox activity at ~0.77 V vs. SHE. As the potential is sufficiently high, this can be a replacement to the VO2+/VO2+ redox couple (catholyte) of the vanadium redox flow battery. But DA undergoes polymerization into polydopamine (PDA) while cycling in the flow battery. Therefore, a hybrid flow battery was constructed with PDA coated thermally activated graphite felt positive electrode and V3+/V2+ in 3 M H2SO4 anolyte. The vanadium-PDA flow battery exhibits a capacity of ~275 mAh gPDA-1 in the first cycle. When the battery was subjected to continuous galvanostatic charge-discharge up to 300 cycles, a capacity retention of ~86 % was observed with coulombic efficiency close to > 99 %. Besides, energy efficiency of ~63 % at a current density of 5 A g-1 was observed. The peak power density of the battery was found to be ~8.83 W g-1 at a current density of ~14.31 A g-1.

Hydrobromide Salt of Tribromodopamine as a Positive Electroactive Species with a Three-Electron Redox Process for Redox Flow Battery Applications

“…Although crossover-free scenarios should lead to effective capacity retention, GCD cycling confirmed capacity loss. In our previous report, dopamine was used as the catholyte, which undergoes electrochemical polymerization at the unsubstituted sites of the aromatic ring, and hence a rapid capacity degradation (∼79%) was observed within 10 GCD cycles, and the observed capacity was only due to polydopamine. However, in this study, we substituted these sites with a −Br group, and hence, we did not observe such severe capacity degradation within a few initial GCD cycles.…”

“…DA is known to undergo polymerization during cycling, as reported in the literature. − Hence, the unsubstituted aromatic sites of DA were substituted with -Br to obtain DABr 3 ·HBr (Scheme ). The 1 H and 13 C NMR spectra are given in Figures S1 and S2.…”

“…All of the molecules were optimized and calculated at the B3LYP/6-311+G­(d,p) level, while the “conductor-like polarizable continuum model” (CPCM) was adopted to determine the solvent (i.e., water) effect. The Δ G of the reactions was calculated according to Scheme …”

“…9,10 Polydopamine, an electron-rich aromatic redox material, has a lower redox potential than DA. 11 The electropolymerization is initiated through the unsubstituted sites on the benzene ring of DA; therefore, to inhibit the polymerization, the natural remedy would be functionalizing these sites with suitable substituents. The nature of the substituent greatly influences the electron density at the DA core and hence its redox HBr-V static batteries, where 1,5-AQDS = anthraquinone-1,5-disulfonic acid disodium salt and V = vanadium in its 3+/2+ oxidation states) to establish its suitability for energy storage applications.…”

“…Dopamine (DA), a naturally occurring redox molecule, is a suitable catholyte for RFB because of its high redox potential of 0.8 V vs SHE. However, DA undergoes electrochemical polymerization even under highly acidic conditions. , Polydopamine, an electron-rich aromatic redox material, has a lower redox potential than DA . The electropolymerization is initiated through the unsubstituted sites on the benzene ring of DA; therefore, to inhibit the polymerization, the natural remedy would be functionalizing these sites with suitable substituents.…”