fig5

Figure 5. (A) Discharge capacity and CE curves of Fe-S RFB cells in the presence and absence of 30.0 mM FMN-Na; (B) Comparison of EE values and capacity-voltage profiles of the corresponding Fe-S RFBs. For (A) and (B), the cell composition was 40.0 mL 2.0 M K₂S + 1.0 M KCl, with or without FMN-Na | PFSA | 20.0 mL 0.25 M K₄[Fe(CN)₆] + 0.25 M Na₄[Fe(CN)₆] + 1.0 M KCl; (C) Cell performance of the Fe-S RFB following the midway addition of 30.0 mM FMN-Na at a current density of 40 mA cm^-2; (D) Corresponding voltage-capacity profiles recorded before and after FMN-Na addition. FMN-Na: Flavin mononucleotide sodium salt; CE: Coulombic efficiency; EE: energy efficiency; VE:voltage efficiency; CR: capacity retention; Fe-S RFB: ferrocyanide-polysulfide redox flow battery; PFSA: perfluorosulfonic acid membrane.