Efficient AcFc-[FeIII(acac)3] Redox Couple for Non-aqueous Redox Flow Battery at Low Temperature

The temperature dependency of the electrochemical analysis of acetyl ferrocene (AcFc) and iron(III) acetylacetonate ([Fe(acac)₃]) has been investigated for non-aqueous redox flow batteries (NARFBs). AcFc and [Fe(acac)₃] were utilized as catholyte and anolyte species, respectively, in an electrochemical cell with a cell voltage of 1.41 V and Coulombic efficiencies >99% for up to 50 total cycles at room temperature (RT, 25 °C). Experiments with a rotating ring disk electrode (RRDE) indicate that the diffusion coefficient reduces with decreasing temperature from 25 °C to 0 °C, yet the overall storage capacity was higher than that of an aqueous redox flow battery (ARFBs). The electrochemical kinetic rate constant (k₀) of AcFc was found to be greater than that of [Fe(acac)₃]. However, the value of k₀ was not affected by the variable temperature. ¹H NMR investigations reveal that temperature change during battery trials did not occur in any structural modification. The obtained result demonstrates the suitability of this battery at low temperatures.