Efficient AcFc-[Fe III (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 (k 0 ) of AcFc was found to be greater than that of [Fe(acac) 3 ]. However, the value of k 0 was not affected by the variable temperature. 1 H 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.