The Synthesis, Characterisation and Electroanalysis of Organic Redox Active Molecules

With global efforts to shift to renewable energy sources increasing, the requirement for cheap, sustainable, and effective energy storage solutions have increased also. Current battery technologies are limited both by their reliance on finite resources and versatility, flow battery technologies such as those seen in currently deployed vanadium redox flow batteries (VRFBs) offer an alternative to traditional energy storage solutions but are still dependant on a financially volatile and finite commodity. Novel organic redox flow batteries (ORFBs) present a sustainable alternative to current flow battery systems, however are hindered by their performance, cost, and often are not derived from sustainable sources. This paper seeks to find an organic redox active molecule with the versatility to operate effectively within a range of conditions. The most promising molecule was found to be a water soluble anionic alloxazine (11d) derived from riboflavin - which presents a redox potential of -0.774 V in unbuffered acidic conditions and -0.907 V in unbuffered neutral conditions vs. an Ag/AgCl reference electrode making it suitable as an anolyte within flow battery systems. This molecule was shown to operate in a flow battery setup coupled with HBr/Br2 in acidic conditions with an Ecell value of 1.818 V and a maximum observed current efficiency of ~44 % and a capacity fade of ~20 %.