Redox flow batteries (RFBs) present an opportunity to
bridge the
gap between the intermittent availability of green energy sources
and the need for on-demand grid level energy storage. While aqueous
vanadium-based redox flow batteries have been commercialized, they
are limited by the constraints of using water as an electrochemical
solvent. Nonaqueous redox flow battery systems can be used to produce
high voltage batteries due to the larger electrochemical window in
nonaqueous solvents and the ability to tune the redox properties of
active materials through functionalization. Iron porphyrins, a class
of organometallic macrocycles, have been the subject of many studies
for their photocatalytic and electrocatalytic properties in nonaqueous
solvents. Often, iron porphyrins can undergo multiple redox events
making them interesting candidates for use as anolytes in asymmetrical
redox flow batteries or as both catholyte and anolyte in symmetrical
redox flow battery systems. Here the electrochemical properties of
Fe(III)TPP species relevant to redox flow battery electrolytes are
investigated including solubility, electrochemical properties, and
charge/discharge cycling. Commonly used support electrolyte salts
can have reactivities that are often overlooked beyond their conductivity
properties in nonaqueous solvents. Parasitic reactions with the cations
of common support electrolytes are highlighted herein, which underscore
the careful balance required to fully assess the potential of novel
RFB electrolytes.