Quantification of active material crossover in organic redox flow batteries using ultraviolet-visible spectrophotometry

The need for development of renewable energy storage has led to an increased interest in redox flow batteries. However, much is still unknown about how to optimize their energy density and reduce crossover rates. In this experiment, ultraviolet-visible spectrophotometry was used to quantify the crossover rate for a set of molecules varying in hydrophobicity, charge, and molecular weight. A novel, experimental setup allowed for the tracking of compounds across a Fumasep FAPQ-375-PP membrane over time. Acetonitrile with 100mM TBAPF6 was used as the electrolyte. Solutions with an initial concentration of 10 mM of each compound were inserted on one side of the membrane. From calibration curves and Beer’s Law, absorbance was related to concentration and the rate of crossover. From these data, a predictive mathematical model, with the potential to predict molecular structures with slower crossover rates, was developed. Presented at the 2018 ACCESS Symposium at the University of Utah.