Non-aqueous Redox Flow Batteries (NRFBs) are emerging devices for electric grid storage applications. A major challenge in redox flow batteries is enhancing the ionic conductivity across the membrane while preventing the crossover of the anolyte and catholyte . Recently, we reported that using redox active polymers (RAPs) in combination with size exclusion membranes, in contrast to ion selective membranes, provides a viable alternative that addresses these challenges and enables NRFBs.<br/>The electron transfer kinetics of large polymer redox mediators with hundreds to thousands of redox active centers in solution are not well understood. In addition, the existence of a preceding chemical step that mediates the redox chemistry of RAPs in solution highlights the importance of charge hopping on these polymer. In order to gain a better understanding of the electrochemical properties of RAPs, we use a systematic molecular design approach to investigate the impact of backbone and redox-pendant electronic interactions on the performance of viologen RAPs (fig. 1). We used different electrochemical techniques to study the redox properties, charge transfer kinetics and self-exchange of electrons through redox active dimers and their equivalent polymers. Stark contrast was observed between the electrochemical properties of viologen dimers and their corresponding polymers. Our studies provide insides on how the modulation of RAP inter-pendant interactions decisively impacts charge transfer. While polymers with optimized macroscopic reversibility were obtained, the microscopic trends describing small molecule electrochemistry did not hold for polymers, showing anti-Marcus effects that require further investigation.

Enhancing charge transport in redox active polymers through molecular design

253rd National Meeting (2017)

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