(Invited) The Impact of Polyelectrolyte Dynamics on the Electrochemical Reactivity of Soluble Redox-Active Polymers

In this presentation, I will discuss recent findings regarding the impact of polyelectrolyte dynamics on the charge percolation and electrolysis efficiency of soluble Redox-Active Polymers (RAPs). RAPs[1] and their colloidal form (RACs)[2] are a new class of materials for energy storage in fluid dispersions for a novel concept in size-exclusion flow batteries.[3] Despite RAPs displaying excellent charge storage properties, their complex electrochemical reactive pathways are just becoming elucidated. RAPs and RACs rely on intra-particle electron transfer to yield quantitative charge accessibility and high rate in order to achieve full electrolysis.[4] Charge mobility via inter-pendant electron hopping combines with their polyelectrolyte nature to exhibit a rich electrochemical behavior that is strongly modulated by specific and non-specific interactions with the electrolyte. In this talk, I will highlight the impact of several variables on the electrochemical signatures created by RAPs and RACs. The mechanistic characterization of RAPs and RACs requires a spectrum of powerful electrochemical techniques, ranging from bulk methods to single-particle analysis. I will describe how the application of nano-resolved electrochemical microscopy techniques and Raman spectroscopy has helped us understand the mechanisms of individual electrochemical entities. These experiments provide us with unprecedented versatility to identify kinetic bottlenecks, such as charge trapping, and to determine the maximum current densities attainable in flow devices. Altogether, the combination of novel structural motifs, the identification of structure-reactivity relationships, and the use of advanced electrochemical techniques, results in new directions to make better polymers for a new concept in redox flow batteries. [1] J. Am. Chem. Soc. 2014, 136, 16309. [2] J. Am. Chem. Soc. 2016, 138, 13230. [3] Acc. Chem. Res. 2016, 49, 2649. [4] Chem. Mater. 2016, 28, 7362. *This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.