Visualization of energy transfer among redox active polymeric colloids via in-situ fluorescence microscopy
The increasing contribution of intermittent renewable energy sources to the electrical grid is resulting in energy storage becoming more and more crucial to both improve grid stability and to enable increasing penetration of renewable in electrical generation. There are numerous number of technologies being considered for that purpose and redox flow batteries are considered one of the most promising designs for stationary energy storage due to their scalability, high-efficiency and decoupled control of energy and power. To prevent the crossover of energy carriers between anolyte and catholyte compartments of the flow battery, as one example, the redox active ethyl viologen agent has been covalently bound within crosslinked polymeric colloids. Little is currently known about how electrons (energy) transfers either within or between redox active colloids (RAC). To elucidate this, contact-mediated electron transfer between these redox active colloids (RAC) was characterized via confocal microscope using the intrinsic redox state-dependent electrofluorochromism of the RACs as the readout of the charge state of individual colloids. Via this approach, it was possible to map the redox-state of the system. By means of coupling a distinct fluorescent contrast with the respective redox state, intra- and inter- colloid energy transfer processes were reversibly imaged in situ, during electrochemical cycling. A three electrode in-situ cell setup was used for the cycling in which a Pt electrode used as the working electrode, carbon was used as the counter electrode and Ag/AgCl was used as the reference electrode. The system also showed a considerably increased sensitivity to fluorescence quenching. Investigation of the amplified sensitivity was done and this was attributed to fast electron hopping among neighboring redox groups.
Redox Active Colloids, Electrochemistry, Energy transfer, Flow Battery
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign