Organo-disulfide-based particles enable controlled stimulus-triggered cleaning of electrode surfaces†

Abstract

Electrode fouling resulting in reduced performance is an ongoing challenge in electrochemical flow cells based on redox active polymers (RAPs). An avenue that holds substantial promise yet remains relatively unexplored involves the strategic design of RAPs capable of undergoing electrochemical stimulation to facilitate in situ electrode cleaning within a flow cell. Herein, a new electrode cleaning strategy is demonstrated through the application of redox-active poly(glycidyl methacrylate) particles crosslinked with 2-amino-1,3,4-thiadiazole disulfide (PGMA–ATDDS). The resulting particles can de-crosslink through cleavage of the disulfide bond using stimuli, such as electrochemical reduction or UV photoexcitation. Using a custom flow cell, applying such a stimulus to an ITO electrode artificially fouled with PGMA–ATDDS in the presence of a fluid flow leads to a significant particle removal (80%) that is over six times more efficient relative to the case when no stimulus is applied. Confocal fluorescence imaging of the electrochemically stimulated electrode highlighted localized disulfide reduction of particles near the electrode surface. It is posited that this selective de-crosslinking and concomitant electrolyte swelling at the particle/electrode interface facilitate particle removal in the presence of a fluid flow. In addition, the regeneration of electrode performance upon cleaning was demonstrated through charging of a redox-active particle suspension of poly(vinylbenzyl chloride) functionalized with dimethylaminoferrocene (PVBC–Fc). Upon electrochemical cleaning of the fouled ITO electrode, the accessible charge of PVBC–Fc was statistically equivalent to the accessible charge measured using a pristine ITO electrode. Overall, this study introduces a new approach for leveraging stimulus-responsive chemistries for RAPs to impart inherent functionality to facilitate in-line electrode cleaning in electrochemical flow cells.