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Download fileNanoconfinement Effects on Enhanced Reversibility of Redox Reactions Coupled with an Irreversible Chemical Process by Electrolysis Acceleration in Nanoporous Carbon Electrodes for a Redox-Enhanced Electrochemical Capacitor
journal contribution
posted on 29.07.2020, 08:29 authored by Jaehyun Jeon, Jihye Lee, Kyu Yeon Jang, Hana Yoon, Jinho ChangRedox-enhanced
electrochemical capacitors (Redox-ECs) in which
electrons are stored and released by redox reactions of organic molecules
either dissolved in an electrolyte or adsorbed on an electrode surface
represent a promising energy storage system with electrochemical characteristics
of both rechargeable batteries and electrical double-layer capacitors.
However, the choices for redox-active molecules in Redox-ECs are often
limited due to an irreversible nature induced by chemical processes,
such as hydrolysis, coupled with e–-transfer reactions.
Here, we describe the effects of nanoconfinement on enhanced reversibility
in the redox reaction of an electroactive organic molecule undergoing
irreversible hydrolysis after e–-transfer in a nanoporous
carbon electrode. The redox reaction between hydrated rhodizonic acid
(RDZ·2H2O) and hexahydroxybenzene (HHB) via tetrahydroxy-1,4-benzoquinone
served as a model in which RDZ is irreversibly hydrolyzed to RDZ·2H2O. This phenomenon results from electrolysis acceleration
within confined nanoregimes in a porous carbon matrix, which is analyzed
by finite-element analysis. We built asymmetric ECs composed of nanoporous
carbon electrodes, one of which was coated with RDZ·2H2O. Due to the enhanced reversibility of the RDZ·2H2O/HHB redox reaction in a nanoporous carbon electrode, Coulombic
efficiency of the cell remained near 90% despite the irreversible
nature of RDZ via hydrolysis. This research provides fundamental insights
into the use of organic molecules in energy storage using redox electrolytes
such as Redox-ECs and organic redox flow batteries.