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High electrocatalytic performance of N and O atomic co-functionalized carbon electrodes for vanadium redox flow battery.

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Title: High electrocatalytic performance of N and O atomic co-functionalized carbon electrodes for vanadium redox flow battery.
Authors: Kim, Jiyeon1, Lim, Hyebin1, Jyoung, Jy-Young2, Lee, Eun-Sook2, Yi, Jung S.3, Lee, Doohwan1 dolee@uos.ac.kr
Source: Carbon. Jan2017, Vol. 111, p592-601. 10p.
Subjects: Carbon electrodes, Electrocatalysis, Vanadium, Oxidation-reduction reaction, Ammoxidation, Chemical kinetics
Abstract: The effects of nitrogen and oxygen atomic co-functionalization of graphite felt (GF) by ammoxidation reactions for the positive and negative electrodes of vanadium redox flow battery (VRFB) are investigated. Ammoxidative surface reactions of the pristine-GF with NH 3 /O 2 results in effective N and O co-doping dominantly with kinetically relevant N and O functional groups; pyrrolic-N, pyridinic-N, and hydroxyl with high site densities. The intrinsic rate measurements reveal that the N and O co-functionalized GF electrodes (referred to as N-GF) afford one to several orders magnitude higher VO 2+ /VO 2 + and V 2+ /V 3+ redox kinetics than the pristine-GF. Notably, the N and O co-functionalization gives rise to 2–3 folds greater reaction kinetics for both half-cell reactions than the conventional electrodes doped only with O functional groups (O-GF) at similar atomic contents. The high electrocatalytic properties of N-GF afford 4–6% greater voltage and energy efficiencies in VRFB than the conventional O-GF electrode at high current density (110 mA cm −2 ) with ∼38% higher initial charge-discharge capability owing to the significantly reduced overpotential. These results suggest the marked synergetic contributions of N and O co-functionalization of carbon electrode for facilitation of vanadium redox kinetics and the high effectiveness of the simple and scalable ammoxidation-based functionalization protocol. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The effects of nitrogen and oxygen atomic co-functionalization of graphite felt (GF) by ammoxidation reactions for the positive and negative electrodes of vanadium redox flow battery (VRFB) are investigated. Ammoxidative surface reactions of the pristine-GF with NH 3 /O 2 results in effective N and O co-doping dominantly with kinetically relevant N and O functional groups; pyrrolic-N, pyridinic-N, and hydroxyl with high site densities. The intrinsic rate measurements reveal that the N and O co-functionalized GF electrodes (referred to as N-GF) afford one to several orders magnitude higher VO 2+ /VO 2 + and V 2+ /V 3+ redox kinetics than the pristine-GF. Notably, the N and O co-functionalization gives rise to 2–3 folds greater reaction kinetics for both half-cell reactions than the conventional electrodes doped only with O functional groups (O-GF) at similar atomic contents. The high electrocatalytic properties of N-GF afford 4–6% greater voltage and energy efficiencies in VRFB than the conventional O-GF electrode at high current density (110 mA cm −2 ) with ∼38% higher initial charge-discharge capability owing to the significantly reduced overpotential. These results suggest the marked synergetic contributions of N and O co-functionalization of carbon electrode for facilitation of vanadium redox kinetics and the high effectiveness of the simple and scalable ammoxidation-based functionalization protocol. [ABSTRACT FROM AUTHOR]
ISSN:00086223
DOI:10.1016/j.carbon.2016.10.043