TY - JOUR
T1 - An SECM-Based Spot Analysis for Redoxmer-Electrode Kinetics
T2 - Identifying Redox Asymmetries on Model Graphitic Carbon Interfaces
AU - Gaddam, Raghuram
AU - Sarbapalli, Dipobrato
AU - Howard, Jason
AU - Curtiss, Larry A.
AU - Assary, Rajeev S.
AU - Rodríguez-López, Joaquín
N1 - This research was financially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, and Basic Energy Sciences. We thank Jamie Berry and the Denmark lab at UIUC for providing the ferrocenium hexafluorophosphate used in this study. We acknowledge central facilities at the Materials Research Laboratory, and the Beckman Institute, University of Illinois, for graphene growth, optical transmittance, XPS and Raman spectroscopy measurements. We thank Dr. Richard T. Haasch for acquiring the XPS spectra. We would like to thank the Laboratory Computing Resource Center (LCRC) faculty of Argonne National Laboratory for their support and maintenance, that made the DFT computations in this project possible. Additionally, we gratefully acknowledge the computing resources provided on “BEBOP”, a computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory (ANL).
This research was financially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, and Basic Energy Sciences. We thank Jamie Berry and the Denmark lab at UIUC for providing the ferrocenium hexafluorophosphate used in this study. We acknowledge central facilities at the Materials Research Laboratory, and the Beckman Institute, University of Illinois, for graphene growth, optical transmittance, XPS and Raman spectroscopy measurements. We thank Dr. Richard T. Haasch for acquiring the XPS spectra. We would like to thank the Laboratory Computing Resource Center (LCRC) faculty of Argonne National Laboratory for their support and maintenance, that made the DFT computations in this project possible. Additionally, we gratefully acknowledge the computing resources provided on “BEBOP”, a computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory (ANL).
PY - 2023/1/17
Y1 - 2023/1/17
N2 - The fundamental process in non-aqueous redox flow battery (NRFB) operation revolves around electron transfer (ET) between a current collector electrode and redox-active organic molecules (redoxmers) in solution. Here, we present an approach utilizing scanning electrochemical microscopy (SECM) to evaluate interfacial ET kinetics between redoxmers and various electrode materials of interest at desired locations. This spot-analysis method relies on the measurement of heterogeneous electron transfer rate constants (kf or kb) as a function of applied potential (E−E0′). As demonstrated by COMSOL simulations, this method enables the quantification of Butler-Volmer kinetic parameters, the standard heterogeneous rate constant, k0, and the transfer coefficient, α. Our method enabled the identification of inherent asymmetries in the ET kinetics arising during the reduction of ferrocene-based redoxmers, compared to their oxidation which displayed faster rate constants. Similar behavior was observed on a wide variety of carbon electrodes such as multi-layer graphene, highly ordered pyrolytic graphite, glassy carbon, and chemical vapor deposition-grown graphite films. However, aqueous systems and Pt do not exhibit such kinetic effects. Our analysis suggests that differential adsorption of the redoxmers is insufficient to account for our observations. Displaying a greater versatility than conventional electroanalytical methods, we demonstrate the operation of our spot analysis at concentrations up to 100 mM of redoxmer over graphite films. Looking forward, our method can be used to assess non-idealities in a variety of redoxmer/electrode/solvent systems with quantitative evaluation of kinetics for applications in redox-flow battery research.
AB - The fundamental process in non-aqueous redox flow battery (NRFB) operation revolves around electron transfer (ET) between a current collector electrode and redox-active organic molecules (redoxmers) in solution. Here, we present an approach utilizing scanning electrochemical microscopy (SECM) to evaluate interfacial ET kinetics between redoxmers and various electrode materials of interest at desired locations. This spot-analysis method relies on the measurement of heterogeneous electron transfer rate constants (kf or kb) as a function of applied potential (E−E0′). As demonstrated by COMSOL simulations, this method enables the quantification of Butler-Volmer kinetic parameters, the standard heterogeneous rate constant, k0, and the transfer coefficient, α. Our method enabled the identification of inherent asymmetries in the ET kinetics arising during the reduction of ferrocene-based redoxmers, compared to their oxidation which displayed faster rate constants. Similar behavior was observed on a wide variety of carbon electrodes such as multi-layer graphene, highly ordered pyrolytic graphite, glassy carbon, and chemical vapor deposition-grown graphite films. However, aqueous systems and Pt do not exhibit such kinetic effects. Our analysis suggests that differential adsorption of the redoxmers is insufficient to account for our observations. Displaying a greater versatility than conventional electroanalytical methods, we demonstrate the operation of our spot analysis at concentrations up to 100 mM of redoxmer over graphite films. Looking forward, our method can be used to assess non-idealities in a variety of redoxmer/electrode/solvent systems with quantitative evaluation of kinetics for applications in redox-flow battery research.
KW - COMSOL
KW - SECM
KW - binding energy
KW - carbon
KW - electron transfer
KW - ferrocene
KW - graphene
KW - kinetics
KW - redox-flow battery
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U2 - 10.1002/asia.202201120
DO - 10.1002/asia.202201120
M3 - Article
C2 - 36482038
AN - SCOPUS:85144979164
SN - 1861-4728
VL - 18
JO - Chemistry - An Asian Journal
JF - Chemistry - An Asian Journal
IS - 2
M1 - e202201120
ER -