Kinetics of film-coated electrodes

Leddy, Johna; Bard, Allen J.; Maloy, J. T.; Savéant, Jean‐Michel

doi:10.1016/0368-1874(85)85779-8

Cited by 121 publications

(63 citation statements)

References 39 publications

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“…RDE is useful for calculating the diffusion coefficients (D), electron transfer rate constants (k f ) and standard rate constants (k 0 ) via Levich and Koutecky-Levich equations which are shown in Supporting Information ( Figure S21). 22,23 Previously, we have reported that viologen-based RAPs display adsorption at metal electrodes. Charge hopping via self-exchange reactions likely take place between the RAP film on the electrode and solution RAPs, 24 as well as within individual RAPs.…”

Section: Resultsmentioning

confidence: 99%

Scanning Electrochemical Microscopy and Hydrodynamic Voltammetry Investigation of Charge Transfer Mechanisms on Redox Active Polymers

Burgess

Hernández‐Burgos

Simpson

et al. 2015

J. Electrochem. Soc.

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We recently showed that viologen-based redox active polymers (RAPs) with molecular weights between 21 and 318 kDa are attractive charge storage materials as anolytes for size-selective non-aqueous redox flow batteries. Here, we characterize the electron transfer mechanisms of these RAPs, as well as a ferrocene based catholyte RAP, in acetonitrile/Li + electrolyte. We utilized scanning electrochemical microscopy (SECM) and rotating disk electrode (RDE) voltammetry to measure the rate of electron transfer and the rate of charge hopping between neighboring pendants along the insulating backbone of RAPs. The electron transfer kinetics of a 271 kDa ferrocene RAP mimic the facile kinetics of its monomer repeating unit. In contrast, viologen RAPs displayed RDE and SECM signatures that suggest a preceding chemical step to electron transfer. Viologen RAPs adsorb strongly to the electrode surface and create a redox active film that controls the rate of electron transfer via self-exchange. In addition, finite element simulations including a preceding chemical step demonstrated that a purely mass-transfer limited model is insufficient to recreate the viologen RAP feedback SECM response. Non-aqueous redox flow batteries (NRFBs) are emerging technologies for electrical energy storage, and are an attractive alternative to their aqueous counterparts. [1][2][3][4][5][6] The choice of organic solvents with voltage windows larger than that required for the electrolysis of water enables the use of a larger variety of redox molecules and electrolyte systems, where the combination of high solubility and higher reaction potentials leads to increased energy density. A major challenge in NRFBs is to increase the conductivity of the electrolyte through the commonly used ion exchange membrane. In response to this challenge, our groups recently reported on a new size-selective concept in flow batteries where a porous separator replaces poorly performing ion exchange membranes.7-9 These porous separators are coupled to high energy density redox active polymers (RAPs) that replaced small molecules as charge storage media. RAPs consist of an unconjugated polymer backbone densely decorated with redox active pendants. We previously reported on the electrochemical characterization of viologen-based RAPs with molecular weight between 21 and 318 kDa, which displayed hydrodynamic radii between 4 and 7 nm. Increasing the size of RAPs decreased transport through Celgard which was used as a porous separator. However, we are also interested in understanding the impact of size on the rate and mechanisms of charge transfer and transport on RAPs to determine their ultimate performance limit. 10RAPs displayed attractive electrochemical properties such as similar standard reduction potentials than those of the parent monomer, efficient bulk electrolysis with up to +98% of redox groups reversibly accessible, and high solubility of up to 2.8 M with quantitative electrode reactivity even when at 1.0 M. Despite these promising features, little is known about el...

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Section: Resultsmentioning

confidence: 99%

Scanning Electrochemical Microscopy and Hydrodynamic Voltammetry Investigation of Charge Transfer Mechanisms on Redox Active Polymers

Burgess

Hernández‐Burgos

Simpson

et al. 2015

J. Electrochem. Soc.

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“…Membrane-permeation rate through poly-ionic films was found [15,18] dependent on the permeant charge and molecular size. Different permeability to neutral versus charged electroactive solutes can also be exhibited by nonionic films [12?1 j].…”

Section: Discussionmentioning

confidence: 97%

“…at least, with the pinhole size lower than the molecular dimension of the monomer. On these grounds, interpretation of results can be done b,; models for membrane permeation [16][17][18]. The alternative ap- proach of infinitesimally small channel transport is mathematically equivalent [ 191.…”

Section: Discussionmentioning

confidence: 99%

Permeation of solutes through an electropolymerized ultrathin poly‐o‐phenylenediamine film used as an enzyme‐entrapping membrane

et al. 1994

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Permeation of electroactive organic probes through an electroinactive and passivating poly-ophenylenediamine (PPD) film electropolymerized on Pt and glassy carbon (GC) electrodes has been investigated by cyclic and rotating disk electrode (RDE) voltammetry. The access of solutes to the metal-polymer interface appears mainly governed by specific chemical interactions, influencing partition, and diffusion phenomena, rather than by exclusion effects based on molecular size or charge. Potential cycling of the film induces fine modifications in the chemical/physical structure of the polymer, as evidenced by electron spectroscopy for chemical analysis (ESCA) measurements and by an enhanced permeation of certain solutes. The membrane is, however, stable in the pH and potential range usually employed in its application, that is, as an enzyme-entrapping membrane in amperometric biosensors; because of membrane permselectivity, the electrochemical response of the most common electroactive interferents is deeply depressed.

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“…19,[24][25][26][27][28][29][30][31][32] Other literature reports for single, incompressible layers include clay and nanostructured clay composites, emulsion polymers and copolymers, latex, and redox polymers (where the redox potential of the probe is well separated from the electroactive monomer). Cases where R interface > 0 are discussed below.…”

Section: Models For Uniform Filmsmentioning

confidence: 99%

Film Permeation by Rotating Disk Voltammetry at Electrodes Modified with Electrochemically Inert Layers and Heterogeneous Composites

Knoche

Hettige

Zook-Gerdau

et al. 2016

J. Electrochem. Soc.

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Steady state rotating disk voltammetry provides excellent measurement of permeability for films and layers on electrodes because the hydrodynamic control of rotating disks establishes well defined boundary layers normal to the electrode. For a redox probe present in solution and pre-equilibrated in the layer, voltammetry measures electrolysis current for the probe as the probe transports from solution, through the film, and to the electrode where the probe is electrolyzed. Diagnostic equations relate the steady state, mass transport limited current iss to the rotation rate ω. The incompressible layer is electroinactive about the probe formal potential. Diagnostics are available for a single layer, uniform film (Gough and Leypoldt). Uniform films are homogeneous with no structural features. Here diagnostics are provided for bilayer and multilayer uniform films, where multilayers include discretely and continuously graded films. Consideration of serial mass transport resistances normal to the electrode allows diagnostics for uniform films. Heterogeneous, micro- and nano-structured layers are structured in the plane of the electrode. Consideration of parallel mass transport resistances as part of the layer mass transport resistance yields diagnostics for heterogeneous films. Diagnostics are vetted with literature data. Theoretical and practical advantages and limitations are noted.

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Kinetics of film-coated electrodes

Cited by 121 publications

References 39 publications

Scanning Electrochemical Microscopy and Hydrodynamic Voltammetry Investigation of Charge Transfer Mechanisms on Redox Active Polymers

Scanning Electrochemical Microscopy and Hydrodynamic Voltammetry Investigation of Charge Transfer Mechanisms on Redox Active Polymers

Permeation of solutes through an electropolymerized ultrathin poly‐o‐phenylenediamine film used as an enzyme‐entrapping membrane

Film Permeation by Rotating Disk Voltammetry at Electrodes Modified with Electrochemically Inert Layers and Heterogeneous Composites

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