Electrochemical Impedance Spectroscopy Optimization on Passive Metals

Engelhardt, George R.; Case, Raymundo; Macdonald, Digby D.

doi:10.1149/2.0811608jes

Cited by 29 publications

(12 citation statements)

References 14 publications

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“…Similarly, the shift from a higher to a lower frequency at which the dip in the phase angle (Bode plot in Figure d) appears is an indication of a slower electron transfer kinetics with exposure time. Full description of the impedance spectra can be found in previous literature studies. − The equivalent circuit used to fit the EIS data is shown in Figure S7 (Supporting Information). The k et value decreases with the waiting time (Figure e).…”

Section: Results and Discussionmentioning

confidence: 99%

Nanoscale Silicon Oxide Reduces Electron Transfer Kinetics of Surface-Bound Ferrocene Monolayers on Silicon

Dief

Lyu

et al. 2021

J. Phys. Chem. C

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Functionalizing Si with self-assembled monolayers (SAMs) paves the way for integrating the semiconducting properties of Si with the diverse properties of organic molecules. Highly packed SAMs such as those formed from alkyl chains protect Si from reoxidation in an ambient environment. Such monolayers have been largely considered oxide-free, but the effect of nanoscale reoxidation on the electrochemical kinetics of Si-based SAMs remains unknown. Here, we systematically study the effect of the oxide growth on the electrochemical charge-transfer kinetics of ferrocene-terminated SAMs on Si by exposing the surfaces to ambient conditions for controlled periods of time. X-ray photoelectron spectroscopy and atomic force microscopy revealed a gradual growth of silicon oxide (SiO x ) on the surfaces over time. The oxide growth is accompanied by a decrease in the ferrocene surface coverage and a concomitant decrease in the electron transfer rate constant (k et) measured by electrochemical impedance spectroscopy. The drop in k et is attributed to a greater spacing between the ferrocene moieties induced by the surface oxide, which in turn blocks lateral electron transfer between neighboring ferrocene moieties. These findings explain the highly scattered literature data on electron transfer kinetics for monolayers on Si and have implications for the proper design of Si-based molecular electronic devices.

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Section: Results and Discussionmentioning

confidence: 99%

Nanoscale Silicon Oxide Reduces Electron Transfer Kinetics of Surface-Bound Ferrocene Monolayers on Silicon

Dief

Lyu

et al. 2021

J. Phys. Chem. C

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“…The electrical contact between the Si and the copper plate was reached by rapidly rubbing gallium indium eutectic on the back side of the Si electrode. EIS measurements were carried out at a DC offset equal to the half-wave potential ( E 1/2 ) measured in the CV experiments. ,− The AC amplitude was 15 mV, and the frequency was scanned between 1 and 100,000 Hz. The surface coverages (Γ) of ferrocene molecules were calculated from the integration of the CV oxidation and reduction waves according to Γ = Q / nFA (where Q is the charge, n is the number of electron transfer, F is Faraday constant, and A is the area of electrode).…”

Section: Methodsmentioning

confidence: 99%

On-Surface Azide–Alkyne Cycloaddition Reaction: Does It Click with Ruthenium Catalysts?

Dief

Kalužná

et al. 2022

Langmuir

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Owing to its simplicity, selectivity, high yield, and the absence of byproducts, the “click” azide–alkyne reaction is widely used in many areas. The reaction is usually catalyzed by copper(I), which selectively produces the 1,4-disubstituted 1,2,3-triazole regioisomer. Ruthenium-based catalysts were later developed to selectively produce the opposite regioselectivity—the 1,5-disubstituted 1,2,3-triazole isomer. Ruthenium-based catalysis, however, remains only tested for click reactions in solution, and the suitability of ruthenium catalysts for surface-based click reactions remains unknown. Also unknown are the electrical properties of the 1,4- and 1,5-regioisomers, and to measure them, both isomers need to be assembled on the electrode surface. Here, we test whether ruthenium catalysts can be used to catalyze surface azide–alkyne reactions to produce 1,5-disubstituted 1,2,3-triazole, and compare their electrochemical properties, in terms of surface coverages and electron transfer kinetics, to those of the compound formed by copper catalysis, 1,4-disubstituted 1,2,3-triazole isomer. Results show that ruthenium(II) complexes catalyze the click reaction on surfaces yielding the 1,5-disubstituted isomer, but the rate of the reaction is remarkably slower than that of the copper-catalyzed reaction, and this is related to the size of the catalyst involved as an intermediate in the reaction. The electron transfer rate constant ( k et ) for the ruthenium-catalyzed reaction is 30% of that measured for the copper-catalyzed 1,4-isomer. The lower conductivity of the 1,5-isomer is confirmed by performing nonequilibrium Green’s function computations on relevant model systems. These findings demonstrate the feasibility of ruthenium-based catalysis of surface click reactions and point toward an electrical method for detecting the isomers of click reactions.

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“…Then, the diffusion impedance may be omitted, and the charge transfer resistance combined with other contributing resistances yielding an overall apparent resistance R app with a model, as shown in Fig. 1(c) [36], [37].…”

Section: A Electrode-electrolyte Interface Impedancementioning

confidence: 99%

“…1. EEI equivalent circuits (a) adapted from Randles [32], (b) adapted from Córdoba-Torres et al [35], and (c) adapted from Engelhardt et al [37].…”

mentioning

confidence: 99%

Equivalent Circuit Models for Soils and Aqueous Solutions Under 2-Terminal Test Configuration

Desai

Harid

Griffiths

et al. 2023

IEEE Trans. Electromagn. Compat.

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Numerous circuit models have been proposed to represent the electrode-electrolyte interface (EEI) impedance and bulk medium impedance of conducting media. Following a review, two suitable models are constructed to represent the behavior of conduction in electrolytes and soils, respectively. Both models incorporate a constant phase element in parallel with an apparent Faradaic resistance, which is found to reproduce the EEI behavior accurately. For the electrolyte model, a single parallel R-C branch is added to represent the impedance of the bulk medium, whereas for the soil model, an equivalent ladder network of R-C branches is found to be suitable. Experimentally obtained electrolyte and soil impedance data based on 2-terminal impedance spectroscopy over a frequency range of 10 mHz to 10 MHz with variable current density are compared with values obtained from the models and where model parameters are determined by a curve fitting routine. The effects of electrolyte concentration, soil moisture, and electrode material are analyzed, and the models help to illustrate clearly how the EEI effect dominates at low frequencies while the intrinsic characteristics of the test medium prevails at high frequencies. The models are extended to account for soil-electrolyte impedance dependence on current density, which is most evident at low frequencies. The extent of the impedance plateau region is described by limiting upper and lower frequencies.

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Electrochemical Impedance Spectroscopy Optimization on Passive Metals

Cited by 29 publications

References 14 publications

Nanoscale Silicon Oxide Reduces Electron Transfer Kinetics of Surface-Bound Ferrocene Monolayers on Silicon

Nanoscale Silicon Oxide Reduces Electron Transfer Kinetics of Surface-Bound Ferrocene Monolayers on Silicon

On-Surface Azide–Alkyne Cycloaddition Reaction: Does It Click with Ruthenium Catalysts?

Equivalent Circuit Models for Soils and Aqueous Solutions Under 2-Terminal Test Configuration

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