The electrochemical quartz crystal microbalance

The electrochemical quartz crystal microbalance (EQCM) has emerged as a very powerful in situ technique to complement electrochemical experiments [3-5]. Nomura and Okuhara [15] first used the quartz crystal microbalance (QCM) to detect mass changes at a metal coated quartz resonator immersed in electrolyte during electrochemical experiments. 

The technique has been extended to other electrochemical phenomena such as electro-deposition and dissolution of metal films, hydrogen absorption in metals, under-potential deposition, electrolyte adsorption, and ion and solvent exchange in redox polymer layers and electrochemically driven self-assembly, etc. [5]. 

The EQCM has been most commonly used simultaneously to quasisteady state techniques like slow scan cyclic voltammetry. In this way mass changes during electrolysis can be obtained from A/(Am/.4) vs. potential curves, while A/(AmA4) vs. charge density curves allow evaluation of the number of Faraday exchanged per mole of electro-active species by use of Faraday s law of electrolysis. 

Kinetic applications of the electrochemical quartz crystal microbalance Ch. 12 

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The electrochemical quartz crystal microbalance (EQCM) is a powerful tool for elucidating interfacial reactions based on the simultaneous measurement of electrochemical parameters and mass changes at electrode surfaces. The microbalance is based on a quartz crystal wafer, which is sandwiched between two electrodes, used to induce an electric field (Figure 2-20). The field produces a mechanical oscillation... 

The electrochemical quartz crystal microbalance (EQCM) is a very useful technique for detecting small mass changes at the electrode surface that accompany electrochemical processes. In 1880, Jacques and Pierre Curie discovered that when stress was applied to some crystals, such as quartz, it resulted in an electrical potential across the... 

Ward, M. D., Principles and applications of the electrochemical quartz crystal microbalance, in Physical Electrochemistry, I. Rubenstein, Ed., Marcel Dekker, New York, 1995, p. 293. 

The Electrochemical Quartz Crystal Microbalance d 2.2.7—FTIR and Related Techniques... 

The electrochemical quartz crystal microbalance (EQCM) method was first used to study underpotential deposition in 1988 for Pb, Bi, Cu,... 

A technique for such measurements is the electrochemical quartz crystal microbalance (EQCM figure 14) [71]. Here, the working electrode is part of a quartz crystal oscillator that is mounted on the wall of the electrochemical cell and exposed to the electrolyte. The resonance frequency / of the quartz crystal is proportional to mass changes Am A/ Am. With base frequencies around 10 MHz, the determination of Am in the ng range is possible. 

Analytical Applications of the Electrochemical Quartz Crystal Microbalance... 

The Electrochemical Quartz Crystal Microbalance (EQCM) The resonant frequency of a quartz crystal oscillator is perturbed from its base value (f ) by attached overlayers. For thin, rigid films the measured change in resonant frequency (Af) with attached mass (AM) is described by the Sauerbrey equation (10) ... 

The strong dependence of the layer structure on the nature of the contacting electrolyte has been further investigated by using the electrochemical quartz crystal microbalance (EQCM). As discussed above in Chapter 3, this technique is based on the measurement of the frequency with which a coated quartz crystal vibrates, and this frequency can then be related to the mass of this crystal provided that the material attached to the surface is rigid. In this way, the changes that occur in thin films as a result of redox processes can be monitored. 

Buttry, D.A. Ward, M.D. Measurement of interfacial processes at electrode surfaces with the electrochemical quartz crystal microbalance. Chem. Rev. 1992, 92, 1355-1379. 

Since the early work of Kanazawa [1] and Bruckenstein in 1985 [2], quartz crystal resonators have been used for more than 12 years in contact with liquids to assess changes in mass during electrochemical surface processes. Extensive use of the electrochemical quartz crystal microbalance (EQCM) has been done in the study of electrode processes with change of mass simultaneous to charge transfer. 

Buttry [47] measured the admittance around resonance of a quartz crystal coated with polynitrostyrene and related those measurements to the rheological changes due to film swelling. Muramatsu et al. used the resonant resistance in addition to the resonant frequency of the electrochemical quartz crystal microbalance (EQCM) as a criterion to evaluate the film non-rigidity for several electroactive polymer systems [6], including... 

Our approach to this problem involves a detailed mechanistic study of model systems, in order to identify the (electro)chemical parameters and the physicochemical processes of importance. This approach takes advantage of one of the major developments in electrochemical science over the last two decades, namely the simultaneous application of /ton-electrochemical techniques to study interfaces maintained under electrochemical control [3-5]. In general terms, spectroscopic methods have provided insight into the detailed structure at a variety of levels, from atomic to morphological, of surface-bound films. Other in situ methods, such as ellipsometry [6], neutron reflectivity [7] and the electrochemical quartz crystal microbalance (EQCM) [8-10], have provided insight into the overall penetration of mobile species (ions, solvent and other small molecules) into polymer films, along with spatial distributions of these mobile species and of the polymer itself. Of these techniques, the one upon which we rely directly here is the EQCM, whose operation and capability we now briefly review. 

The electrochemical quartz crystal microbalance is a versatile technique for studying several aspects of electroactive polymer film dynamics. For rigid films, it is a sensitive probe of mobile species (ion and solvent) population changes within the film in response to redox switching. For non-rigid films, it can be used to determine film shear moduli. In the former case, one simply follows changes in crystal resonant frequency. In the latter case, the frequency dependence of resonator admittance in the... 

Biosens Bioelectron 14 663 [v] HepelM (1999) Electrode-solution interface studied with electrochemical quartz crystal nanobalance. In Wieczkowski A (ed) Interfacial electrochemistry. Marcel Dekker, New York, pp 599-630 [vi] Hillman AR (2003) The Electrochemical quartz crystal microbalance. In Bard AJ, Stratmann M, Unwin PR (eds) Instrumentation and electroanalytical chemistry. Encyclopedia of electrochemistry, vol. 3. Wiley-VHC, Weinheim, pp 230-289 [vii] Tsionsky V, Daikhin L, Urbakh M, Gileadi E (2004) Looking at the metal/solution interface with electrochemical quartz-crystal microbalance Theory and experiment. In Bard AJ, Rubinstein I (eds) Electroanalytical chemistry, vol 22. Marcel Dekker, New York, pp 2-94 [viii] Vilas-Boas M, Henderson MJ, Freire C, Hillman AR, Vieil E (2000) Chem Eur / 6 1160 [ix] Inzelt G, Horanyi G (1989) / Electrochem Soc 136 1747 [x] Gollas B, Bartlett PN, Denuault (2000) Anal Chem 72 349 [xi] Gabrielli C, Ked-dam M, Perrot H, Torresi R (1994) ] Electroanal Chem 378 85... 

PPy films modified by platinum catalyst particles were also considered for electrocatalytic reactions (oxygen reduction and methanol oxidation) by Hepel et al. [41], The incorporation of a PtCl anion was performed during the electropolymerization of pyrrole and monitored by the electrochemical quartz crystal microbalance (EQCM) technique, allowing us to evaluate the amount of platinum obtained after reduction of the PPy/PtCl film. 

A system developed recently sheds further light on these dynamic processes. The technique is the electrochemical quartz crystal microbalance (EQCM), wherein the polymer is deposited on a gold-coated quartz crystal. Changes in polymer mass, as the polymer is electrochemically reduced or oxidized, can then be monitored in situ,144 145 For example, as the polymer is reduced, anion removal is indicated by the change in mass observed, as shown in Figure 1.23b. This technique has proved particularly useful for the study of complex systems, e.g., those containing polyelectrolytes, wherein cation movement rather than anion predominates, and this is reflected in increases in mass at negative potentials. 

Tsionsky V, Daikhin L, Urbakh M, Gileadi E (2003) Looking at the metal/solution interface with the electrochemical quartz crystal microbalance, theory and experiment. In Bard AJ, Rubinstein I (eds) Electroanalytical chemistry. Dekker, New York, P 1... 

Hillman AR (2003) The electrochemical quartz crystal microbalance. In Bard AJ (ed) Encyclopedia of electrochemistry. Wiley, Weinheim, p 230 Sauerbrey G (1959) Z Phys 155 206... 

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