EQCM electrochemical quartz-crystal

The first application of the quartz crystal microbalance in electrochemistry came with the work of Bruckenstein and Shay (1985) who proved that the Sauerbrey equation could still be applied to a quartz wafer one side of which was covered with electrolyte. Although they were able to establish that an electrolyte layer several hundred angstroms thick moved essentially with the quartz surface, they also showed that the thickness of this layer remained constant with potential so any change in frequency could be attributed to surface film formation. The authors showed that it was possible to take simultaneous measurements of the in situ frequency change accompanying electrolysis at a working electrode (comprising one of the electrical contacts to the crystal) as a function of the applied potential or current. They coined the acronym EQCM (electrochemical quartz crystal microbalance) for the technique. 

An electrochemical quartz crystal microbalance (EQCM or QCM) can be used to estimate the surface roughness of deposited lithium [43],... 

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... 

Such approximation is valid when the thickness of the polymeric layer is small compared to die thickness of die crystal, and the measured frequency change is small with respect to the resonant frequency of the unloaded crystal. Mass changes up to 0.05% of die crystal mass commonly meet this approximation. In die absence of molecular specificity, EQCM cannot be used for molecular-level characterization of surfaces. Electrochemical quartz crystal microbalance devices also hold promise for the task of affinity-based chemical sensing, as they allow simultaneous measurements of both tile mass and die current. The principles and capabilities of EQCM have been reviewed (67,68). The combination of EQCM widi scanning electrochemical microscopy has also been reported recently for studying die dissolution and etching of various thin films (69). The recent development of a multichannel quartz crystal microbalance (70), based on arrays of resonators, should further enhance die scope and power of EQCM. 

In the case of Ni(OH)2 and conductive polymer electrodes, solvent and anions intercalate into the electrode at anodic potentials. Electrochemical quartz crystal microbalance (EQCM) is a useful technique for monitoring the ingress and egress of solvent and anions in these materials. 

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... 

Electrochemical Quartz Crystal Microbalance Fntnre advances will require the coupling of EQCM with spectroscopic techniqnes that yield chemical information. EQCM has been conpled with ellipsometry (Gottesfeld et al., 1995). However, ellip-sometry does not yield chemical information. 

We have found new CO-tolerant catalysts by alloying Pt with a second, nonprecious, metal (Pt-Fe, Pt-Co, Pt-Ni, etc.) [Fujino, 1996 Watanabe et al., 1999 Igarashi et al., 2001]. In this section, we demonstrate the properties of these new alloy catalysts together with Pt-Ru alloy, based on voltammetric measurements, electrochemical quartz crystal microbalance (EQCM), electrochemical scanning tunneling microscopy (EC-STM), in situ Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). 

An application of an electrochemical quartz crystal microbalance (EQCM) in the study of the A11/HCIO4 system shows that even at a potential about 0.5 V more negative than the onset of AuO formation (the so-called preoxide region), the resonant frequency of the Au-covered quartz crystal decreases as that of the surface mass increases. A comparison of a voltammogram with the potential dependence of the micro-balance frequency for an Au electrode is shown in Figs. 6a and 6b. 

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. 

Electrochemical quartz crystal microbalance (EQCM) has been used [65] to study adsorption/desorption of iodide on Au(lll) electrodes. The coverages obtained at different potentials were quite close to those estimated from STM images and SXS measurements. 

Pb UPD on polycrystalline An electrode in 0.1 M perchloric acid solution has been studied by Henderson et al. [484]. In this study, CV, electrochemical quartz crystal microbalance (EQCM), and probe beam deflection methods have been used. It has been found that Pb UPD proceeds in three steps. The first step comprised water ejection from the gold surface. This step was followed by metal UPD accompanied by the removal of the adsorbed OH. Also, Zeng and Bruckenstein have studied UPD and adsorption of Pb on pc-Au electrodes, applying XPS and TOF-SIMS method in case of 0.1 M NaCl electrolyte [485], and EQCM in case of 0.1 M NaCl04 and 0.1 M NaCl electrolytes [486]. In the presence of chloride anions, the adsorption of Pb—Cl complex has been found. 

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