Reference electrode, vibrating

Fig. V-17. Schematic diagram for the apparatus for measurement of Vobs (see text). The vibrating reference electrode is positioned close to the surface of a AgN03 solution in which there is an Ag electrode, which, in turn, is in electrical contact with the reference electrode. (From Ref. 196.)...

The apparatus consists of a tip-position controller, an electrochemical cell with tip, substrate, counter and reference electrodes, a bipotentiostat and a data-acquisition system. The microelectrode tip is held on a piezoelectric pusher, which is mounted on an inchwomi-translator-driven x-y-z tliree-axis stage. This assembly enables the positioning of the tip electrode above the substrate by movement of the inchwomi translator or by application of a high voltage to the pusher via an amplifier. The substrate is attached to the bottom of the electrochemical cell, which is mounted on a vibration-free table [, and ]. A number... 

A 9 cm-1 upshift of the tangential mode (G band) vibrational frequency as well as a 90% decrease in intensity was observed by applying 1.0 V between an individual nanotube and a silver reference electrode in a dilute sulfuric acid solution. 

While the first STM studies of electrode surfaces were performed with self-built instruments, scanning tunneling microscopes for electrochemical use are nowadays commercially available at a price, which hardly justifies the effort of homemade equipment. Nevertheless, new instrumental designs are now and then discussed in the literature, which are still worthwhile to be considered for special applications. There is, however, additional equipment required for the operation of an electrochemical STM, for which homemade designs may be advantageous over commercially available ones and hence, is briefly mentioned here This refers to vibration damping, tip preparation and isolation, and the electrochemical cell. 

Figure 7 shows SNIFTIRS spectra for isoquinoline molecules adsorbed on mercury. The reference spectrum in each case was obtained at 0.0V vs. a SCE reference electrode at this potential the molecules are believed to be oriented flat on the metal surface. The vibrational frequencies of the band structure (positive values of absorbance) are easily assigned since they are essentially the same as those reported by Wait et al. (22) for pure isoquinoline. The differences in the spectra are that the bands for the adsorbed species exhibit blue shifting of 3-4 cm" relative to those of the neat material, and the relative intensities of the bands for the adsorbed species are markedly changed. 

Hackerman and Lee (83) have also used the simple vibrating electrode to examine the effect of O2 and other gases on evaporated metal films of Fe, Ni, Cr, Al, and Pb. Employing a Pt plate as a reference electrode, they found that the work function increased when the transition metals were exposed to O2 later it decreased as the chemisorbed O2 was converted to an oxide layer. With Al and Pb, however, the work function steadily decreased... 

On-board type oil deterioration pH sensor. Considering practical use as an on-board type pH sensor, it is desirable to use rigid materials for the electrodes which are thought not to be damaged due to mechanical vibrations of the engine. Therefore, oxidized stainless steel and lead electrode were selected as the pH-response electrode and the reference electrode, respectively. The signal of the newly developed sensor gradually increases as the deterioration of the oil... 

Scanning electrochemical microscopy (SECM) - Direct mode - Feedback mode - Generation/collection mode Scanning reference electrode technique (SRET) Scanning vibrating electrode technique (SVET) Scanning photoelectrochemical microscopy (SPECM) Scanning electrochemical induced desorption (SECMID)... 

The two metals act as the plates of a condenser, one of the plates being used for adsorption of the gas and the other being a reference electrode. Adsorption of gas causes a change in contact potential equal to the change in work function. Disappearance of the electrical field between the two plates may be detected either by the steady condenser method or the vibrating condenser method ... 

Electrochemical Raman, electrochemical ESR, and scanning vibrating reference electrode studies... 

Kelvin probe force microscopy (KFM) [113-116] is a well-established technique for measnring the contact potential differences (CPDs) between a reference electrode and a sample its basic operation is similar to EFM. In KFM, two conductors (sample and tip) are arranged as a parallel plate capacitor with a small spacing. In a simple model, the contact potential between the two materials is Vcpd = -(4 i - where 4>i and O2 are the work functions of the conductors, including changes due to the adsorbed layers. A periodic vibration between the two plates at a frequency co gives an alternating cnrrent (AC) with the same frequency co when the two plates have different work functions. 

Vibrating Kelvin probe measurements are relatively easy to carry out except for two troublesome problems. First, it is difficult to find a stable and inert reference electrode. Gold is usually the first choice, but 0au can vary by 0.3 V, and is susceptible, as are the work functions of other metals, to adsorbates and thermal cycling. Stainless steel and conducting oxide layers have also been used as reference electrodes with varying success. There is no sure recipe available except the experience that aged reference surfaces are more stable ( 0.02 V) than fresh and clean ones. 

Fig. 5.10 Vibrational (SFG) spectrum of CO/Pt(l 11) with CO in solution. Peak position and site assignment o = 0.0 mV, = 400 mV vs Pd/H2 reference electrode, ssp polarization [103].

D.A. Worsley, H.N. McMurray, A. Belghazi, Determination oflocalized corrosion mechanisms using a scanning vibrating reference electrode technique, Chem. Commun. (1997) 2369—2370. 

The vibrating electrode is generally also the reference electrode. 

---