Reference electrode desorption

Figure 5.25. Redhead plot for oxygen desorption from a Pt film deposited on YSZ for various catalyst film potentials vs Au reference electrode. The slope of each line is equal to Ed/R.7 Reprinted with permission from Academic Press.

The reasons are analyzed in detail in Chapter 5. The equation is valid as long as the effective double layer is present at the metal/gas interfaces of the working and reference electrodes. Deviations are basically observed when ion backspillover is not faster than ion desorption or reaction (see also section 11.3). 

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)... 

Figure 4.22 Simultaneous idealized representation of ETSM processes. Curve a (solid line) represents the current flow in the cell for a redox cycle, while curve b (dotted line) represents the concurrent frequency shift associated with the adsorption (fwward arrow) and desorption (reverse arrow) of mass at the electrode surface during the redox electrode reaction. The reference electrode is a saturated calomel electrode (SCE).

For polarized interfaces (mercury) the point of zero charge is not defined by the composition of the solution rather, it is a certain applied potential with respect to a reference electrode. It is the potential of the electrocapillary maximum, also called the potential of zero charge, see [1.5.6.17]. In this case, the two charging processes are supply and withdrawal of electrons, the einalogues of desorption and adsorption of protons on oxides. 

A typical electrochemical NOx sensor design involves the use of two electrodes on an oxygen-ion conducting ceramic, such as yttria-stabilized zirconia (YSZ), as shown in Fig. la. Both chemical and electrochemical reactivity at each electrode is critical to sensor performance [8, 18-20]. We have obtained optimal results with a Pt electrode covered with Pt-containing zeolite Y (PtY) as the reference electrode and WO3 as the sensing electrode [17, 21, 22]. These electrodes were identified by temperature programmed desorption of NO from NOx/02-exposed PtY and WO3, and the ability of PtY and WO3 to equilibrate a mixture of NO and O2. Significant reactivity differences were found between the PtY and WO3, with the latter... 

For nonvolatile or thermally labile samples, a solution of the substance to be examined is applied to the emitter electrode by means of a microsyringe outside the ion source. After evaporation of the solvent, the emitter is put into the ion source and the ionizing voltage is applied. By this means, thermally labile substances, such as peptides, sugars, nucleosides, and so on, can be examined easily and provide excellent molecular mass information. Although still FI, this last ionization is referred to specifically as field desorption (FD). A comparison of FI and FD spectra of D-glucose is shown in Figure 5.6. 

Figure 5.21. Experimental setup (inset) showing the location of the working (WE), counter (CE) and reference (RE) electrodes and of the heating element (HE) thermal desorption spectra after gaseous oxygen dosing at 673 K and an 02 pressure of 4x1 O 6 Torr on Pt deposited on YSZ for various exposure times. Oxygen exposure is expressed in kilo-langmuirs (1 kL=l0 3 Torrs). Desorption was performed with linear heating rate, ()=1 K/s.4 S Reprinted with permission from Academic Press.

Figure 1 Schematic of the experimental UHV/electrochemical transfer system used for studies on modified platinum single-crystal surfaces. (From Ref. 26.) The UHV system has facilities for X-ray photoelectron spectroscopy (XPS), low-energy ion scattering spectroscopy (LEISS), low-energy electron diffraction (FEED), and temperature-programmed desorption (TPS). The electrochemical chamber allows the electrochemical cell, 0 with integral counter, reference, and secondary working electrode, to be brought to the surface allowing contact of the electrolyte with the transferred surface.

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