Electrodes Pseudoreference

Fig. 4.9 Cyclic voltammograms of silicon anodes of different crystal orientation (1015 crrf3, boron doped, versus a Pt pseudoreference electrode in 5% HF), with the characteristic...

A lower limit of bias is given by the onset of unstable macropore formation. This is shown in Fig. 9.13, which shows the pore morphology and the corresponding formation conditions in the current density-voltage plot The current density J is held constant by the intensity of the backside illumination, so that the influence of the applied bias can be studied independently. At -0.4 V, versus a platinum wire as a pseudoreference electrode, the current density is constant over the... 

Fig. 2 Cyclic voltammogram of a Sg -I- DMF solution (2.5 mM, 293 K 1 Vs-h working electrode F -electrode pseudoreference electrode Pt-wire).

Assemble also a platinum wire as auxiliary electrode, and a Ag/AgCl wire as pseudoreference electrode, at the beginning and at the end of the series of the eight metal electrodes, respectively. 

Surface pretreatment The electrode surface was activated in ABS applying a constant potential +1.6Y (vs. Ag/AgCl pseudoreference electrode) for 2 min and +1.8Y for lmin to oxidise eventually occurring impurities. All procedures were executed in stirring solution. 

In amperometric detection, a reference electrode was usually employed. However, in one report, a platinized Au electrode was used as a pseudoreference electrode in a three-electrode system for amperometric detection. The operation principle follows that of the hydrogen reference electrode [242]. 

Fig. 7.9 Cyclic voltammograms of bithiophene polymerization (0.1 M, 50mVs 1) (a) growth and (b) post-growth in [C2mim][NTf2], (c) growth and (d) post-growth in [C4mpyr][NTf2], vs. a Ag pseudoreference electrode. Arrows indicate the peak development with successive scans [27].

The most popular pseudo-reference electrodes are Pt or Ag wires. Other pseudoreference electrodes have employed coating, for example Pt with polypyrrole [39] or Ag with AgCl [40] (but in the absence of deliberately added solution phase, ... 

It is also possible to scan a pair of reference or pseudoreference electrodes separated by a small, fixed distance of a few micrometers to measure the local potential field gradient, dvldl, and estimate the local current density from Eq. (48) (128). This is a slightly more sophisticated measurement because the anodic or cathodic character of local sites can be determined from the polarity of the current, and the intensity of the attack can be estimated from the current density flowing in solution. The difficulty with this arrangement is that the potential difference between two closely spaced reference electrodes in a conductive solution is usually less than 1 microvolt. The stability of reference electrodes is on the order of microvolts, and thus it often exceeds the magnitude of the potential difference signal. This imposes a fundamental limitation on the usefulness of this technique. 

Figure 53 Schematic illustration of the pseudoreference electrode pair used to make LEIS measurements. In this diagram, d refers to the electrode separation and h refers to the height of the probe from the working electrode surface. (From F. Zou, D. Thierry, H. S. Isaacs. J. Electrochem. Soc. 144, 1957 (1997).)...

In LEIS measurements, the working electrode is under potential control in a three-electrode cell. The pseudoreference electrode pair is then brought close to the sample surface to measure the local AC current density. A key assumption behind LEIS is that in the potential field near a working electrode surface, the AC solution current density is proportional to the local electrode impedance, and at any given measurement frequency, to, the current density in solution is... 

Here, Z(co) local is the magnitude of the local impedance, V((o)apPiied is the magnitude of the voltage between the working electrode and a distant reference electrode, and VXcoVbe is the AC voltage drop measured by the pseudoreference electrode pair. Again, it is implicitly assumed that the current density measured in solution is equal to the current density at the electrode surface. 

Pseudoreference electrode reference electrodes, and -> quasireference electrode... 

Quasireference electrode (QRE) — (-> reference electrode, pseudoreference electrode). An electrode that maintains a given, but generally not well-defined, potential during the course of a series of electrochemical experiments. It has the advantage of not contaminating the test solution by solvent or ions that a conventional reference electrode might contain and transfer. Thus in studies in aprotic solvents, like acetonitrile, a silver wire can behave as a QRE. It must be calibrated with respect to a true reference electrode or reference redox couple that is added at the end of the experiments to obtain meaningful potential values. 

Fuel cell researchers have also investigated other reference electrodes, such as a pseudo-reference electrode constructed by inserting a micro-sized carbon filament between two polymer electrolyte membranes [73], The main advantage of pseudoreference electrodes is their easy implementation, although one disadvantage is that their DC potential is unknown. However, this DC potential may not be that critical because EIS measurements mainly rely on the AC perturbation signal from which the impedance is calculated. 

Perfluorosulfonic acids may be used similarly [299]. They may be purified by distillation and treatment with H2O2 [300]. Trifluoromethanesulfonic acid has been used as solvent for CV with sodium trifluoromethanesulfonate as supporting electrolyte, glassy carbon as indicator electrode, platinum as counterelectrode and a silver wire as pseudoreference electrode. At v = 100 mV s the accessible potential window was from +0.4 to +3.0 V vs NHE (calibrated against Ru(bpy)3 ) [301]. 

Figure 5.1 Disassembled view of the spectroelectrochemical cell. (1) Tightening brass cap (threaded inside). (2) Brass ring required to tighten the cell. (3) Working electrode (brass rod with platinum soldered to the base). (4) Auxiliary electrode platinum wire with the tip made flush to the teflon base of the cell. (5) Pseudoreference electrode silver wire, also made flush to the teflon. (6,7) Luer-lock-type injection ports. (8) Cell body, top part aluminium, lower part teflon. (All three electrodes and both filling ports are press fitted into the cell body, so that they can be replaced if needed.) (9) Teflon spacer, determines the pathlength of the cell and masks the reference and counter electrodes from the incident beam. (10) Calcium fluoride window (Wilmad, standard 38.5 x 19.5 x 4mm). (11) Rubber gasket. (12) Hollow brass cell body with threaded inlet and outlet ports (Swagelock) for connection to circulating bath. (13) Two-mirror reflectance accessory (Thermo-SpectraTech FT-30). (14,15) Mirrors.

A laminated platinum-mesh working electrode positioned in an EPR fiat cell combined with a Ag pseudoreference electrode and a Pt counter electrode was used by Dunsch and coworkers for the in-situ study of C120O. The same group also performed simultaneous variable temperature EPR/UV-Vis-NIR experiments on Wurster s reagent and thianthrene. Similar cells using laminated ITO and gold working electrodes have also been reported. ... 

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