Electrode, working reference

Under potentiostatic conditions, the electrode potential is set on the plateau of the A —> B transition. During the electrolysis, the current will decrease with the concentration of A and reach zero (curve d). The process is quite selective, as the other electrode process cannot take place. Note that this electro synthetic procedure requires the use of a potentiostat with three electrodes (working, reference, and auxiliary). 

The electrochemical cell in voltammetry has three electrodes working, reference and auxiliary (counter) (Figure 5.6). The sample is placed in this voltammetric cell, the voltage or voltage ramp applied as required and the resulting current measured. 

A typical arrangement for a voltammetric electrochemical cell is shown in Figure 11.28. Besides the working, reference, and auxiliary electrodes, the cell also includes a N2 purge line for removing dissolved O2 and an optional stir bar. Electrochemical cells are available in a variety of sizes, allowing for the analysis of solution volumes ranging from more than 100 mL to as small as 50 )+L. 

The question of what happens when an electrical signal is appHed to an electrochemical ceU needs to be answered with respect to the three components of the ceU the working electrode, the reference electrode, and the sample itself. 

Figure 4a. Electrochemical cells for microwave conductivity measurements. Cell above microwave conduit (1) electrochemical cell (plastic tube, placed on working electrode material), (2) counter-electrode, (3) reference electrode, (4) electrolyte, (5) space charge layer, (6) diffusion layer, (7) contact to working electrode, (8) waveguide.

Fig. 16. Small-scalo laboratory cell for preparative electrolysis. A, Pt gauze working electrode. B, Pt sheet secondary electrode. C, Reference electrode. D, Luggin capillary on a syringe barrel so that the position of the tip of the Luggin probe relative to the working electrode is readily adjustable. E, Glass sinter to separate anode and cathode compartments. F, Gas inlet to allow stirring with inert gas or the continuous introduction of reactant. G, Three-way tap where a boundary between the reference electrode and the working solutions may be formed.

Reference electrodes for non-aqueous solvents are always troublesome because the necessary salt bridge may add considerable errors by undefined junction potentials. Leakage of components of the reference compartment, water in particular, into the working electrode compartment is a further problem. Whenever electrochemical cells of very small dimensions have to be designed, the construction of a suitable reference electrode system may be very difficult. Thus, an ideal reference electrode would be a simple wire introduced into the test cell. The usefulness of redox modified electrodes as reference electrodes in this respect has been studied in some detail... 

CE-COUNTER ELECTRODE RE-REFERENCE ELECTRODE WE-WORKING ELECTRODE... 

An important step in measurements of electrode potentials is that of selecting a suitable reference electrode (RE). Reference electrodes with electrolytes of the same nature and same (or similar) composition as that at the working electrode are used... 

Figure 8.2 In situ SXS electrochemical cell WE, working electrode CE, counter-electrode RE, reference electrode. On the left is shown the transition from (1 x 1) to (hex) for a Au(lOO) surface and on the right the characteristic adsorbate structures of CO on Pt(lll) commonly observed by SXS.

Figure 12.2 The electrochemical cell has a 25 p-m Teflon spacer sandwiched between the electrode and a window (Cap2 or Mgp2) to provide an electrolyte layer of known and controlled thickness. Working, reference, and auxiliary electrodes are indicated. Construction materials are glass and Teflon.

Figure 15.2 Schematic representation of different electrochemical cell types used in studies of electrocatalytic reactions (a) proton exchange membrane single cell, comprising a membrane electrode assembly (b) electrochemical cell with a gas diffusion electrode (c) electrochemical cell with a thin-layer working electrode (d) electrochemical cell with a model nonporous electrode. CE, counter-electrode RE, reference electrode WE, working electrode.

Fig. 5.35 SNIFTIRS spectrum from a polished Pt electrode in 0.5 m LiC104 in propylene carbonate. Reference potential 2.00 V versus Li/Li+ electrode working potential 3.20 V versus Li/Li+ electrode. According to P. Novak et al.

Figure 2.39 (a) Schematic representation of the experimental arrangement for attenuated total reflection of infrared radiation in an electrochemical cell, (b) Schematic representation of the ATR cell design commonly employed in in situ 1R ATR experiments. SS = stainless steel cell body, usually coated with teflon P — Ge or Si prism WE = working electrode, evaporated or sputtered onto prism CE = platinum counter electrode RE = reference electrode T = teflon or viton O ring seals E = electrolyte. 

Figure 2.81 (a) Schematic of the system for in situ X-ray reflectivity measurements. Syn = synchrotron source M = monochromator S = slit /0, /R = incident and reflected X-rays beams, respectively 9 = angle of incidence W = teflon windows WE = working electrode RE = reference electrode CF = counter electrode D = scintillation detector, (h) Cyclic voltammogram of Cu-on-Si electrode in borate buffer solution (pH 8.4), scan rate = lOmVs-1. From Melendres... 

The potential of the working electrode versus the reference electrode is referred to as the potential of the working electrode (i.e. the detection potential). 

Substance or Substance Class Detection Potential Working Electrode Material Reference Number... 

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