Open-circuit electrode potential

It should also be recalled that, for many electrodes in various solutions, the open circuit electrode potential, i.e. the electrode potential in the absence of current flow, is not the thermodynamic equilibrium but rather a mixed potential, discussed in Section 5.8.4. 

This value is maximized when EF reaches the flatband potential. Thus, a plot of incident light intensity versus open-circuit electrode potential is expected to saturate at the flatband potential, thereby allowing identification of this potential. A typical experiment of this sort is shown in Figure 28.3b for an n-CdSe electrode immersed in a ferri/ferrocyanide electrolyte. 

Fig. 5.78. SR spectra of a glassy carbon electrode activated electrochemically before (—) and after decoration with silver in contact with an aqueous solution of 0.1 M K2SO4, open circuit electrode potential, Laser = 514.5 nm, Pq = 100 mW, resolution 2 cm" (based on data in [354])...

A. Response of the Open-Circuit Electrode Potential to a Change in the Interfacial Temperature in the Presence of a Perfectly Reversible Redox Couple Attached to the Electrode Surface 121 The Relaxation of the ILIT Response When the Rate of Electron Transfer Is Not Infinitely Fast 126 When Is the ILIT Response Purely Thermal (i.e., Devoid of Kinetic Information) 126 The Shape of the Ideal ILIT Perturbation 130 Nonidealities of the Shape of the ILIT Perturbation and Response—Extracting the Relaxation Rate Constant, 134... 

A. Response of the Open-Circuit Electrode Potential to a Change in the Interfadal Temperature in the Presence of a Perfectly Reversible Redox Couple Attached to the Electrode Surface... 

In a recent communication, Fenner, Van Dyke, and Martin report a variant of the chronopotentiometric current pulse technique, which involves examining the time variation of the open-circuit electrode potential. The open-circuit potential recorded after applying a current pulse varied in a linear manner with The charge transport diffusion coefficient is evaluated by comparing simulated and experimental oc transients. Martin and coworkers show that the concentration of diffusing species at any distance x in the film at any time t after terminating the current pulse is given by... 

The open-circuit electrode potential can be of various nature. If several conju-... 

Potentiometry, which measures the open-circuit equilibrium potential of an indicator electrode, for which the substance being examined is potential determining... 

Alternatively, a potentiometer connected across the open circuit is found to register a potential difference that renders the Cu electrode positive relative to the Zn electrode the magnitude of the open—circuit electrochemical potential difference, which later will be shown to be identical with the electromotive force (emf), symbolized by fS, is approximately 1.1 volts. 

The constant term depends on the environmental conditions such as temperature, pH, concentration of oxygen and the reference electrode offset. But the differential method without the term has advantages on them, in case that the same reference electrodes are used in the short-time measurement. This formulation easily eliminates the effect of open circuit corrosion potential and reference electrode offset. If the potential or current density are constant in two boundary conditions, the differential boundary conditions are zero according to Eqn. (12) or Eqn. (13). 

The both numerical and experimental potential distributions are shown in Figure 7 and they show good agreement. It is noted that the good agreement can be achieved even if the open circuit corrosion potential is unknown, polarization curve is non-linear and unknown and there are the offsets of reference electrodes. 

Examples of metals that are passive under Definition 1, on the other hand, include chromium, nickel, molybdenum, titanium, zirconium, the stainless steels, 70%Ni-30% Cu alloys (Monel), and several other metals and alloys. Also included are metals that become passive in passivator solutions, such as iron in dissolved chromates. Metals and alloys in this category show a marked tendency to polarize anodicaUy. Pronounced anodic polarization reduces observed reaction rates, so that metals passive under Definition 1 usually conform as well to Definition 2 based on low corrosion rates. The corrosion potentials of metals passive by Definition 1 approach the open-circuit cathode potentials (e.g., the oxygen electrode) hence, as components of galvanic cells, they exhibit potentials near those of the noble metals. 

The gold working electrode has two roles in this experiment first, with its potential controlled at —0.550 mV, it is the cathode at which the MV++ is reduced. After transferring an aliquot of charge, which is transferred to the protein and the mediator, the potentiostat is turned off, and the cell is held at open circuit in order for the contents of the cell and the gold electrode to equilibrate at open circuit. The potential of the electrode and the spectrum... 

In electrochemical noise (EN) measurements fluctuations in potential or current are measured as a function of time. The measurements can be done (see Chapter 7) either without or with an externally applied signal. In the first case one monitors the open circuit corrosion potential of the test metal versus a suitable reference electrode or versus a second electrode of the seune material exposed under identical conditions. The advantage of this technique for use in MIC research is that there is no external signal to disturb the biological community on the metal surface. Alternatively, one can measure fluctuations in potential (E) at an applied current (I), or the reverse, fluctuations in I at an applied E. It has also been suggested that one could couple the metal of interest to a platinum electrode and measure the noise... 

When chemical species come into equilibrium with an electrode in an open circuit, the potential between the electrode and a reference electrode is related to the potential difference of the half reaction occurring at the electrode. If no... 

Park, J. H. Zhou, H. Percival, S. J. Zhang, B. Fan, F.-R. F Bard, A. J. 2013. Open circuit (mixed) potential changes upon contact between different inert electrodes-size and kinetic effects. Anal. Chem. 

To predict the local polarisation in a full-scale cell or stack at any point, its dependence on composition, pressure, and temperature of the gas flowing in the gas channel contacting the electrode must be known. In a large cell, these bulk gas properties vary from one point to the next. Electrode polarisation or overpotential - the difference between the local potential of the electrode under load and the potential at open circuit (equilibrium potential) - is also a local quantity because it depends not only on the bulk gas composition but also on the current density. In a large cell the current is usually distributed nonuniformly, as discussed in Sections 11.2-11.5. Similar to Eq. 7, one can express the local cell voltage under load, i.e., when current is passed, as the thermodynamic cell potential minus three loss terms the ohmic loss, the cathode polarisation, and the anode polarisation ... 

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