Normal Standard Hydrogen Electrode

Normal/Standard Hydrogen Electrode (NHE/SHE) it is the standard reference electrode, all standard potentials are referred to NHE, its potential is by definition 0.000 V. Oxidation refers to the process in which a chemical species loses one or more electrons ... 

QCMB RAM SBR SEI SEM SERS SFL SHE SLI SNIFTIRS quartz crystal microbalance rechargeable alkaline manganese dioxide-zinc styrene-butadiene rubber solid electrolyte interphase scanning electron microscopy surface enhanced Raman spectroscopy sulfolane-based electrolyte standard hydrogen electrode starter-light-ignition subtractively normalized interfacial Fourier transform infrared... 

The relative electrode potential nhe referred to the normal (or standard) hydrogen electrode (NHE) is used in general as a conventional scale of the electrode potential in electrochemistry. Since the electrode potential of the normal hydrogen electrode is 4.5 or 4.44 V, we obtain the relationship between the relative electrode potentiEd, Ema, and the absolute electrode potential, E, as shown in Eqn. 4-36 ... 

Normal hydrogen electrode (see Standard hydrogen electrode)... 

The hydrogen electrode. The hydrogen electrode is discussed first because it is the primary reference electrode used to define an internationally accepted scale of standard potentials in aqueous solution. By convention, the potential of an electrode half-reaction that is measured with respect to the normal hydrogen electrode (NHE also written as SHE, standard hydrogen electrode) is defined as the electrode potential of the half reaction. This convention amounts to an arbitrary assignment for the standard potential of the hydrogen electrode as zero at all temperatures. Thus, there is in effect a separate scale of electrode potentials at each temperature level. 

When properly engineered and with [H30(aq)] at unity activity and Pm at unit fugacity, this electrode system is the thermodynamic reference standard for measurements of electrochemical potentials, and is referred to as the normal hydrogen electrode (NHE), which is alternatively called standard hydrogen electrode (SHE) ... 

As indicated previously, it is desirable to consider the individual electrode reactions independently. One might suppose that this could be achieved by characterizing the individual electrodes as described in Section 3.1.3. However, for reasons of sound thermodynamics, another method has been established. It was decided to relate all electrode reactions to one common reference electrode. Electrochemists have chosen the H+/H2 reaction under standard conditions (ct 1+ = 1M p 12 = 1 bar) as such a general reference electrode. It is termed the normal hydrogen electrode or the standard hydrogen electrode (SHE). Thus, whenever E and E° values are presented for individual electrode reactions (half cells), it is understood that these values pertain to a complete cell in which the SHE constitutes the second electrode. 

Fig. 16.9 CB and VB energy levels of several semiconductors. (The semiconductors are in contact with aqueous electrolyte at pH 1. The energy scale is indicated in electron volts using either the normal hydrogen electrode (NHE) or vacuum level as reference. On the right the standard potentials of several redox couples are presented against the standard hydrogen electrode potential.) [Reprinted by permission from Macmillan Publishers Ltd [Nature] (Gratzel 2001), copyright (2001)]...

Standard hydrogen electrode — The standard -> hydrogen electrode (SHE) is the primary standard in electrochemistry [i-v]. It is also called normal hydrogen electrode (NHE), however, this usage is no longer recommended. 

There are two other common versions of this half-cell the normal and tenth normal csAo-mel electrodes, in which the KCl concentration is either 1.0 or 0.1 N. The saturated electrode is the easiest to prepare and the most convenient to use but has the largest temperature coefficient. The half-cell potential for each of the calomel electrodes has a different value relative to the standard hydrogen electrode these emf valnes are given in Table 1. Calomel electrodes can be easily prepared in the laboratory and are also available commercially. Two typical calomel electrode designs are shown in Fig. 7. 

The standard hydrogen electrode is sometimes called the normal hydrogen electrode (NHE). 

Normal error curve A plot of a Gaussian distribution of the frequency of results from random errors in a measurement. Normal hydrogen electrode (NHE) Synonymous with standard hydrogen electrode. 

In the above equation, if a = 1, then E = eP. The standard potential of an electrode eP is the potential of an electrode in contact with a solution of its ions of unit activity. The standard potentials are always expressed against the standard hydrogen electrode (SHE), the potential of which is zero by definition. The standard potentials are a function of temperature they are usually tabulated for 25° C. Standard electrode potential is also called normal electrode potential. 

To create a scale of electrode potentials based on eq. 1 A. 12, we need to know the contact potential difference between the solution phase of a suitable reference electrode system and the electrode itself. The most accurate measurements of this type have been made by using the standard hydrogen electrode as the reference electrode and mercury, the work function of which is known to good accuracy (although it is not normally used in the SHE), as the reference metal. Equation 1A.12 then gives... 

Each electrochemical couple exhibits a characteristic electrochemical potential and a characteristic Acell voltage C, defined above, depends on the couples combined in a cell and on their concentrations. In order to quantify the properties of electrochemical couples reference electrodes are used. The reference electrode which is primarily used is the standard hydrogen electrode (SHE), or normal hydrogen electrode (NHE). In this case it is an inert Pt electrode around which hydrogen is flushed (see Fig. 3.4). The reaction involved is given by... 

Other abbreviations may also be used in tables, such as SHE for the standard hydrogen electrode or SCE for the saturated calomel electrode. The abbreviation NHE has been widely used for the normal hydrogen electrode , which is by definition identical to the SHE. It should nevertheless be noted that NHE customarily refers to a standard state pressure of 1 atm, whereas SHE always refers to a standard state pressure of 0.1 MPa (1 bar) in this review. 

Within the normal range of electrolyte concentrations (4.5-5.6 M H2SO4), the equilibrium potential, E, of the negative electrode is —0.330 to —0.345 V with respect to a standard hydrogen electrode (SHE). Deviations from this value during charge and discharge (i.e., the overpotential, tj) as a result of kinetic hindrances and resistive losses can be conveniently related to the current density, i, by the Tafel equation... 

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