Nickel standard electrode potential

The review of Martynova (18) covers solubilities of a variety of salts and oxides up to 10 kbar and 700 C and also available steam-water distribution coefficients. That of Lietzke (19) reviews measurements of standard electrode potentials and ionic activity coefficients using Harned cells up to 175-200 C. The review of Mesmer, Sweeton, Hitch and Baes (20) covers a range of protolytic dissociation reactions up to 300°C at SVP. Apart from the work on Fe304 solubility by Sweeton and Baes (23), the only references to hydrolysis and complexing reactions by transition metals above 100 C were to aluminium hydrolysis (20) and nickel hydrolysis (24) both to 150 C. Nikolaeva (24) was one of several at the conference who discussed the problems arising when hydrolysis and complexing occur simultaneously. There appear to be no experimental studies of solution phase redox equilibria above 100°C. 

The standard electrode potential for the reduction of Ni- to Ni is — 0.25V. Would the potential of a nickel electrode immersed in a 1.00 M NaOH solution saturated with Ni(OH)2 be more negative than -/Ni or less Explain. 

Attempts to measure the standard electrode potential of nickel using the similar... 

The pressure to stop the Ni corrosion cell is much less than the pressure to stop the iron corrosion ceU. Iron is more thermodynamically active with standard potential of -0.44 V vs. SHE when compared with nickel with standard electrode potential ofe° = -0.250V vs. SHE. 

Electrochemical poisoning reactions occur when the anodic potential reach electrode potentials for nickel sulfides formation the standard electrode potential for the half-reaction forming NiS and Ni3S2 are respectively —0.756 V and -0.829 V [13, 18], At open circuit voltage conditions, the anodic potential is more negative than electrode potentials necessary for either NiS or Ni3S2 formation. 

We can confirm this by calculating the standard electrode potential for manganese acting as the anode (oxidation) and nickel acting as the cathode (reduction). 

Since electrode potentials are quoted on the hydrogen scale, it might be expected that only metals with positive standard electrode potentials could be deposited from acid solutions, and that hydrogen would be discharged in preference to other cations, such as lead (E = -0.126 V) or nickel (E =-0.25 V). The failure of this prediction is due to the high activation overpotential (q.v.) of hydrogen on many metals, values obtained at a current density of 1 mA cm varying from 0.01 V on a platinised platinum cathode to as much as 0.67 V on lead and 1.04 V on mercury. 

De Souza et al. (1997) used spectroscopic ellipsometry to study the oxidation of nickel in 1 M NaOH. Bare nickel electrodes were prepared by a series of mechanical polishing followed by etching in dilute HCl. The electrode was then transferred to the spectroelectrochemical cell and was cathodicaUy polarized at 1.0 V vs. Hg/HgO for 5 minutes. The electrode potential was then swept to 0.9 V. Ellipsometry data were recorded at several potentials during the first anodic and cathodic sweep. Figure 27.30 shows a voltammogram for Ni in l.OM NaOH. The potentials at which data were recorded are shown. Optical data were obtained for various standard materials, such as NiO, a -Ni(OH)2, p-Ni(OH)2, p-NiOOH, and y-NiOOH. 

The electrochemical series corresponds only to the standard condition, i.e., for unit activity of the ions, since a change to another ionic concentration can alter the order of the electrode potentials of the elements very markedly. The case of nickel plating mentioned earlier may be taken as typically illustrative of the many practical examples of the effects and the consequences of nonstandard conditions. It must also be mentioned in the context of the examples of displacement reactions provided earlier that the concentrations and the electrode potentials frequently vary during a displacement reaction. 

Calculate the standard cell potential of a cell constructed with nickel (Ni) and copper (Cu) electrodes. 

Under standard conditions and in the absence of kinetic hindrance, the electrode potential (versus a hydrogen electrode) determines the potential at which the corresponding metal will be deposited out of an aqueous solution. Therefore, metals that have a more negative electrode potential than the hydrogen electrode cannot be deposited from aqueous electrolytes. Kinetic barriers often disfavor the production of hydrogen over metal deposition. Thus, technically important metals, such as tin, nickel, and zinc can be electrolytically deposited out of aqueous solutions without any problems, even though their electrode potentials are lower than that of the hydrogen electrode. 

A FIGURE 20.26 illustrates an electrolytic cell for electroplating nickel onto a piece of steel. The anode is a strip of nickel metal, and the cathode is the steel. The electrodes are immersed in a solution of NiS04(external voltage is applied, reduction occurs at the cathode. The standard reduction potential of Ni (E°ei 0.28 V) is less negative than that of H2O (E°ed = —0.83 V), so Ni is preferentially reduced, depositing a layer of nickel metal on the steel cathode. 

Use electrode potentials to answer the foUowing questions, (a) Is the oxidation of nickel by iron(III) ion a spontaneous reaction under standard conditions ... 

FE An electrochemical cell is composed of pure O nickel and pure iron electrodes immersed in solutions of their divalent ions. If the concentrations of Ni and Fe ions are 0.002 M and 0.40 M, respectively, what voltage is generated at 25°C (The respective standard reduction potentials for Ni and Fe are -0.250 V and -0.440 V.)... 

Although the nickel-containing systems have been extensively studied also by electrochemical methods [1] due to their practical importance, for example, in electrochemical power sources (Ni—Fe, Ni—Cd, Fi—NiF2 batteries), in corrosion-resistant alloys (tableware, coins, industrial instruments) as well as due to their interesting (magnetic, spectral, catalytic) properties most of the standard potentials of electrode... 

The midpoint reduction potentials of the various EPR-detectable nickel species in hydrogenase are all less than 0 mV versus the standard hydrogen electrode (Table II). This is in contrast to synthetic inorganic complexes with amino acids 44), in which the oxidation of Ni(II) to Ni(III) occurs at much higher potentials (0.8-1.2 mV) and is accompanied by reorganization of the complex 45). This requires some explanation in view of the interpretation of the Ni-A EPR signal as Ni(III)(7). 

An attempt by these authors to measure the standard potential of the nickel electrode with the similar cell ... 

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