Nickel anodes

Datha, M. and Landolt, D., Stoichiometry of Anodic Nickel Dissolution in NaCl and NaC103 Under Active and Transpassive Conditions , Corros. Sci., 13, 187 (1973)... 

A—Cadmium Cadmium anode Nickel, mercury, and silver Secondary Nickel-cadmium, mercury-cadmium, and silver-cadmium... 

Figure 11-15 shows the corrosion rate observed for a metallic nickel electrode in aerated aqueous sulfate solutions as a function of pH. In addic solutions, nickel corrodes in the active state at a rate which is controlled by the diffusion of hydrated oi en molecules (oxidants). In solutions more basic than pH 6, however, nickel spontaneously passivates by hydrated oiQ n molecules and corrosion is negligible. As shown in the inserted sub-figures in Fig. 11-15, the maximum current of anodic nickel dissolution in the active state is greater in the range of addic pH however, the Tnaximnm current of anodic nickel dissolution is smaller in the range of basic pH than the current of cathodic reduction of os en molecules (dashed curve) which is controlled by the diffusion of hydrated oiQ gen molecules. Consequently, metallic nickel remains in the active state in addic solutions but is spontaneously passivated by hydrated ojQ n molecules in basic solutions. It... 

The structure of complex behavior in anodic nickel dissolution was analyzed and... 

The Edison cell uses an iron anode, nickel oxide eathode, and KOH electrolyte. This cell is extremely rugged and is still used in certain industrial apphcations, but it was never able to displace the lead-acid cell as Edison had hoped.. 

Fig. 13.22. The monolithic SOFC concept of Argonne National Laboratory. Anode nickel-yttria-stabilized zirconia. Cathode strontium-doped lanthanum manganite. Interconnect doped lanthanum chromite, a, Interconnection b, electron-ion path c, anode d, electrolyte e, cathode. (Reprinted from K. Kordesch,...

BDD anode, nickel cathode, Q = 1.0 F per mol37 Determined from crude product by GC using an internal standard bCurrent efficiency... 

Table 5 Electrolysis conditions BDD anode, nickel cathode, 30 mL HFIP, 50 °C, P A = 1 10...

World nickel metal production in 2002 was 678000 tons [39]. Hydrometallurgy has typically been applied to the treatment of nickel-copper mattes, anode nickel, and reduced laterite ore. The sulfide concentrates are usually oxidized by roasting and then smelted to copper-iron-nickel sulfide matte (75-80% Cu-Ni), which is refined or used directly to make M onel metal. Cathode nickel can be produced from a variety of electrolytes, including chloride, sulfate, or a mixed chloride-sulfate. The former two are acid systems used in leaching and electrowinning. Mixed chloride-sulfate electrolytes are used for electrorefining the nickel sulfide matte from the traditional matte-smelting operations. 

The intensity at the focus provided by each of the instruments can be compared with the intensity of a laboratory rotating anode (nickel filtered, Elliott GX6) beam behind a 0.3 mm diameter collimator of 9x 108 photons s-1 mm-2 (Harmsen, Leberman and Schultz 1976). 

It was proposed that the rate-controlling step in processes of this kind was the abstraction of the H at the a-carbon of the alcohol by the anodic nickel oxide film which is chemically closely related to the so-called nickel peroxide reagent (not really a peroxide ) The reaction mechanism suggested can be represented as follows ... 

The two types of high temperature fuel cell are quite different from each other (Table 6). The molten carbonate fuel cell, which operates at 650°C, has a metal anode (nickel), a conducting oxide cathode (e.g. lithiated NiO) and a mixed Li2C03/K2C03 fused salt electrolyte. Sulphur attack of the anode, to form liquid nickel sulphide, is a severe problem and it is necessary to remove H2S from the fuel gas to <1 ppm or better. However, CO is not a poison. Other materials science problems include anode sintering and degradation, corrosion of cell components and evaporation of the electrolyte. Work continues on this fuel cell in U.S.A. and there is some optimism that the problem will be solved within 10 years. 

The electrochemical vapor deposition (EVD) process has been successfully developed as fabricating a dense electrolyte film on porous cathodes and fixing anode nickel particles on the electrolyte plate with YSZ. This provides a nearly ideal microstmcture for electrolyte/electrode interfaces. 

The German company Siemens later modified these electrodes with skeleton metal catalysts. Small amounts of titanium were added to the anodic nickel catalysts, and nickel, bismuth, and titanium were added to the cathodic silver catalysts. Fuel cells with such electrodes and a matrix electrolyte operated at 95°C and a current density of 400 mA/cm had a working voltage of 0.8 to 0.9 V. 

The IR spectrum of NiCO isolated in solid argon gave assignments to Vi, V3 and V5 modes, with isotopic shifts.The IR spectrum of CO adsorbed on Nin clusters shows the presence of 4 (vibrationally-coupled) CO molecules per cluster. FTIR spectra (vCO) were used to probe the effects of co-adsorption of on-top CO on bridge CO on a Ni(lll) surface.The FTIR spectrum of CO on an anodic nickel oxide surface had a band at 2112 cm assigned to CO adsorbed to Ni(II) or Ni(0) sites perturbed by oxidation of neighbouring nickel atoms. The geometry of CO or NO coordination on NiO(lll) thin films was deduced from the vCO and vNO values. 

Oxidation-reduction intolerance (anode) Nickel oxidizes rapidly, and expands by 69 vol% under oxidation. Because of the large volume change during reducdon/oxidadon, the structure of the anode and its mechanical strength are severely affected and the Ni-YSZ anode heavily degrades during redox cycles. The anode may break apart when exposed to air, which can occur during start-up and shutdown of the fuel cell system. With a Ni-YSZ supported cell the electrolyte will crack in the first redox cycle. An anode that does not need protecdon from air would simplify the system and lower costs. 

For the anode, nickel is still the best choice for operation in the intermediate-temperature region. Most frequently observed effects on nickel anodes are sulfur poisoning. It is well known that degradation caused by hydrogen sulfide becomes more severe with decreasing temperature. 

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