Impedance Analysis of the Hydrogen Oxidation Reaction in Molten Li/K Carbonate at Nickel Electrodes

Corrosion of Nickel in Molten Carbonate

“…These ions may be formed according to the following electrochemical reaction, given in the defect-chemical-notation of KrSger and Vink 23 The formation of trivalent nickel ions may be accompanied by the incorporation of Li § in the nickel oxide lattice, which can be described by the following chemical reaction V~}l + 2Li + + 02-~ 2Li~ + O~ [16] If all nickel vacancies are filled with lithium ions, the fraction of trivalent nickel ions is equal to the fraction of lithium ions. The Ni 3+ fraction can be estimated by ameas 2ro2-~ 2rNi2+ araeas --a0 XNa~ = X~ = 2r~3+ + 2rLi+ -4rN12+ -0.16 [17] Based on this equation, the Ni 3. fraction estimated from averaging the results of three samples after polarization for 10 rain in the potential range where the trivalent nickel is formed, was 0.009 • 0.004 at a nickel basis [Nia § 2+ + Ni3*)], which is of the same order of magnitude as when lithium ions are not incorporated in the lattice.…”

“…Indeed, it was shown that the electrochemical reduction of silver ion-exchanged zeolites leads to the formation of silver clusters and particles within the zeolite framework as well as on the surface of the solid. [16][17][18][19] In this paper we describe the use of electrogenerated silver particles on a Y zeolite-encapsulated iron-SALEN complex to facilitate electron transfer reactions and to enhance the electroactivity of such materials.…”

Electrode Behavior of Hydrogen Reduction in LiCl-KCl Melt. Voltammetric Analysis

“…Since ⌬G ϭ ϪnFE and the activity can be expressed as the product of activity coefficient and concentration of each species, the electrode potential E is [4] where E o is the standard potential of the electrode and ␥ H2 , ␥ H Ϫ and [H 2 ], [H Ϫ ] represent activity coefficients and concentrations at the electrode surface for each species, respectively. If the activity coefficients of both species are assumed to be constant, then the electrode potential can be written as [5] where [6] Initially, the bulk and surface concentrations of H 2 and H Ϫ are equal and n ϭ 2; hence, the electrode rest potential E rest is given by [7] where C* H2 and C* H Ϫ are the bulk concentrations of H 2 and H Ϫ in the electrolyte.…”

“…Hydrogen reduction in molten alkali halide is an important process for the development of thermally regenerative fuel cells using hydrogen and lithium. 1,2 Hydrogen oxidation in molten carbonate has been studied by several authors [2][3][4][5][6][7] in order to develop a molten carbonate fuel cell (MCFC). In these cases, nickel and palladium electrodes showed high activity for hydrogen oxidation compared to other electrode materials.…”

Wetting of Ni and NiO by Alternative Molten Carbonate Fuel Cell Electrolytes. II. Influence of the Electrode Overpotential

“…It should be emphasized that in the MCFC devices, Ni is used not only as a component of the anodic material but is alloyed by Cr and/or Al. According to Weewer et al, [13][14][15] these additives drastically decrease the CA values at the anodes. Therefore, these values should shift toward those determined by us for NiO cathodes, since the d a /d c ratio may be even more close to 1 than in case of pure Ni anodes.…”