High EMF Research Articles

Electrochromic Cells Using Some Transition Metal Complexes

Electrochromic cells using aqueous solutions of tris (2, 2'-bipyridine) cobalt(II) complex salts are described. Colored film formed on the cathode was ascribed to Co(I) complex salts which were formed by the cathodic reduction of Co(II) complex ions. The persistence of the colored film was ca. 30 min. This limited persistence was interpreted in terms of the proportionation reaction between the colored species and anodically generated Co(III). Co(III) ion is also assumed to scavenge the diffused Co(I). This reaction is discussed in terms of the stability of the electrochromic system. Emf (electromotive force) built in the persistent state showed 1.1 V. This high emf was attributed to the deposited film of the Co(I) salt, not to the polarization of the ionic species in the solution.

Some Considerations in Establishing Thermodynamic Activities from High Temperature EMF Measurements*

Some Considerations in Establishing Thermodynamic Activities from High Temperature EMF Measurements*

Etude du couple CuSO4-Li en vue de la realisation d'un accumulateur

The Li-CuSO4 couple has a high density, 1060 Wh/kg, and a high emf, 3.41 V. Copper sulphate is not soluble in the electrolyte and though there are SO42− ions in solution it does not form complexes. Lithium sulphate is slightly soluble: for this reason when the negative electrode is charged there is no formation of dendrites. The organic solvent used is dimethyl sulphate: the best composition of the electrolyte is 0.25 mol/l of tetrabutylammonium sulphate with 1.25 mol/l of tetrabutylammonium perchlorate. The perchlorate ion prevents passivation of the lithium electrode. The Li2SO4/Li and CuSO4/Cu systems are reversible. Lithium is not thermodynamically stable in contact with dimethyl sulphate: it reacts slowly and ethane is evolved. We have not found any material that could be added to lithium to improve the specific area of the electrode.

Thermodynamics of Hydrocarbon Fuel Cells

Recently, there has been a great increase in activity in the field of hydrocarbon fuel cells. A rather neglected area has been that of the thermodynamics of the reactions in the anode compartment. The conditions under which a fuel cell must be operated in order to prevent carbon deposition have been calculated for the system at 500°K under two important sets of conditions. Two literature methods for the calculation of the complex gas phase equilibria were evaluated, and an improved method extending one of these methods is presented. The calculations show that unexpectedly high and constant emf values are possible. Appreciable amounts (ca. 1%) of hydrogen were found to be present at equilibrium over a wide range of fuel compositions at 500°K. The levels of CO partial pressures at equilibrium were found to be about 10−5 atm.