High Pressure Effects on the EMF of Seawater Battery Electrodes in Chloride Electrolyte

Abstract

Reference electrodes, suitable for use at high pressures in chloride or hydrogen containing solutions, were applied to the study of various buffer equilibria at pressures from 0 to 2.5 kbar. Partial molal volumes of reaction obtained are compared and interpreted in terms of their effects on the solvent structure. Results obtained with anodes of magnesium alloys (AZ 61 and AP 65), aluminum alloys (GB 420 and GB 80S) and pure aluminum, in phosphate and borate buffered and unbuffered chloride solutions, are presented and discussed. Anode potentials were found to be simultaneously controlled by more than one oxidation reaction. In the case of the magnesium anodes, the relative contributions of the three oxidation reactions were clearly determined by both the alloy composition and the ambient pressure. In the case of aluminum this was also true, but the actual reactions taking place were more difficult to identify.

The application of DPASV to the determination of the low temperature solubility of lead sulphate in sulphuric acid solutions

“…[4]. The value of the slope will be -AHO/R in moderately concentrated acid solutions and -AH0/2R (by comparison with eq.…”

“…Harned and Hamer (25), whose work yields a value of 2.9 kcal mol-l, formed an adverse opinion of the reliability of this electrode in acid solutions (26). This may be related to the formation of oxides or basic sulphates beneath the oxide layer (4,6). Other emf measurements on the lead -lead sulphate electrode and the lead amalgam -lead sulphate electrode (26) yield values of AH0 of 3.7 and 3.8 kcal mol-I, respectively.…”

“…stronger for a dissolution-precipitation mechanism at the negative than at the positive electrode, both mechanisms appear to be very complicated (3)(4)(5)(6), giving rise to a need for low temperature lead sulphate solubility and dissolution rate data.…”

“…This may be estimated by application of the van't Hoff equation, using values of AH obtained from solubility measurements at higher temperatures, as has been done in order to interpret the low temperature charging kinetics of anodic films on lead in sulphuric acid solutions (5). However, the validity of such an extrapolation remains to be demonstrated experimentally.…”

Significance of effects of pressure on electrode reactions. Part III. Equilibrium processes at reference electrodes and the volume of H in Pd

“…3. evaluation by satisfactory nonthermodynamic means in order that interpretation (3,6) of pressure effects on the kinetics of electrode processes can be made. Reference electrodes reliable at high pressure (2) are also required for evaluation of battery electrode behaviour at high hydrostatic pressures, e.g. in deep marine environments.…”