Oxygen electrodes in fused salts. Potentiometric and X-ray photoelectron spectroscopic (ESCA) findings on the system (Ni)Co2+ O2/CO 2–3 in molten nitrates

Abstract

Potentiometric data recorded as a function of temperature and time on the system (Ni)CO₂+ O₂/CO^2–₃ in nitrate melts are compared with ESCA findings obtained on nickel sheets maintained under the same experimental conditions as the nickel electrodes. Noticeable variations in the potential were observed to correspond to the larger modification of ESCA spectra due to the formation of nickel species at different oxidation states. The chemical reactions responsible for microcorrosion of the electrode surface and the electrode mechanisms involving the formed surface compounds (nickel oxides and carbonates) are critically discussed in the light of the observed experimental results.