Metallic Cavity Electrodes for Investigation of Powders

Metallic cavity electrodes (MCEs) for quick electrochemical investigations of powders in high-temperature molten salts are described. Molybdenum foils (thickness ; width 1.0–2.0 mm; length 100–150 mm) were tested with one or two cavities of through circular holes (diameter 0.3–1.0 mm) filled with submilligrams of the fine powder of NiO or in molten at 1173 K. Cyclic voltammograms exhibited features of thin-layer or chemically modified electrodes with irreversible reactions. Charge-transfer coefficients for the electroreduction of both NiO and were estimated to be much smaller than 0.5. Chronoamperometry demonstrated fast cathodic conversion, in a time of the order of magnitude of , of the oxide powders to the respective metals inside the cavity, as confirmed by scanning electron microscopy and energy-dispersive X-ray. The results also suggested electrochemically driven interactions between the oxide and the and ions in the molten salt before oxygen removal.