A study of the Ag(s)/Ag2SO4(l) high temperature reference electrode

Abstract

AbstractAg(s)/Ag2SO4(l) reference electrodes for use in hot corrosion research were fabricated and their properties were studied at 927°C (1200°K). The McDanelTM MV 30 mullite tube was used as sheath of the reference electrode and concentrations of the tested electrolytes were varied from 0.1 to 10 m/o Ag2SO4 (l) + Na2SO4 (l). 10 m/o Ag2SO4 was always used as electrolyte in the reference electrode. The working electrodes with less than 2 m/o Ag2SO4 showed marked potential drift as the Ag2SO4 concentration was lowered, showing poor potential stability. However, the initial values of cell voltages obeyed Nernstian behavior for all range of Ag2SO4 concentrations in the working electrodes, which showed that Ag(s)/Ag2SO4(l) electrodes behaved reversibly. Galvanostatic polarization was performed on a pair of 10 m/o Ag2SO4 reference electrodes to test the reversibility. The polarizability was 3.5 mV/10 μA with no hysteresis loop on the polarization curve, showing that the reversibility was satisfactory. The potential of gold electrode in molten Na2SO4 was measured under pure oxygen atmosphere with 10 m/o Ag2SO4 electrode as a reference potential. The results showed that the potential of gold electrode could be explained by the 2 Na + SO3 + 1/2 O2 → Na2SO4 cell reaction.