A study of the Ag(s)/Ag 2 SO 4 (l) high temperature reference electrode

Ag(s)/Ag 2 SO 4 (l) reference electrodes for use in hot corrosion research were fabricated and their properties were studied at 927°C (1200°K). The McDanel TM 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 Ag 2 SO 4 (l) + Na 2 SO 4 (l). 10 m/o Ag 2 SO 4 was always used as electrolyte in the reference electrode. The working electrodes with less than 2 m/o Ag 2 SO 4 showed marked potential drift as the Ag 2 SO 4 concentration was lowered, showing poor potential stability. However, the initial values of cell voltages obeyed Nernstian behavior for all range of Ag 2 SO 4 concentrations in the working electrodes, which showed that Ag(s)/Ag 2 SO 4 (l) electrodes behaved reversibly. Galvanostatic polarization was performed on a pair of 10 m/o Ag 2 SO 4 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 Na 2 SO 4 was measured under pure oxygen atmosphere with 10 m/o Ag 2 SO 4 electrode as a reference potential. The results showed that the potential of gold electrode could be explained by the 2 Na + SO 3 + 1/2 O 2 → Na 2 SO 4 cell reaction.