Use of air/platinum as the reference electrode in solid oxide electrolyte e.m.f. measurements

The electrode, air (PO2≈21.222 kPa)/Pt is often used as a reference electrode in numerous applications in oxygen gauges and coulometric devices which make use of zirconia based solid electrolytes. In recent years, a large number of thermodynamic measurements have been reported using the zirconia electrolyte based e.m.f. technique with this reference electrode. This review summarizes the merits, limitations, mechanistic aspects, precautions to be taken and the sources of error in the use of air/Pt electrode for thermodynamic measurements. In addition, a brief survey of recent applications of air/Pt electrode is presented, together with recommendations for the proper use of the omnipresent air as an oxygen fugacity standard.