Oxygen electrodes in fused salts: Potentiometric behaviour of the system CO 2, O 2/CO 32− in molten alkali nitrates

Abstract

A potentiometric study on the carbonate electrode (Pt or Au) CO 2, O 2/CO 3 2− was performed at 523 and 623 K in a (Na−K)NO 3 equimolar mixture containing carbonate in the concentration range 10 −5<[CO 3 2−]<10 −2 M and maintained under flux of a mixture of oxygen and carbon dioxide at variable partial pressures ( p O 2 + p CO 2 =1 atm.). While the overal electrode reaction for a carbonate electrode can be expressed by the equation 1 2 O 2 + C O 2 + 2 e = C O 3 2 − ( a ) the present study has shown that the potential taken up by an “indifferent electrode” can be described by the equation E = const. + ( R T / 2 F ) 1n { [ C O 2 ] / [ C O 3 2 − ] } ( b ) The apparent potentiometrically irreversible behaviour of the carbonate electrode under the given experimental conditions has been interpreted on the basis of a mechanistic model involving, in the potential-determining step, the oxidized surface of the noble metals. For example [Display omitted]