Electrochemical device incorporating means for preventing reduction of

Abstract

An electrochemical device having an oxygen-ion conductive solid electrolyte body, a plurality of electrodes formed on the solid electrolyte body, an electrically insulating ceramic layer formed on the solid electrolyte body, a heater disposed such that the heater is electrically insulated by the ceramic layer from the solid electrolyte body, and a dc power source electrically connected to the heater for energizing the heater. At least one of the electrodes is electrically connected to a low-potential terminal of the dc power source. A voltage source is connected in a line between the above-indicated at least one electrode and the low-potential terminal of the dc power source, so that a potential of each of the at least one electrode with respect to a potential V1 at a point of connection of the above-indicated line to the low-potential terminal of the dc power source is maintained at a positive value which satisfies a formula, V1.ltoreq.V2+V3, where, V2 represents voltage drop between a low-potential terminal of a heat-generating portion of the heater and the point of connection to the low-potential terminal of the dc power source, which occurs due to the heating current applied to the heat-generating portion, and V3 represents decomposition potential of the ceramic layer or the solid electrolyte body, whichever is lower, where the at least one electrode operates as an anode.