To increase the sensitivity of internal combustion engine exhaust gas sensors, which provide a voltage jump output upon transition of the composition of the exhaust between reducing and oxidizing state, and to maintain the porosity of a platinum, or platinum metal alloy layer forming an electrode on a body of zirconium dioxide, the electrode or electrode layer has dispersed therein an oxide or a carbide of a metal which impedes or inhibits recrystallization at the temperatures to which the sensor is exposed, for example 1000.degree. C., typically zirconium, titanium, tantalum, niobium, aluminum or thorium oxide, or titanium or tantalum carbide, applied, for example, by sequential vaporization of platinum or a platinum metal alloy and the respective metal forming the oxide, in an atmosphere containing residual oxygen, and then oxidizing the remaining metal being applied; or by simultaneous application of a carbide and platinum, for example during simultaneous cathodic atomization, or electron beam vaporization of the respective materials, to form a porous electrode layer of about 2-3 .mu.m thickness, containing approximately 5-40 mol-% of the recrystallization-inhibiting material and having a square resistance not exceeding 20 ohm-square resistance.