CO DETERMINATION IN AIR BY YSZ-BASED SENSORS

Potentiometric solid state ps sensors have been developed for CO monit oring in air. The following galvanic cell was investigated: Pt\M, (CO + O2)\ZrO2-Y2O3\(O2), Pt\Pt where M is either a Pt or an RuO2 layer. S ensors were characterized between 350 and 650-degrees-C with carbon mo noxide partial pressures ranging from 1 to 80 Pa. A linear relationshi p between the electromotive forces (e.m.f.s) and log(p(CO)) was observ ed. The e.m.f. versus time curve can be described by: \E(t) - E(infini ty)\/\E(0) - E(infinity)\ = exp[-(t/tau)n] where E(0) and E(infinity) are the values at the time at which the pressure of CO is abruptly cha nged (taken as t = 0) and that at which steady-state conditions are re ached. Tau is a time constant and n is an adimensional exponent. Resul ts obtained with Pt and RuO2 electrode materials are compared and disc ussed.