High-temperature potentiometric/amperometric NOx sensors combining stabilized zirconia with mixed-metal oxide electrode
1998; Elsevier BV; Volume: 52; Issue: 1-2 Linguagem: Inglês
10.1016/s0925-4005(98)00270-6
ISSN1873-3077
AutoresNorio Miura, Geyu Lu, Noboru Yamazoe,
Tópico(s)Electrochemical sensors and biosensors
ResumoElectrochemical sensors using stabilized zirconia and oxide electrodes were tested for detecting NO or NO2 potentiometrically and amperometrically at high temperature. For a mixed-potential-type NOx sensor of two-electrode structure, CdCr2O4 was found to give fairly excellent NOx sensing characteristics among the perovskite-type and spinel-type oxides tested. The CdCr2O4-attached device gave a linear correlation between EMF and the logarithm of NO or NO2 concentration at 500–600°C. The mixed potential sensing mechanism was also verified. In order to improve the sensitivity and selectivity to NO, the above device was modified to three-electrode structure. With a fixed bias voltage being applied between the sensing (oxide) and counter (Pt) electrodes, the voltage between the sensing and reference (Pt) electrodes was measured as a sensing signal. The responses to NO and NO2 were found to be enhanced and suppressed with a positive bias, respectively. The tubular device with two-electrode structure was tested for amperometric detection of NOx. A CdCr2O4-attached tubular device was found to show quick and selective response to NO over NO2 at 500 and 550°C, if the oxide sensing electrode was polarized at +100 mV versus the reference Pt electrode. The NOx sensing mechanisms of the three-electrode device were proposed and discussed on the basis of the sensing characteristics obtained.
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