HYDROCARBON SENSOR FOR MONITORING EXHAUST GAS USING OXYGEN PUMPING CURRENT

摘要

Amperometric type hydrocarbon sensor using a single electrolyte plate of Ni doped LaGaO_3 based oxide was investigated for monitoring exhaust gas from an internal combustion engines. Compared to a simple mixed potential type sensor, amperometric sensor using oxygen pumping current shows a wider range for hydrocarbon detection. In particular, current at 1 V application was mainly affected by hydrocarbon but not oxygen when Pt and La_(0.6)Sr_(0.4)CoO_3 were used as active and inactive electrode for oxidation of hydrocarbon, respectively. Since the current linearly increased with increasing hydrocarbon, it is expected that the concentration of hydrocarbon in exhaust gas can be monitored with the current through the sensor element. The current of the developed sensor is hardly influenced by coexisting CO and H_2O and is only slight influenced by O_2. Therefore, selective detection of hydrocarbon is expected. In addition, the sensitivity to hydrocarbon increased with increasing carbon number in the hydrocarbon and the sensitivity to CH4 is negligibly small. Consequently, the developed amperometric hydrocarbon sensor can detect hydrocarbon excepting CH_4 with high selectivity. This is a suitable property for a sensor used to monitor hydrocarbon content in the exhaust gas from internal combustion engines.