Evaluation of HC, NOx and NH3 Mixed-Potential Sensors in Diesel and Gasoline Engine Exhaust

Cortney  Kreller, Los Alamos National Laboratory

LANL has developed a patented pre-commercial prototype mixed-potential dual-mode NOx-HC sensor as well as an independent NH3 sensor for application in on-board emissions monitoring and OBD control. The electrochemical sensor design is a derivative of the ubiquitous zirconia based automotive lambda sensor, but incorporates non-equilibrium electrodes to yield selectivity to various exhaust gas constituents.   The unique sensor construct utilizes dense electrodes and a porous electrolyte to provide a robust electrochemical interface, which offers improved stability and a greatly increased lifetime. The dual-mode NOx-HC sensor is based on a La1-xSrxCrO3 working electrode and the ability to shift the preferential selectivity of the device from hydrocarbons to NOx species is achieved by applying a small DC electric current bias. The NH3 sensor utilizes the same sensor platform, but an Au/Pd alloy working electrode is used to gain preferential selectivity to NH3 over other exhaust gas species interferents. The performance of the planar sensors under engine-out conditions has been evaluated at the Oak Ridge National Laboratory National Transportation Research Center on diesel and lean gasoline, multi-cylinder engine platforms. This work will summarize the evaluation of sensor response characteristics in engine exhaust during startup and steady state operation.

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