Mixed Potential-Based Miniature Sensors for Real-Time On-Vehicle NOx Monitoring From Mobile Sources

Nitric oxide and nitrogen dioxide (jointly represented as NOx) constitute one of the primary classes of pollutants in engine exhaust from both on-road mobile sources such as diesel trucks, and off-road sources such as tractors. Monitoring the NOx concentration in exhaust streams is critical for efficient application of new technologies for the reduction of NOx emissions, and for the enforcement of emissions regulations by the U.S. Environmental Protection Agency (EPA). However, current sensors will not perform or survive in the expected operating conditions (i.e., in hot gases with a range of 450-550¿C, found in engine exhaust). Therefore, there is a need for the development of robust sensors that can perform for extended periods under such conditions. In the proposed work, a novel, mixed potential-based miniature sensor with a high temperature performance capability combined with other requirements such as high sensitivity, fast response time, and little cross-sensitivity with other gases in the exhaust stream will be developed. The sensor will be fabricated through conventional, cost-effective, ceramic fabrication techniques, and enhanced performance will be achieved through a combination of system design and materials selection based on the basic working principles of mixed-potential sensors. This will be followed by testing of the performance of these sensors under simulated operating conditions by a leading diesel engine manufacturer, at no direct cost to the research project. The proposed sensor is expected to allow online monitoring of NOx concentrations in mobile sources such as diesel trucks, thereby allowing real-time process modification, which is a requirement for highly efficient NOx emissions reduction. The successful development of this technology will allow for significant NOx emissions reductions from mobile sources, and for the enforcement of emissions regulations by the EPA. Because it is estimated that compliance with new EPA regulations can lead to a reduction of up to 686,000 tons of NOx per year by 2010, monitoring and enforcement of NOx emissions using the proposed technology can have a significant impact on the environment. Furthermore, this sensor design is generic and can be adapted to monitor other stack and exhaust gases through the selection of appropriate electrode/electrolyte systems. It also is anticipated that, due to Ceramatec, Inc.¿s collaboration with a potential user/customer of the technology from the start of the research project, the potential for commercialization of the technology is very high.