Compact electrochemical bifunctional NOx/O2 sensors with internal reference for high temperature applications

A bi-functional sensor for sensing NOx and O2 in a high temperature environment comprising:

• a chamber comprising yttria-stabilized zirconia (YSZ) and forming an exterior surface and a substantially closed internal volume;
• a first electrode disposed within the internal volume and including a lead wire having a first end operatively connected to the YSZ, and a second end extending from the external surface;
• a quantity of a mixture of a transition metal and an oxide of the transition metal disposed within the internal volume;
• a quantity of Pt-zeolite Y disposed on the exterior surface of the chamber;
• a second lead wire having a first end operatively connected to the quantity of Pt-zeolite Y and a second end operatively connected to a potential source;
• and
• a third lead wire operatively connected to the quantity of Pt-zeolite Y,
• wherein a current at the second and third electrodes is indicative of the concentration of NOx proximate the external surface, and wherein a potential between the first electrode and the third electrode is indicative of the concentration of O2 proximate the external surface.

A method of simultaneously sensing a concentration of NOx and O2 comprising:

• providing a bi-functional sensor comprising a chamber forming a substantially closed internal volume and an external surface, a quantity of a reference material disposed within the internal volume, and a first electrode disposed within the internal volume, and a plurality of electrodes operatively coupled to the external surface of the chamber;
• exposing the sensor to an atmosphere comprising a plurality of gases generated in a combustion environment;
• obtaining a first electrical response from two or more of the plurality of electrodes indicative of the concentration of NOx in the combustion environment;
• and
• obtaining a second electrical response from the first electrode and one or more of the plurality of electrodes indicative of the concentration of O2 in the combustion environment.