Nitrogen oxide responsive element and method for producing same
The present specification provides a NOx responsive element suitable for directly sensing NOx. The NOx responsive element an oxygen ion conductive layer has a first electrode layer having a nitrogen oxide decomposition catalyst phase composed of perovskite-type oxide, being in contact with the oxygen ion conductive layer, and being exposed to NOx, and a second electrode layer opposing the first electrode layer across the oxygen ion conductive layer. The nitrogen oxide decomposition catalyst phase has a nitrogen oxide adsorption stabilizing surface on its surface exposed to nitrogen oxide.
1. A nitrogen oxide responsive element comprising:
an oxygen ion conductive layer;
a first electrode layer having a nitrogen oxide decomposition catalyst phase composed of perovskite-type oxide, being in contact with the oxygen ion conductive layer, and being exposed to NOx, and
a second electrode layer opposing the first electrode layer across the oxygen ion conductive layer,
wherein
the nitrogen oxide decomposition catalyst phase has a surface exposed to nitrogen oxide and the surface includes a nitrogen oxide adsorption stabilizing surface,
the perovskite-type oxide is LaSrMn-based perovskite oxide,
the surface has an MnO 2 termination surface mainly as the nitrogen oxide adsorption stabilizing surface,
the first electrode layer is denser on a side of the oxygen ion conductive layer, and
particle growth of the perovskite-type oxide is suppressed more on a side exposed to nitrogen oxide of the first electrode layer.
2. A nitrogen oxide sensor comprising the element according to claim 1 .
3. A method for producing the nitrogen oxide responsive element according to claim 1 , comprising:
forming the first electrode layer having the nitrogen oxide decomposition catalyst phase composed of perovskite-type oxide on a layer composed of an oxygen ion conductive material,
wherein forming the first electrode layer includes firing a raw material of LaSrMn-based perovskite-type oxide under oxygen rich atmosphere to form the first electrode layer,
wherein the first electrode layer forming is performed so as to form an MnO 2 termination surface mainly as the NOx adsorption stabilizing surface on the surface exposed to nitrogen oxide, and
wherein the first electrode layer forming step includes forming the first electrode layer so that particle growth of the perovskite-type oxide is suppressed more on the surface exposed to nitrogen oxide.