NOx Sensor with Dual Catalytic Coatings for Selective Detection
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Solution Overview
Problem
Current nitrous oxide sensors, particularly those based on ion conductor technology, are not satisfactory for detecting NOx levels in the 1 to 2000 ppm range without cross-sensitivity to other gases, posing challenges in controlling NOx emissions in combustion processes.
Innovation Solution
A nitrous oxide sensor with two sensing circuits sharing a common electrode, differentiated by porous catalytic filter coatings containing either a Noxcat material (rhodium, ruthenium, cobalt, palladium, or nickel) or being substantially free of it, measures NOx levels by detecting resistance differences due to oxygen exposure variations caused by the catalytic action, allowing for accurate NOx detection and control of exhaust systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrochemical sensors based on ion conductor technology are used for NOx detection, then the sensor can detect NOx levels, but the sensor experiences cross-sensitivity to other gases (H2, CO, sulfur compounds, etc.)
Solution Approach 1:
The sensor is divided into two separate sensing circuits: one circuit contains a porous catalytic filter coating with Noxcat material that selectively converts NOx to O2, while the other circuit has a substantially free porous catalytic filter coating from Noxcat material. This segmentation allows each circuit to respond differently to NOx, enabling selective detection while filtering out cross-sensitivity to other gases.
Solution Approach 2:
The porous catalytic filter coating acts as an intermediary between the exhaust gas and the metal oxide semiconductor sensing material. The Noxcat material in the coating selectively catalyzes the conversion of NOx to O2 before the oxygen reaches the sensing material, thereby mediating the detection process to eliminate cross-sensitivity to other gases that would otherwise interfere with direct sensing.
2Adaptability or versatility
If a single sensing circuit is used, then the device complexity is low, but the ability to distinguish NOx from other gases is insufficient
Solution Approach 1:
The sensor is divided into two separate sensing circuits: one circuit contains a porous catalytic filter coating with Noxcat material that selectively converts NOx to O2, while the other circuit has a substantially free porous catalytic filter coating from Noxcat material. This segmentation allows each circuit to respond differently to NOx, enabling selective detection while filtering out cross-sensitivity to other gases.
Solution Approach 2:
Both sensing circuits share a common electrode and are exposed to the same exhaust gas environment, merging the measurement function while differentiating the catalytic response. This combining approach allows for differential measurement that enhances selectivity without requiring completely separate sensor systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor effectively determines NOx levels in exhaust gases, enabling precise control of NOx traps and reducing environmental impact by minimizing cross-sensitivity to other gases, thus improving NOx emission management in internal combustion engines and burner systems.
Implementation Method 1
one sensing circuit has a porous catalytic filter coating that contains a nitrous oxide catalyzing or 'Noxcat' material
Implementation Method 2
The NOx level can be determined based on a difference in resistance between the two sensing circuits
Data Source
AI summary
Nitrous oxide (NOx) sensors and related methods and systems for use with combustion processes. The NOx sensor uses metal oxide semiconductors. The NOx sensor may have two sensing circuits that share a common electrode. The sensing circuits are differentiated by having different porous catalytic filter coatings protecting the metal oxide semiconductors: one sensing circuit has a porous catalytic filter coating that contains a Noxcat material (rhodium, ruthenium, cobalt, palladium, or nickel), while the porous catalytic filter coating of the other sensing circuit is substantially free of Noxcat material. The two sensing circuits are simultaneously exposed to the exhaust gases at a common macro location. The NOx level may be determined based on a difference in resistance between the two sensing circuits and a temperature of the NOx sensor.