Gradient Oxygen Pump Electrode for NOx Detection Accuracy
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Solution Overview
Problem
Conventional gas sensors experience a decrease in NOx detection accuracy due to NOx decomposition in the pump electrode when high oxygen concentrations are present, leading to reduced NOx detection accuracy.
Innovation Solution
A sensor element design with an inner oxygen pump electrode having a region close to the gas inlet with a higher content of activity-reducing metals, such as gold, to suppress NOx decomposition, maintaining high NOx detection accuracy even under high oxygen concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional pump electrode material is used to remove oxygen, then oxygen removal efficiency is improved, but NOx decomposition occurs leading to decreased detection accuracy
Solution Approach 1:
The pump electrode is designed with a gradient structure where the metal content increases from the upstream side (near gas inlet) to the downstream side. This local variation in material composition allows the upstream region to have lower catalytic activity and prevent NOx decomposition, while the downstream region maintains high oxygen removal efficiency.
Solution Approach 2:
The invention changes the physical parameter of metal content distribution in the pump electrode. By creating a gradient where metal content increases from upstream to downstream, the electrode achieves different functional characteristics in different regions, solving the contradiction between oxygen removal efficiency and NOx detection accuracy.
2Productivity
If the pump electrode is positioned close to the gas inlet for effective oxygen removal, then oxygen concentration control is improved, but NOx decomposition increases due to high local voltage
Solution Approach 1:
The pump electrode incorporates a gradient metal content structure where the upstream portion (close to gas inlet) has lower metal content and thus lower catalytic activity, preventing NOx decomposition in the high-voltage region. The downstream portion has higher metal content for effective oxygen removal.
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 element effectively suppresses NOx decomposition and maintains high NOx detection accuracy regardless of oxygen concentration levels, ensuring reliable NOx detection.
Implementation Method 1
a base part in an elongated plate shape, including a plurality of oxygen-ion-conductive solid electrolyte layers stacked
Implementation Method 2
an inner oxygen pump electrode disposed on an inner surface of the measurement-object gas flow part
Implementation Method 3
the metal material including an activity reducing metal that reduces catalytic activity of decomposing NOx
Data Source
AI summary
A sensor element includes a base part including a plurality of oxygen-ion-conductive solid electrolyte layers stacked; a measurement-object gas flow part for introduction and flow of a measurement-object gas through a gas inlet; an inner oxygen pump electrode disposed on an inner surface of the measurement-object gas flow part; and a measurement electrode disposed on the inner surface of the measurement-object gas flow part. The inner oxygen pump electrode includes: a region (A) including an electrode end close to the gas inlet, and a region (B) including an electrode end far from the gas inlet. A content rate of an activity reducing metal in a metal material in the region (A) is higher than that in the region (B). A ratio of the length of the region (A) of the inner oxygen pump electrode to the length of the inner oxygen pump electrode is 15% to 90%.