High-Temperature CO₂ Sensor with Second-Level Response for Diesel Engine Exhaust Gas Detection Applications

Area of Science:

• Materials Science
• Electrochemistry
• Environmental Science

Background:

• Diesel engines are significant CO2 emitters, but accurate emissions calculation is challenging due to incomplete combustion and harsh exhaust conditions.
• Existing sensors struggle with the high temperatures, response speed, and stability required for real-time exhaust gas monitoring.

Purpose of the Study:

• To develop a high-performance sensor for accurate in-situ carbon dioxide (CO2) detection in diesel engine exhaust.
• To enhance sensor sensitivity, response speed, and high-temperature resistance for practical automotive applications.

Main Methods:

• Co3O4 was doped into Na2CO3 as a catalyst and stabilizer, and NASICON solid electrolyte was used to improve sensor performance.
• A doped Na2CO3-NASICON sensor was fabricated and tested for CO2 response, selectivity, humidity, and long-term stability.
• An in-situ on-board CO2 sensing probe and test system were developed and calibrated against standard instruments for vehicle testing.

Main Results:

• The optimized sensor (10 wt% Na2CO3 and NASICON) achieved a -67 mV response to 5000 ppm CO2 with a second-level full-range response.
• The sensor demonstrated a wide detection range (0-180,000 ppm), high sensitivity (-64 mV/decade), good CO2 selectivity, and negligible response to humidity (20-98% RH).
• Long-term stability (60 days) showed only an -8.66% change, with good reproducibility and practical on-board testing showing <10% deviation from standard instruments.

Conclusions:

• The developed Co3O4-doped Na2CO3-NASICON sensor offers a practical solution for accurate, real-time CO2 monitoring in diesel exhaust.
• The sensor's rapid response, wide detection range, stability, and selectivity meet the demanding requirements for on-board automotive emissions analysis.
• The successful in-situ testing validates the sensor's potential for real-world application in vehicle exhaust gas detection and environmental monitoring.