Fast Responding Amperometric CO₂ Microsensor with Ionic Liquid-Aprotic Solvent Electrolytes.

Area of Science:

• Electrochemistry
• Environmental Science
• Sensor Technology

Background:

• Accurate microscale carbon dioxide (CO₂) distribution knowledge is crucial for environmental and technical applications.
• Electrochemical CO₂ sensors offer a pathway to obtain this microscale information.
• Previous Clark-type CO₂ sensors utilized 1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA) as an electrolyte.

Purpose of the Study:

• To enhance the performance of a Clark-type CO₂ sensor.
• To investigate the effect of adding dimethylformamide (DMF) to the EMIM-DCA electrolyte.
• To evaluate the sensor's response time, interference, temperature dependence, and long-term stability.

Main Methods:

• A Clark-type CO₂ sensor was modified by incorporating 20% dimethylformamide (DMF) into the 1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA) electrolyte.
• Electrochemical performance was assessed, including response to varying CO₂ concentrations, interference from N₂O, and signal dependence on temperature.
• CO₂ reduction potential and sensor stability were measured over continuous polarization.

Main Results:

• The addition of 20% DMF significantly accelerated sensor response time (95% response in ~100 s) and reduced CO₂ overpotential by 0.2 V.
• The modified sensor demonstrated negligible interference from low N₂O concentrations and exhibited temperature dependence similar to O₂ microsensors.
• The sensor achieved a limit of detection of 0.5 Pa CO₂, a linear response range of 0-4.6 kPa, and maintained stable zero current and sensitivity over 4 months.

Conclusions:

• The 80% EMIM-DCA/20% DMF electrolyte significantly enhances Clark-type CO₂ microsensor performance.
• This optimized sensor provides faster, more accurate, and stable measurements for microscale CO₂ detection.
• The improved sensor is suitable for diverse environmental and technical applications requiring precise CO₂ monitoring.