Stabilization of sensing performance for mixed-potential-type zirconia-based hydrocarbon sensor

Area of Science:

• Materials Science
• Electrochemistry
• Sensor Technology

Background:

• Mixed-potential-type yttria-stabilized zirconia (YSZ)-based hydrocarbon (HC) sensors exhibit performance degradation.
• Operation at 550°C under humid conditions (5 vol.% water vapor) caused significant changes in sensing characteristics after 10 days.

Purpose of the Study:

• To enhance the long-term stability of YSZ-based HC sensors.
• To investigate modifications of the sensing electrode (SE) material for improved performance.

Main Methods:

• Modification of the ZnCr(2)O(4)-sensing electrode (SE) by incorporating YSZ powder.
• Fabrication of a laminated (ZnCr(2)O(4)/YSZ)-SE.
• Evaluation of sensor stability via electromotive force (emf) response over one month.
• Analysis using scanning electron microscopy (SEM) and AC complex-impedance measurements.

Main Results:

• The laminated (ZnCr(2)O(4)/YSZ)-SE sensor showed a stable emf response to 100 ppm C(3)H(6) for approximately one month at 550°C.
• SEM and impedance data indicated that interface stabilization between ZnCr(2)O(4) grains and YSZ particles contributed to the improved stability.
• The sensor demonstrated a linear sensitivity dependence on the logarithm of C(3)H(6) (20-800 ppm) and mixed HC concentrations (90-2600 ppmC).
• The emf response was unaffected by variations in O(2), H(2)O, and CO(2) concentrations, with no observed interference from CO, NO, NO(2), H(2), or CH(4).

Conclusions:

• Lamination of YSZ powder into the ZnCr(2)O(4) sensing electrode significantly enhances the long-term operational stability of mixed-potential-type hydrocarbon sensors.
• The stabilized interface between ZnCr(2)O(4) and YSZ is key to preventing performance degradation under humid conditions.
• The modified sensor offers reliable and selective detection of hydrocarbons in complex gas mixtures.