Surface decorated spinel-oxide electrodes for mixed-potential ammonia sensor: Performance and DRT analysis

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Sensing

Background:

• Mixed-potential gas sensors offer a promising, low-cost solution for in-situ exhaust pollutant monitoring.
• Commercialization is hindered by challenges in achieving high sensitivity, selectivity, and long-term stability.

Purpose of the Study:

• To develop highly sensitive and ammonia (NH3)-selective mixed-potential gas sensors.
• To investigate the performance of surface-decorated CuFe2O4 (CFO)-MOx composite electrodes for NH3 detection.

Main Methods:

• Fabrication of CuFe2O4 (CFO)-MOx (M=Sn, Ni, Zn) composite sensing electrodes.
• Testing sensor response and selectivity to NH3 at 650 °C.
• Analysis of current-voltage (I-V) characteristics and impedance spectra using distribution of relaxation times (DRT).

Main Results:

• The CFO-NiO electrode exhibited a maximum response of -62 mV to 80 ppm NH3 with excellent sensitivity.
• Sensing mechanism confirmed to be mixed-potential, governed by reaction-rate limited Butler-Volmer kinetics.
• DRT analysis indicated polarization resistance is controlled by interfacial redox reactions at triple-phase boundaries (TPB).

Conclusions:

• The developed CFO-NiO sensor demonstrates high sensitivity, selectivity, and exceptional stability over five months.
• This sensor is a suitable candidate for in-situ ammonia quantification in industrial and automotive applications.
• Surface decoration with oxygen vacancies enhances sensor performance for pollutant monitoring.