Synergistic enhancement in the sensing performance of a mixed-potential NH3 sensor using SnO2@CuFe2O4 sensing electrode

[Display omitted] •Highly sensitive and NH3 selective mixed-potential type sensor using CuFe2O4 spinel-oxide electrode was firstly developed.•CuFe2O4 and SnO2@CuFe2O4 was successfully synthesized by modified Pechini route.•Sensitivity was critically dependent over the extent of Triple-phase boundary (TPB) lengths and operating conditions.•SnO2@CuFe2O4 electrode displayed a synergistic enhancement in response compared to bare-CuFe2O4 and SnO2 for NH3 detection.•The sensor displayed high sensitivity, NH3 selectivity and excellent long-term stability. A mixed-potential type NH3 sensor equipped with CuFe2O4 and SnO2@CuFe2O4 sensing electrode is presented. The CuFe2O4 spinel-oxide and SnO2@CuFe2O4 composites were synthesized by a modified-Pechini route. The electrode materials were characterized for the physical properties by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) analysis. It was found that the sensing characteristics were critically dependent on the extent of Triple-phase boundary (TPB) lengths and operating conditions of the sensor. Furthermore, the sensing performance of CuFe2O4 spinel-oxide was enhanced by compositing with SnO2 nanocrystals resulting in a synergistically enhanced response (ΔV) of −40 mV towards 80 ppm NH3, almost double and quadruple of the response of bare CuFe2O4 and SnO2 electrodes at 650 ℃, respectively. The sensor also displayed excellent stability towards oxygen and humidity variations, along with low cross-sensitivities towards interfering gases; e.g. NO, CO, CH4, and NO2. The complex impedance spectra (EIS) and dc polarization (I–V) measurements were performed for an insightful analysis of the sensing mechanism conforming to the mixed-potential model.