Sub-ppm H2S sensor based on YSZ and hollow balls NiMn2O4 sensing electrode

A kind of mixed-potential-type gas sensor based on yttria stabilized zirconia (YSZ) and Nickel series spinel structure oxides electrode was designed for detection of low concentration hydrogen sulfide (H2S). Among three oxides (NiMn2O4, NiCr2O4 and NiFe2O4) prepared by solvent evaporation method, hollow balls NiMn2O4 exhibited the highest sensitivity to H2S gas in air at 500 °C. Results of scanning electron microscope (SEM) and X-ray diffraction (XRD) revealed that micro-structure of materials could be influenced by the rate of reagent dropping in the solvent evaporating process and sintering temperature. Then, the relationship between sensing performance and micro-structure of NiMn2O4 was investigated. As a result, the sensor using NiMn2O4 with hollow balls (diameter 5–8 μm) structure as the sensing electrode showed the best performance to 50 ppb to 2 ppm H2S at 500 °C. The ΔV value of the sensing device exhibited segmentally linear relationship to the logarithm of H2S concentration and the slope was −35 mV/decade (50 ppb to 200 ppb) and −125 mV/decade (500 ppb to 2 ppm), respectively. The sensing device also showed an excellent selectivity. Finally, electrochemistry polarization curve measure was taken to further prove the mixed potential sensing mechanism.