Stabilized zirconia-based sensor utilizing SnO2-based sensing electrode with an integrated Cr2O3 catalyst layer for sensitive and selective detection of hydrogen

A highly selective hydrogen (H2) sensor has been successfully developed by using an yttria-stabilized zirconia (YSZ)-based mixed-potential-type sensor utilizing SnO2 (+30 wt.% YSZ) sensing electrode (SE) with an intermediate Al2O3 barrier layer which was coated with a catalyst layer of Cr2O3. The sensor utilizing SnO2 (+30 wt.% YSZ)-SE was found to be capable of detecting H2 and propene (C3H6) sensitively at 550 °C. In order to enhance the selectivity towards H2, a selective C3H6 oxidation catalyst was employed to minimize unwanted responses caused by interfering gases. Among the examined metal oxides, Cr2O3 facilitated the selective oxidation of C3H6. However, the addition or lamination of Cr2O3 to SnO2 (+30 wt.% YSZ)-SE was found to diminish the sensing responses to all examined gases. Therefore, an intermediate layer of Al2O3 was sandwiched between the SE layer and the catalyst layer to prevent the penetration of Cr2O3 particles into the SE layer. The sensor using SnO2 (+30 wt.% YSZ)-SE coated with a catalyst layer of Cr2O3 as well as an intermediate layer of Al2O3 exhibited a sensitive response toward H2, with only minor responses toward other examined gases at 550 °C under humid conditions (21 vol.% O2 and 1.35 vol.% H2O in N2 balance). A linear relationship was observed between sensitivity and H2 concentration in the range of 20–800 ppm on a logarithmic scale. The results of sensing performance evaluation and polarization curve measurements indicate that the sensing mechanism is based on the mixed-potential model. ► Sensitive and selective detection toward H2 using YSZ-based mixed potential sensor. ► Linear relationship between sensing signal and logarithm of H2 concentration within 20–800 ppm. ► Response time for 100 ppm H2 in air was approximately 10 s. ► The sensitivity was independent to changes in water vapor (1–5 vol.% H2O). ► Al2O3 isolation layer facilitated integration of the catalyst and SE in one device.