Novel NASICON-based H2 sensor with insensitive reference electrode and buried Au sensing electrode

A mixed potential type sensor based on NASICON (sodium super-ionic conductor) was designed for the detection of hydrogen. Two original ways were combined to promote the sensor's sensitivity. LaCrO3 was applied on Au reference electrode as H2 oxidation layer to minimize the H2 response on reference electrode. Additional NASICON layer was coated on Au sensing electrode serving as sensitive electrode for limiting the O2 diffusion. H2 temperature-programmed reduction (TPR) measurement was conducted to test the oxidizability of LaCrO3. The effect of O2 concentration on sensor's sensitivity was discussed to verify the function of additional NASICON layer. The correlation between the thickness of additional NASICON diffusion layer and sensor's sensitivity was also studied. The research showed that the sensor attached with 0.3 mm thick additional NASICON layer exhibited the largest sensitivity to 100-5000 ppm H2 at 400 °C, the slope was −123 mV/decade. In addition, the sensor exhibited excellent selectivity to H2 against the other interference gases, such as CO, NO2, NH3, C7H8, C2H4, CH2O, C3H6O and CH4.