Fast Response, Highly Sensitive and Selective Mixed-Potential H2 Sensor Based on (La, Sr)(Cr, Fe)O3-δ Perovskite Sensing Electrode.

A planar mixed-potential type sensor consisting of La0.8Sr0.2Cr0.5Fe0.5O3-δ sensing electrode, yttria-stabilized zirconia solid electrolyte, and Pt reference electrode was developed for H2 detection. The sensor showed high and repeatable response with a value of -143.6 mV for 1000 ppm of H2 at 450 °C. The sensor response varied linearly or logarithmically with the hydrogen concentration in the range of 20-100 ppm and 100-1000 ppm of H2, respectively. The response/recovery time generally decreased with increasing concentration and temperature, and reached almost steady above 300 ppm of H2. Response time as short as 4 s and recovery time of 24 s were attained at 450 °C for 500 ppm. The sensor exhibited excellent selectivity to hydrogen against interference of CH4, C3H8, CO, NO2, and NH3. The mixed-potential mechanism was assessed by electrochemical measurements, and the sensing behavior was discussed in relation to the reaction kinetics. The excellent H2 sensing performance for concentrations above 100 ppm is ascribed to the high electrocatalytic activity of the perovskite electrode to H2 oxidation. The inferior performance for lower H2 concentrations may be related with slow gas diffusion in the electrode.