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.delta sensing electrode, yttria-stabilized zirconia solid electrolyte, and Pt reference electrode was developed for H-2 detection. The sensor showed high and repeatable response with a value of -143.6 mV for 1000 ppm of H-2 at 450 degrees C. The sensor response varied linearly or logarithmically with the hydrogen concentration in the range of 20-100 ppm and 100-1000 ppm of H-2, respectively. The response/recovery time generally decreased with increasing concentration and temperature, and reached almost steady above 300 ppm of H-2. Response time as short as 4 s and recovery time of 24 s were attained at 450 degrees 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 H-2 sensing performance for concentrations above 100 ppm is ascribed to the high electrocatalytic activity of the perovskite electrode to H-2 oxidation. The inferior performance for lower H-2 concentrations may be related with slow gas diffusion in the electrode.