Fast Response, Highly Sensitive and Selective Mixed-Potential H₂ Sensor Based on (La, Sr)(Cr, Fe)O_3-δ Perovskite Sensing Electrode

A planar mixed-potential type sensor consisting of La 0.8 Sr 0.2 Cr 0.5 Fe 0.5 O 3-δ 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 °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 °C for 500 ppm. The sensor exhibited excellent selectivity to hydrogen against interference of CH 4, C 3 H 8, CO, NO 2, and NH 3 . 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.