Sub-ppb SO_2 gas sensor based on NASICON and La_xSm_(1-x)FeO_3 sensing electrode

摘要

Highlights•A series of sensing electrode materials La1-xSmxFeO3(x=0.2, 0.4, 0.5, 0.6 and 0.8) were first developed to fabricate NASICON-based mixed-potential SO2sensors.•The sensor utilizing La0.5Sm0.5FeO3-SE gave the largest response value (-86.5mV) to 1ppm SO2, and the lowest detection limit could reach to 5 ppb.•The sensitivities of the fabricated sensor in the ranges of 0.005–0.2ppm and 0.2–5ppm, were −8 and −86mV/decade, respectively.•The sensor displayed good reliability, stability and selectivity.AbstractA NASICON-based mixed-potential gas sensor utilizing the perovskite-type orthoferrite LaxSm1-xFeO3(x=0.2, 0.4, 0.5, 0.6, 0.8) sensing electrode (SE) was designed for SO2detection. The research mainly put emphasis on the effect of different La3+doping ratios in LaxSm1-xFeO3on the sensing characteristics, and the highest response value (-86.5mV) to 1ppm SO2was observed for the sensor using La0.5Sm0.5FeO3-SE. The response value of the fabricated sensor displayed segmentally linear relationship with the logarithm of SO2concentration in the ranges of 0.005-0.2ppm and 0.2–5ppm, and the slopes were −8 and −86mV/decade, respectively. Otherwise, the low detection limit of the present sensor even could reach to 5ppb with an accurate response value (-8.4mV). Meanwhile, the sensor also showed good repeatability, long-term stability and selectivity toward other interfering gases. Furthermore, the electrochemical impendence curves indicated the reason that the sensor attached with La0.5Sm0.5FeO3-SE displayed the higher response values than the other sensors. The result indicated that differences of electrocatalytic activity was caused by diverse La3+doping content in sensing electrode. The sensing mechanism related to the mixed potential was demonstrated by the polarization curve.