Enhanced gas sensing performance of tin dioxide-based nanoparticles for a wide range of concentrations of hydrogen gas

Nanocrystalline tin dioxide doped with antimony Sn(Sb)O-2 and catalyzed by 1 wt% palladium has been synthesized by a sonochemical process. On calcination at 600 degrees C, the as-precipitated powder produced 8-10 nm sized Sn(Sb)O-2 nanoparticles. The calcined powder characterized by X-ray diffraction, transmission electron microscopy, specific surface area and X-ray photoelectron spectroscopy was used for thick film sensor unit fabrication. The percentage response of the sensor was more than 78% at and above 200 degrees C for a wide range of concentrations of hydrogen gas. Most of the commercially available sensors are for low ppm values of hydrogen, whereas we were able to establish the response of our sensors for a wide range of concentrations of hydrogen gas from a concentration below 1/10 of the lower explosive limit of hydrogen (4%) in air to a concentration as high as 8% by volume. At 250 degrees C operating temperature, the sensor exhibited nearly 85.5% response towards 0.1% (1000 ppm) hydrogen and 94% response towards 8% hydrogen gas. The fabricated sensor also exhibited better selectivity towards hydrogen than towards other reducing gases like methane and butane. Our results demonstrated that 1% Pd loading has improved the sensor response, lowered the operating temperature and allowed detection of hydrogen in the concentration range of 0.1-8% even in an environment with a relative humidity as high as 88%.