Comparative study of nanocrystalline SnO2 materials for gas sensor application: Thermal stability and catalytic activity

In this paper we discuss thermal stability of tin dioxide nanoparticles and long-term stability of the SnO2-based gas sensors. Relying on laser-spark element analysis and XRD analysis we compare crystallite growth kinetics of synthesized and commercial (Sigma–Aldrich) SnO2 with different impurity level. We found that commercial SnO2 nanopowder has lower thermal stability in comparison with synthesized one, resulting in higher crystallite growth rate and poly-dispersed particle size after annealing. A special attention is drawn to discussion of catalytic activity of the nanocrystalline materials. Using IR spectroscopy we studied chemical composition of the annealed materials, which allowed us to reveal in the synthesized SnO2 intensive formation of Sn–OH bonding during annealing. We performed temperature programmed reduction (TPR) analysis to compare the catalytic activity of the materials with and without deposited Pd on SnO2. Long-term stability of the sensors made on the basis of synthesized and commercial SnO2 was measured as a sensor signal deviation during 590 h of operation in 0.2, 0.6 and 1.0 vol. % of propane in air (50% RH at 20 °C).