Impurity level in SnO₂ materials and its impact on gas sensing properties

Using the same protocol for precipitation of tin hydroxide and its hydrothermal treatment (HT), we synthesize SnO₂ from three precursors - tin(IV) acetate, tin(IV) hydroxide acetate and tin(IV) chloride pentahydrate. After annealing on sensor substrates the materials were found to be very similar from structural point of view. However, their sensing properties (responses to CO and H₂ as a function of humidity) were discovered to be very different, which was related to different impurity level in the samples. High amount of chlorine and potassium (ca. 300 ppmw) in two samples corresponded well to notably high water vapor effect. Differences in surface areas (within 20-60 m²/g) and pore volumes (between 0.11 and 0.19 cm³/g), found for the materials in question, seem to play minor role if the impurities are present.