Gas sensing properties of TiO2-SnO2 nanomaterials

Nanocomposites of TiO2/SnO2 for hydrogen detection have been prepared by mechanical mixing of TiO2 and SnO2 nanopowders with different specific surface area SSA = 150.9 m2/g (TiO2) and SSA = 18.3 m2/g (SnO2). Nanocomposites consist of two distinct components: larger - grain (21-28 nm) cassiterite SnO2 and smaller - grain (8-11 nm) rutile TiO2 as indicated by X-ray diffraction measurements and transmission electron microscope, TEM, images. Nanopowders of 50 mol% TiO2/50 mol% SnO2 are composed of small, elongated TiO2 forms mixed with larger SnO2 grains of regular shape as demonstrated by TEM. Scanning electron microscopy, SEM of gas sensing tablets, prepared by pressing nanopowders under 25 MPa at 400 °C reveal a high degree of agglomeration. Sensor responses in the electrical resistivity over a wide range of concentrations from 50 to 3000 ppm H2 at a constant temperature chosen within the interval 250-400 °C have been measured and analyzed before and after sample conditioning at 500 °C in Ar + 7% H2 atmosphere. Sensing tablets of 50 mol% TiO2/50 mol% SnO2 display the highest sensitivity to hydrogen at moderate temperatures of 250-300 °C. Kinetics of the sensor responses are improved and the recovery time is significantly reduced as a result of annealing in the reducing atmosphere.