The effect of porosity on the CO sensing properties of TiO2 xerogel thin films

TiO2 gas sensing materials based on nanostructured xerogel were produced by a solvothermal drying process. The CO sensing ability of the anatase form of TiO2 was evaluated at a temperature of 350 °C. TiO2 xerogel thin films with high surface areas and different porosities were annealed at 450 °C under vacuum. The crystallite sizes and ceramic microstructures of the powders were analyzed by scanning electron microscopy, and the crystal structures of the powder were obtained from X-ray diffraction patterns. Fourier transform infrared spectroscopy was used to investigate the chemical bonding of the TiO2 xerogel films. Structural and morphological studies were carried out in order to investigate their influences on the sensing properties of the TiO2 xerogel thin films. The sensing behavior of anatase TiO2 toward CO in an oxidizing environment was studied in order to understand the basis for CO sensing. The CO sensing properties of TiO2 xerogel thin films varied depending on their porosity, i.e., specific surface area.

► TiO2 xerogels were synthesized by sol–gel method using solvothermal drying.
► CO gas sensing ability of TiO2 xerogel was studied.
► CO gas sensitivity of TiO2 xerogel films depends on the porosity of the xerogels.
► A sensitivity of 6.8 was obtained with a TiO2 xerogel film of 62% porosity.