Modelling Of Gas Diffusion In Mesoporous Tin Oxide (SnO2) Based Gas Sensor Effect Of Operating Temperatures And Gas Concentration

The sensitivity of a mesoporous tin oxide gas sensor has been theoretically investigated in relation to gas diffusion phenomena. Diffusion models that comprises original and modified diffusion models were created by using MATLAB with the assumption that the target gas which is the inflammable gas flows inside the film is driven by Knudsen diffusion and react with adsorbed oxygen species via a first-order kinetic reaction. Theoretically, the sensitivity of the gas sensor depicts a bell-curved with the variations of operating temperatures. Whilst, the sensitivity increases with the gas concentrations and subsequently became saturated. However, the original diffusion model unable to predict both trends. The modification of the former equation of diffusion model was carried out in which the film conductance variation against hydrogen gas concentration is found to coincide with the power law. With this modification, a bell shaped was obtained which is in a closed agreement with the experimental result. In additions, the effect of silver, Ag and gold, Au modification of film in SnO2 gas sensor was also simulated. The simulated result in detecting 1-butanol gas shows that the optimum operating temperature was reduced by 150°C for both Ag/SnO2 and Au/SnO2 with higher sensitivity as compared to pure SnO2. Finally, the effect of pore radius, r and film thickness, L on the sensitivity was also simulated in detecting hydrogen gas. The simulated result for the pore radius shows that the sensitivity increases as pore radius increase at the fixed temperature, which is correlate with the Knudsen equation, Dk. For film thickness, the result shows that the sensitivity increases as the thickness of the film decreases due to a stronger contact between the target gas and the sensor's surface