Telegieieva O. Catalytic oxidation of methane and hydrogen on semiconductor materials base on SnO2, modified with Pt or Pd, and sensitivity of corresponding sensors

The dissertation is devoted to determination of regularities of the methane and hydrogen oxidation, which are proceeded on the semiconductor sensor materials based on SnO2, modified with platinum metal (in the wide interval of Pt or Pd concentration), to examination of the effect of bimetallic systems Pt-Pd admixture on the catalytic activity of the sensor materials, and also to study the sensitivity of corresponding sensor to СН4 and Н2. It is shown, that obtained sensor materials with Pt(Pd) admixture possesses high catalytic activity in the methane and hydrogen oxidation, and the activity of sensors increases with increase of the supported metal amount. It is shown, that the catalytic activity of supported Pt-Pd systems is higher, than that of these pure metals, i.e. combined effect of Pt and Pd, and the phenomenon of synergism are observed. The optimum composition of bimetallic admixture Pt-Pd is determined. It is shown, that the most active catalysts of the methane and the hydrogen oxidations aresamples with ratio Pd:Pt = 2:1 and Pd:Pt = 1:2, respectively. The kinetics and the reactions mechanism were studied. It is shown, that experimental data corresponds to the Eley-Riedel mechanism for the methane and hydrogen oxidation. The kinetic equations describing all the data obtained are proposed. The sensitivity of the sensor materials based on SnO2 with admixtures of Pt(Pd) to СН4 and Н2 was studied. It was shown that the sensors sensitivity passes through a maximum with increase of platinum metal amount. The symbasis in the dependences of the sensor materials catalytic activity and sensitivity with increasing of Pt(Pd) admixture content is determined for small concentrations of the metals.It is shown, that physical-chemical regularities of the mechanism of the gases interaction with the gas-sensitive materials surface form the basis for creation of high sensitive adsorptive-semiconductor sensors.