Nanocomposites and nanomaterials

Pt-containing nanosized materials based on tin dioxide to create semiconductor hydrogen sensors

Matushko I.P., Oleksenko L.P., Maksymovych N.P., Fedorenko G.V., Lutsenko L.V., Arinarkhova H.O.

Chemical Department, Taras Shevchenko National University of Kyiv
12 Lva Tolstogo str., Kyiv 01033, Ukraine. 
E-mail: mipigor@gmail.com

Nowadays hydrogen is an ecological fuel and one of the most energy-intensive carriers. It is known that hydrogen is an explosive gas and that's why it is necessary to control its content in air during production, storage, transportation and usage of hydrogen. Development of highly sensitive sensors for hydrogen detection is an actual task for determination of H2 presence in air. Nanosized Pt/SnO2 based materials can be used for creation of gas sensitive layers of the adsorption-semiconductor sensors. It is known that increasing a ratio of the sensor material surface to the volume of the material can change its properties. Besides, it is known that platinum is a very active catalyst of H2 oxidation reaction. That is why the aim of the work was to obtain Pt/SnO2 nanomaterials and study their morphology, catalytic, structural and gas sensitive properties.
Nanosized material SnO2 was prepared by a sol-gel method. Introduction of the platinum additives to the nanomaterial was performed by impregnating it with H2PtCl6 solutions of different concentrations (0.21·10-2 - 35·10-2 M). The adsorption semiconductor sensors were made by thick film technology and their gas sensitive properties were studied. A ratio of the electrical resistance of the sensor in air (R0) to its electrical resistance in the analyzed gas with concentration of 40 ppm H2 in air (Rg) was chosen as a measure of the sensor response (γ = R0/Rg). 
It was shown by ТЕМ method that particle size of SnO2 nanomaterial ranged from 5 to 30 nm (an average particle size was 17 nm). The study by XRD method revealed that the structures of the samples correspond to a cassiterite phase.
The highest sensor response to H2 (γ=15,8) was achieved for the sensor obtained by impregnation of nanosized SnO2 with a solution of 15·10-2 M H2PtCl6 concentration at the sensor heater power consumption of 0.25 W. Study of the catalytic properties of the obtained Pt/SnO2 nanomaterials had shown that introduction of Pt increased their activities greatly and these catalytic properties in a great extent influence on the sensor response values. That is why catalytic reaction of hydrogen oxidation running on the sensor surface is crucial in the formation of the sensor response.