Effect of Humidity on Characteristics of Hydrogen Sensors Based on Nanocrystalline SnO2 Thin Films with Various Catalysts

Abstract

The influence of humidity on the electrical and gas-sensitive characteristics of H2 sensors based on thin films SnO2 with deposited Pt/Pd disperse layers (Pt/Pd/SnO2:Sb) and with the additions of gold in the bulk and on the surface (Au/SnO2:Sb, Au) has been studied. The time dependences of the conductivity G(t) of sensors operating in pure air and in gas mixture containing hydrogen (air + H2) in thermo-cyclic operation modes were measured. It was shown that the conductance of films increases and the response to H2 decreases with an increase in the relative humidity from 10 to 70 %. In the sensors based on thin films Pt/Pd/SnO2:Sb exposed to hydrogen the over – barrier component of conductivity plays a decisive role. In case of the films modified by gold the channel component of conductivity is prevailing. The role deposited catalysts Pt/Pd and additives of gold in the process of adsorption of water molecules and hydrogen on the surface of tin dioxide is discussed.