Room-temperature hydrogen sensing properties of SnO2 -coated multi-walled carbon nanotubes

A SnCl2 solution was used to prepare SnO2-coated multi-walled carbon nanotubes (SnO2/MWCNTs), and their hydrogen sensing properties at room temperature was studied. SEM and TEM observations indicate that SnO2 nanoparticles with a size of 5 nm are uniformly coated on the MWCNTs, forming a continuous SnO2 coating. The SnO2/MWCNTs are sensitive to 10(-4) hydrogen at room temperature. During the sensing measurement at room temperature for 10(-3) hydrogen mixed with argon gas, the current change with gas concentration is reversed after the mixed gas is switched to air. This can be ascribed to the reaction between O-2 in air and residual H-2 around the SnO2/MWCNTs to form adsorbed H2O and the subsequent desorption of H2O by substitution adsorption of O-2 in air. The H2O adsorption may lead to a decrease of the electric resistance of SnO2/MWCNTs and thus an increase of current measured. The reversal of current implies that the SnO2/MWCNTs may possess a good sensitivity to humidity at room temperature.