Hydrogen sensor based on MWNTs/WO3

In this article we report hydrogen sensing property of WO₃/MWNTs thin films that were fabricated by spin-coating on alumina substrates. The MWNTs were initially functionalized (f-MWNTs) to enhance dispersion in the sol of multiwalled carbon nanotubes (MWNTs) and tungsten trioxide (WO₃). Microstructure, morphology and chemical composition of the materials were characterized by SEM, TEM, XRD and XPS methods. Our results show WO₃ nanoparticles were nucleated on oxygenated group on surface of f-MWNTs in hybrid suspension. After annealing the films at 350 °C, electrical conductance measurements at different operating temperature were performed and the results indicates rather fast and linear sensitivity as a function of hydrogen concentrations (0.0024% to 1.14%). The gas sensitivity are suggested to arise mainly from the increase in surface area as well as development of two types of depletion layers, one at the n-WO₃/ p-MWNTs hetero junction and the other at WO₃ grain boundaries.