Pd–WO3/reduced graphene oxide hierarchical nanostructures as efficient hydrogen gas sensors

Abstract

Pd–WO3 nanostructures were incorporated on graphene oxide (GO) and partially reduced graphene oxide (PRGO) sheets using a controlled hydrothermal process to fabricate effective hydrogen gas sensors. Pd–WO3 nanostructures showed ribbon-like morphologies and Pd–WO3/GO presented an irregular nanostructured form, while Pd–WO3/PRGO exhibited a hierarchical nanostructure with a high surface area. Gas sensing properties of thin films of these materials were studied for different hydrogen concentrations (from 20 to 10,000 ppm) at various temperatures (from room temperature to 250 °C). Although adding GO in the Pd–WO3, after hydrothermal process could increase the film conductivity, gas sensitivity was reduced to half, due to lower surface area of the irregular morphology in comparison with the ribbon-like morphology. The Pd–WO3/PRGO films showed an optimum sensitivity (∼10 folds better than the sensitivity of Pd–WO3/GO), and a fast response and recovery time (<1 min) at low temperature of 100 °C. Moreover, the Pd–WO3/PRGO-based gas sensor was sensitive to 20 ppm concentration of hydrogen gas at room temperature. The results confirmed the effect of residual oxygen-containing functional groups of PRGO on the growth and morphology of Pd–WO3 as well as gas sensing properties of metal oxide/graphene based hybrid nanostructures.