Microwave-assisted growth of In2O3 nanoparticles on WO3 nanoplates to improve H2S-sensing performance

Abstract

Hierarchical In₂O₃@WO₃ nanocomposites, consisting of discrete In₂O₃ nanoparticles (NPs) on single-crystal WO₃ nanoplates, were synthesized via a novel microwave-assisted growth of In₂O₃ NPs on the surfaces of WO₃ nanoplates that were derived through an intercalation and topochemical-conversion route. The techniques of XRD, SEM, TEM and XPS were used to characterize the samples obtained. The gas-sensing properties of In₂O₃@WO₃ nanocomposites, together with WO₃ nanoplates and In₂O₃ nanoparticles, were comparatively investigated using inorganic gases and organic vapors as the target substances, with an emphasis on H₂S-sensing performance under low concentrations (0.5–10 ppm) at 100–250 °C. The results show that the In₂O₃ NPs with a size range of 12–20 nm are uniformly anchored on the surfaces of the WO₃ nanoplates. The amounts of the In₂O₃ NPs can be controlled by changing the In³⁺ concentrations in their growth precursors. The In₂O₃@WO₃ (In/W = 0.8) sample has highest H₂S-sensing performance operating at 150 °C; its response to 10 ppm H₂S is as high as 143, 4 times higher than that of WO₃ nanoplates and 13 times that of In₂O₃ nanocrystals. However, the responses of the In₂O₃@WO₃ sensors are less than 13 upon exposure to 100 ppm of CO, SO₂, H₂, CH₄ and organic vapors, operating at 100–150 °C. The improvement in response and selectivity of the In₂O₃@WO₃ sensors upon exposure to H₂S molecules can be attributed to the synergistic effect of In₂O₃ NPs and WO₃ nanoplates, hierarchical microstructures and multifunctional interfaces.