Mechanism Study of ZnO Nanorod-Bundle Sensors for H₂S Gas Sensing

This work reports the H2S gas-sensing properties of ZnO nanorod bundles and an investigation of their gas sensing mechanism. A one-dimensional ZnO nanostructure was synthesized using the hydrothermal method; scanning electron microscopy (SEM); and X-ray diffraction (XRD) spectra confirmed that the structures were crystalline ZnO of hexagonal structure. A furnace-type gas sensing system was used to characterize the nanorod bundles’ sensing properties in air containing dilute H2S gas (50 ppm) at sensing temperatures Ts ≤ 500 °C. The response of ZnO nanorod-bundle sensors to H2S gas increased with Ts; this trend may be due to chemical reaction of nanorods with gas molecules. X-ray photoelectron spectroscopy results indicated that the sensing mechanism of the ZnO nanorod-bundle sensor was explained by both the well-known surface reaction between H2S and adsorbed oxygen on ZnO, and the formation of zinc−sulfur bonding in ZnO nanorods, which becomes a dominant sensing mechanism at high Ts above 300 °C.