In situ formation of Au/SnO2 nanocrystals on WO3 nanoplates as excellent gas-sensing materials for H2S detection

•Au/SnO2@WO3 composites were formed by reducing HAuCl4 with SnCl2 on WO3 nanoplates.•Au/SnO2@plate-WO3 is high sensitive to H2S detection at low temperature of ∼50 °C.•Au/SnO2@plate-WO3 is highly selective to H2S detection in various gases or vapors.•Synergistic effect of Au/SnO2 and WO3 results in enhancement in H2S-sensing property.

In order to improve the gas-sensing performance at low temperature, binary Au/SnO2 species were used to modify WO3 nanoplates, i.e., Au/SnO2@plate-WO3 composites, which were synthesized by in-situ reducing HAuCl4 with SnCl2 adsorbed on the surfaces of WO3 nanoplates derived via an intercalation and topochemical conversion route. XRD, XPS, SEM, TEM and UV–vis DR spectra were used to characterize the samples. The gas-sensing properties of the samples were evaluated using H2S as target gas. The Au/SnO2 nanoparticles with small sizes (several nanometers) are uniformly anchored on the surfaces of WO3 nanoplates. The response of the 0.5%Au/SnO2@plate-WO3 sensor to 10 ppm H2S is up to 220 at 50 °C, 28 times higher than that of the plate-WO3 sensor. The optimal operation temperature of the plate-WO3 and Au/SnO2@plate-WO3 sensor for H2S detection is about 150 °C. The responses of the Au/SnO2@plate-WO3 sensor to 100 ppm of CO, SO2, H2, CH4 and organic vapors are negligibly low (1.2–8.0) at low temperatures. The possible explanation for the high selectivity and response in H2S detection at low temperatures can be the synergistic effect of the binary Au/SnO2 nanoparticles and ultra-thin WO3 nanoplates in adsorption, reaction and diffusion of the gas molecules.

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