A study on Gas sensing Properties and Reaction Mechanism of Au@SnO2 Core-shell Structure Nanoparticles to H2S Gas

Abstract

The H2S is a toxic and malodorous gas produced from coal mine, natural gas manufacturing processes, and wastewater treatment plants. Due to increased environmental concern, there is an increasing demand for semiconductor gas sensors that are selective and responsive towards H2S gas.SnO2 has been known as a representative semiconductor gas sensing material because of chemical stability and high electron mobility. However SnO2 has a problem that H2S gas doesn’t detached after adsorbing on the surface on SnO2. To solve this problem, the use of noble metal catalysts has been suggested. Au nanoparticles (NPs) are reported to be a good catalyst for the H2S oxidation reaction. To investigate the effects of Au NPs on H2S adsorption and desorption, Au@SnO2 core-shell NPs were applied as a sensing material.In this study, Au@SnO2 core-shell NPs has been synthesized by microwave-assisted hydrothermal method. Au@SnO2 core-shell NPs were calcined at various temperatures (350°C ~ 550°C) to control the surface morphology and crystallinity of SnO2 shell, and their gas sensing property were investigated towards H2S gas (2 ppm to 100 ppm). Based on the results of the sensing test of Au@SnO2 core-shell NPs, we examined the effect of Au NPs on H2S adsorption and desorption.The Au@SnO2 core-shell structure NPs were successfully synthesized by microwave-assisted hydrothermal method, and the particle size was 26-30 nm and the shell thickness of SnO2 shell layer was 14-18 nm. The highest sensing responses of pure SnO2 and Au@SnO2 core-shell NPs showed at the working temperature of 200°C, the responses value to 100 ppm H2S gas were 4,748 and 517, respectively. The optimum working temperature for Au@SnO2 core-shell NPs for detecting H2S gas was at 300°C because the gas sensing response showed relatively high as compared to pure SnO2 and the recovery rate was the highest value. Moreover, the selectivity of H2S toward CO, CH4, C2H5OH gases appeared at this working temperature. The reason why Au@SnO2 core-shell NPs selectively reacted with H2S gas at 300°C was due to the catalytic activity of Au core for H2S oxidation reaction.Keywords: Au@SnO2, nanoparticle, semiconductor gas sensor, H2S gas, adsorption