The design of semiconductor metal oxides (SMOs) with well-ordered porous structure has attracted tremendous attention owing to their larger specific surface area. Herein, three-dimensional inverse opal InO microspheres (3D-IO InO MSs) were fabricated through one-step ultrasonic spray pyrolysis (USP) which employed self-assembly sulfonated polystyrene (S-PS) spheres as a sacrificial template. The spherical pores observed in the 3D-IO InO MSs had diameters of about 4 and 80 nm. Subsequently, the catalytic palladium oxide nanoparticles (PdO NPs) were loaded on 3D-IO InO MSs via a simple impregnation method, and their gas sensing properties were investigated. In a comparison with pristine 3D-IO InO MSs, the 3D-IO PdO@InO MSs exhibited a 3.9 times higher response (R/R = 50.9) to 100 ppm acetone at 250 °C and a good acetone selectivity. The detection limit for acetone could extend down to ppb level. Furthermore, the 3D-IO PdO@InO MSs-based sensor also possess good long-term stability. The extraordinary sensing performance can be attributed to the novel 3D periodic porous structure, highly three-dimensional interconnection, larger specific surface area, size-tunable (meso- and macroscale) bimodal pores, and PdO NP catalysts.

Abstract:In this study, the electrical characteristics and surface reactions of three different kinds of In2O3 based gas sensors were investigated under CO exposure in dry and humid air by using DC electrical resistance measurements and Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). For the first time one gains insight into the surface reactions during the exposure to CO and humidity. The sensors show different behavior on the baseline in humidity depending on the material which is due to different kinds of OH-groups. The resistance change under CO and humidity exposure are additive and the molecules compete for the same reaction partner confirmed by the spectroscopy results. Through isotopic exchange experiments, different adsorbates could be identified.

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