Toluene sensing properties of porous Pd-loaded flower-like SnO2 microspheres

Pd-loaded flower-like SnO2 microspheres were synthesized by a solvothermal method. Various concentrations of Pd dopant (0 mol%, 0.5 mol%, 1.2 mol%, 2 mol% and 2.3 mol%) were added into precursors. The structure of SnO2 was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The actual atomic ratios of Pd-to-Sn (as deduced from XPS data) are the same as the ratios of raw materials. And the O 1s binding energy of 1.2 mol% Pd–SnO2 is the lowest in all tested samples. The SEM images show a flower-like microspheres composed of tiny nanoparticles structure of the materials. The sensors made of the Pd-loaded SnO2 were tested at different operating temperatures to various gases. The sensors fabricated using 1.2 mol% Pd-loaded SnO2 exhibited good toluene sensing properties at operating temperature 250 °C, and the minimum-detection-limit was down to 0.08 ppm. The sensor also exhibited better sensing characteristics for toluene as compared to other possible interference gases such as benzene, acetone, formaldehyde, ammonia. The sensing mechanisms of Pd-loaded SnO2 to toluene were discussed.