Surfactant-free hydrothermal synthesis and sensitivity characterization of Pd-doped SnO2nanocrystals on multiwalled carbon nanotubes

In the present study, a simple approach has been presented to in situ deposition of Pd-doped well-crystallized SnO2nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution of SnCl2. The morphology, microstructure and surface chemistry of the as-prepared nanocomposites were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HRTEM and XRD results show that the well-crystallized SnO2nanocrystals with uniform crystal size (about 5 nm) tightly and homogenously coat on the entire surface of the MWCNTs. The carboxylic function groups on the MWCNTs surface may supply nucleation sites for facilitating the in situ deposition of SnO2nanocrystals. The XPS results reveal that the chemical states of the nanocomposites and the dopant of Pd mainly exists in two chemical states as Pd2+and Pd4+. The response of the 2.5 at% Pd-doped SnO2/MWCNTs nanocomposites to 1000 ppm NO at the temperature of 250 °C behaviors better, whose response time is about 70 s and the sensitivity is about 4.62.