Synthesis and characterization of Sm³⁺-doped Y(OH)₃ and Y₂O₃ nanowires and their NO reduction activity

A highly crystallized hexagonal structure with large aspect-ratios, almost uniform diameter and length of several tens of microns of Y(OH)₃ nanowires, have been successfully synthesized by controlling the hydrothermal reaction time as well as an addition of 5 mol% Sm³⁺ at 180 °C for 24 h under N₂ atmosphere. The hydrothermal products of yttrium nitrate precursor alone have showed merely nanosheets like structure under the same reaction conditions. The microstructures of the Y(OH)₃ nanowires were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution (HR)TEM and selected area electron diffraction (SAED). After heat treatment, the as-prepared Y(OH)₃ could be completely transformed into Y₂O₃ while maintaining the nanowires structure up to the temperature at 400 °C in air. The Y₂O₃:Sm³⁺ have been tested for the reduction of NO under an oxidizing atmosphere with hydrocarbons. Moreover, the NO reduction activity under atmosphere containing water vapor was also investigated.