Influence of synthesis conditions on physico-chemical and photocatalytic properties of rare earth (Ho, Nd and Sm) oxides

Three different rare earth metal (samarium, neodymium and holmium) oxides were synthesized by adapting organic and inorganic routes. The influence of synthesis route over the physico-chemical characteristics of the rare earth metal oxides was studied using X-ray diffraction, FT-IR, thermogravimetric analysis, microscopy (FESEM and HRTEM), N2-physisorption and diffusive reflective ultraviolet-visible spectroscopy techniques. The XRD, electron microscopy and N2-physisorption results indicated that the samples synthesized by organic route possessed smaller crystallite/particle size and high surface area with macro size pores compared to the samples synthesized by inorganic route. The synthesis conditions also influenced the morphology of the samples. The samples synthesized by organic route possessed sheets like morphology with large spaces in between the sheets, in contrast highly agglomerated particles were observed in case of samples synthesized by inorganic route. All the synthesized rare earth oxides were utilized as photocatalysts for degradation of crystal violet dye under visible light irradiation. The samples synthesized by organic route exhibited high photocatalytic efficiencies. Samarium oxide synthesized using organic route offered the superior photocatalytic performance as this sample possessed low band gap energy, high surface area, pore volume and presence of surface reactive −OH groups. In addition, the synthesized rare earth metal oxide catalysts exhibited excellent recyclability for photocatalytic crystal violet degradation. Keywords: Rare earth metal oxide, Organic route, Inorganic route, Structural properties, Photocatalytic activity