Enhancing the Photocatalytic Performance of BaSn-based Composites by Doping Rare Metals

Abstract

Rare metal (La or Nd) doped BaSn-based composites with highly polycrystalline nature were successfully synthesized through a simple hydrothermal route. The doped composites were investigated by X-ray diffraction, electron microscopy, solid ultraviolet diffuse reflectance spectrum, X-ray photoelectron spectroscopy, photoluminescence, electrochemical impedance spectroscopy, and photocatalytic measurements. La and Nd doping induces the morphological change of the BaSn-based composites from the nanorods to irregular nanoscale particles with the average size of about 100 nm. La and Nd in the doped composites exist in the form of cubic La₂Sn₂O₇ and cubic Nd₂Sn₂O₇ phases. The absorption edge of the doped composites red-shifts comparing with that of the non-doped composites. The doped BaSn-based composites with the La or Nd mass ratio of 8 wt% possess the smallest band-gap energy in the doped composites and the good light absorption ability. The La or Nd doping mass ratio has an important role in the photocatalytic degradation of the crystal violet (CV) dye. The CV molecules in the 20-mL CV solution with 10 mg L⁻¹ can be totally removed by the 20-mg La- or Nd-doped BaSn-based composites under the light irradiation for 150 min. Scavenger experiments show that hydroxyl free radicals (·OH) and superoxide anion radicals (·O₂⁻) are effective oxidizing agents for CV degradation. Photoluminescence and electrochemical impedance spectroscopy show that the significant decrease in the recombination ability of the electron and hole pairs by the rare metal doping is of great importance for enhancing the photocatalytic activity of the BaSn-based composites. The La- or Nd-doped BaSn-based composites show good reusability for CV degradation.