Enhanced photocatalytic activity of Gd3+ doped TiO2 and Gd2O3 modified TiO2 prepared via ball milling method

Abstract

Gd3+/TiO2 and Gd2O3/TiO2 nanoparticles were prepared by ball milling method. The effects of Gd3+ ion and Gd2O3 on the structure and optical property of TiO2 were studied by XRD and UV-vis DRS. Specific surface area was determined by Brunauer-Emmett-Teller (BET) method. The morphology and elemental composition were characterized by SEM-EDS. XPS was used to determine the surface compositions and chemical character of elements. The sample sizes and microstructures were observed by TEM. The photocatalytic activities of TiO2 nanoparticles modified with rare earth metal gadolinium (Gd3+ ion or Gd2O3) were evaluated by degradation of methylene blue (MB) under UV light. Experimental results indicate that 2.5 mol% Gd3+/TiO2 shows the best photocatalytic activity compared with Gd2O3/TiO2 and pure TiO2. The existence of gadolinium can exhibit the aggregation and induce lattice distortion of TiO2 obtained from XRD, SEM and TEM results. The band gap energy of 2.5 mol% Gd3+/TiO2 decreases to 3.07 eV and it leads to visible light absorption response which can be seen from UV-vis absorption spectra. The surface area of 2.5 mol% Gd3+/TiO2 equals to 85.8 m2/g and average crystal size is 21.1 nm. EDS and XPS analyses reveal that gadolinium can be introduced either into TiO2 lattice or adsorbed on the surface of TiO2. The content of surface OH groups in 2.5 mol% Gd3+/TiO2 is 50.88% (1.55 times higher than that of pure TiO2) and the content of lattice oxygen decreases to 11.26%. The MB (25 mg/L) degradation reaction rate constants of 2.5 mol% Gd3+/TiO2, 0.5 mol% Gd2O3/TiO2 and pure TiO2 were 0.0713, 0.0588 and 0.0263 min−1, respectively. The degradation rates of rhodamine B (30 mg/L) in 60 min are 97.9%, 90.1% and 84.6% for 2.5 mol% Gd3+/TiO2, 0.5 mol% Gd2O3/TiO2 and pure TiO2, respectively.