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

Abstract Gd 3+ /TiO 2 and Gd 2 O 3 /TiO 2 nanoparticles were prepared by ball milling method. The effects of Gd 3+ ion and Gd 2 O 3 on the structure and optical property of TiO 2 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 TiO 2 nanoparticles modified with rare earth metal gadolinium (Gd 3+ ion or Gd 2 O 3 ) were evaluated by degradation of methylene blue (MB) under UV light. Experimental results indicate that 2.5 mol% Gd 3+ /TiO 2 shows the best photocatalytic activity compared with Gd 2 O 3 /TiO 2 and pure TiO 2 . The existence of gadolinium can exhibit the aggregation and induce lattice distortion of TiO 2 obtained from XRD, SEM and TEM results. The band gap energy of 2.5 mol% Gd 3+ /TiO 2 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% Gd 3+ /TiO 2 equals to 85.8 m 2 /g and average crystal size is 21.1 nm. EDS and XPS analyses reveal that gadolinium can be introduced either into TiO 2 lattice or adsorbed on the surface of TiO 2 . The content of surface OH groups in 2.5 mol% Gd 3+ /TiO 2 is 50.88% (1.55 times higher than that of pure TiO 2 ) and the content of lattice oxygen decreases to 11.26%. The MB (25 mg/L) degradation reaction rate constants of 2.5 mol% Gd 3+ /TiO 2 , 0.5 mol% Gd 2 O 3 /TiO 2 and pure TiO 2 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% Gd 3+ /TiO 2 , 0.5 mol% Gd 2 O 3 /TiO 2 and pure TiO 2 , respectively.