Effects of Lanthanum/Gadolinium Doping on Crystal Structures, Electronic Properties and Optical Characteristics of Bismuth Tungstate Photocatalyst: DFT Approach

First principles calculations are employed to evaluate the crystal structures, electronic properties, optical properties and carrier effective masses of pure and Lanthanum (La) or Gadolinium (Gd) doped bismuth tungstate (Bi2WO6). The calculated results reveal that La or Gd dopants do not modify the host crystalline structure. The reduction of the band gap energy of doped structures suggests that La- or Gd-doped Bi2WO6 materials are capable to harvest more visible light in solar energy. Moreover, it is found that the absorption edges show a red shift with the loading of La or Gd atoms, in agreement with the experimental observations in the literature. The mechanism of enhanced photocatalytic performance for the doped materials could be attributed to the high ratio of the effective mass of holes to that of electrons or, equivalently the lower recombination rate of the charge carriers.