Rare earth induced lattice distortion of Bi2WO6 to effectively improve photocatalytic performance: Experimental and DFT calculations

• Published in: Optical materials Vol. 155; p. 115798
• Main Authors: Liu, Morigejile, Bao, Morigen, Cao, Hongzhang, Yu, Xiaoli, Zhao, Si Qin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2024
• Subjects: Bi2WO6; DFT calculation; Lattice distortion; Photocatalytic performance; Rare earth; DFT calculation; Rare earth; Lattice distortion; Bi2WO6; Photocatalytic performance
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2024.115798

The excellent visible light photocatalytic activity of bismuth-based photocatalysts has attracted the interest of many scholars at home and abroad. In this paper, rare earth (Sm, La, Ce, Eu) doped Bi2WO6 photocatalysts were prepared by a one-step hydrothermal method using bismuth nitrate and sodium tungstate as precursors. The microstructures and spectroscopic performances of prepared materials were investigated utilizing characterization methods, such as XRD, XPS, UV–vis, TEM, and N2 adsorption-desorption, etc., and the effluent removal performances were studied by using rhodamine B as a simulated degradation dye and the photodegradation mechanism was investigated in combination with DFT calculations. XRD indicates that the rare earth doping leads to the lattice distortion of the (131) crystal surface of Bi2WO6, and the relative amount of distortion is directly proportional to the photocatalytic activity; UV–vis spectra show that the absorption edge of Bi2WO6 is obviously red-shifted with the rare earth doping, and N2 adsorption-desorption curve show that the doped rare earths make the specific surface area of the sample effectively increased. Moreover, XPS spectrum suggests that the doped rare earth Ce and Eu often exist in the form of metastable oxidation states, and the transformation between Ce3+/Ce4+ and Eu2+/Eu3+ oxidation states is easy to form impurity energy levels between Bi2WO6, which make the energy level significantly enriched to broaden the absorption range and reduce band gap width of the material. DFT calculations further indicate that the rare earths successfully replace Bi sites. One of the main reasons for the improvement of photocatalytic activity is that rare earth doping is easier to replace Bi sites, leading to increased relative aberration; another one is that the arrangement of EVB and ECB in the photocatalytic mechanism is type-II, which contributes to red-shift of absorption edge and effective separation of electron-hole pairs in the photocatalytic process, thus improving the photocatalytic activity. •The doping of rare earths causes the light absorption edge of Bi2WO6 to be red-shifted, resulting in the forbidden bandwidth becoming narrower and more visible light can be absorbed, to produce more photogenerated electron-hole pairs.•The rare earths Ce and Eu can effectively release electron acceptors to capture photogenerated electrons from the valence band to the conduction band and promote the effective separation of photogenerated electrons and holes.•After doping rare earth, the lattice distortion of Bi2WO6 leads to smaller grain size and larger specific surface area, which helps the rapid migration of photogenerated electron-hole pairs to the surface to participate in the photocatalytic reaction.•DFT calculations show that doped rare earths are prone to form spatial structural defects, thereby increasing the specific surface area and further improving the photocatalytic performance.