Synthesis of porous and visible-light absorbing Bi₂WO ₆/TiO₂ heterojunction films with improved photoelectrochemical and photocatalytic performances

This work reports the preparation of porous and visible-light absorbing Bi₂WO₆/TiO₂ heterojunction films as a photoelectrode and their photoelectrochemical and photocatalytic performances. The Bi₂WO₆ underlayers with high surface roughness were prepared by a superhydrophilicity-assisted method. The Bi₂WO ₆/TiO₂ bilayer films showed high interface area between the Bi₂WO₆ and TiO₂ layers. Significant enhancement in visible light photocurrent generation on the optimal Bi ₂WO₆/TiO₂ film was observed as compared with unmodified Bi₂WO₆ (a factor of 2) and unmodified TiO ₂ (a factor of 13) films. The optimal visible-light photocatalytic activity of the Bi₂WO₆/TiO₂ film was 15.1 nm of stearic acid degraded, which was 6 and 4.6 times higher than that of unmodified Bi₂WO₆ and TiO₂ films, respectively. The enhanced photoelectrochemical and photocatalytic performances of Bi ₂WO₆/TiO₂ films were attributed to the improved charge separation efficiency derived from the suitable valence band interaction between the two semiconductors, as well as high interface area and porous structure of the heterojunction bilayer films. Charge separation between Bi ₂WO₆ (underlayer) and TiO₂ (overlayer) was verified by photoluminescence (PL) and current-voltage (I-V) characteristics studies.