Fabrication of bidirectionally doped β-Bi2O3/TiO2-NTs with enhanced photocatalysis under visible light irradiation

Abstract Stable β-Bi 2 O 3 /TiO 2 -NTs photocatalyst with excellent visible-light-activity is successfully prepared by bidirectional doping. Stake structure of the TiO 2 -NTs provides a larger specific surface area and makes the contact area between the TiO 2 -NTs and β-Bi 2 O 3 much larger; The stake structure of TiO 2 -NTs not only leads to a firmer combination of TiO 2 -NTs and β-Bi 2 O 3 , but also makes them dope one another deeply. The modification of Bi species into TiO 2 -NTs can form Bi-O-Ti chemical absorption bonds, then a localized impurity level is generated within the band gap. Electrons can be excited and transferred from the Bi 3+ impurity level to the conduction band (CB) of TiO 2 , similar to narrowing the band-gap of TiO 2 -NTs, resulting in a red shift of the absorption edge and an enhancement in visible-light activity. During annealing, Bi atoms are partially replaced by Ti atoms. The lattice of β-Bi 2 O 3 is compressed around the Ti impurity, making the lattice dislocate and distort. This dislocation and distortion leads to an increase in the β-Bi 2 O 3 valance band (VB), from 2.02 to 2.28 eV. Accordingly, the weak oxidability of β-Bi 2 O 3 is improved, and its photocatalytic ability is further enhanced. Moreover, this lattice dislocation and distortion changes the Bi-O distances, thus remarkably improving the stability of the β-Bi 2 O 3 /TiO 2 -NTs.