Co-precipitation synthesis,band modulation and improved visible-light-driven photocatalysis of Te4+/Ti4+-codoped Bi3Nb17O47

Bismuth niobate semiconductors are of considerable interest in both contaminant degradation and H₂-generation. However, the wide band gap strictly limits the optical absorption in visible-light wavelength. In this work, a new niobate semiconductor Bi₃Nb₁₇O₄₇ was prepared with co-precipitation synthesis. To modify the band structure, Te⁴⁺-, Ti⁴⁺-, and Te⁴⁺/Ti⁴⁺-doping were conducted in Bi₃Nb₁₇O₄₇ lattices. Rietveld refinements were used to investigate the crystal phase and structure. The UV–vis absorption measurements concluded that Te⁴⁺-, Ti⁴⁺- doping could greatly modify the band energy of Bi₃Nb₁₇O₄₇. The Te⁴⁺/Ti⁴⁺-doped sample could harvest more visible light in the longer-wavelength region being favorable for photocatalysis performances. This was verified by RhB photodegradation tests under the visible-light irradiation (λ > 420 nm). To discuss the photocatalytic mechanisms, XPS and impedance spectra were measured. The improved photocatalysis was related to the microstructure changes, charge carrier dynamics, oxygen vacancies, and redox couples of multivalent ions. The present work provides a valid route to modify the band structure and to improve the photocatalysis abilities via impurity ions Te⁴⁺/Ti⁴⁺-doping in bismuth niobate semiconductors.