Synthesis of NiTiO₃-Bi₂MoO₆ core-shell fiber-shaped heterojunctions as efficient and easily recyclable photocatalysts

Development of efficient and recyclable photocatalysts has drawn more and more attention. Herein, we have prepared a kind of core-shell fiber-shaped NiTiO₃-Bi₂MoO₆ heterojunction as an efficient and easily recyclable visible-light-driven photocatalyst. NiTiO₃ nanofibers have been obtained by an electrospinning-calcination method; and in situ growth of Bi₂MoO₆ is conducted on the surface of NiTiO₃ by a simple solvothermal method. NiTiO₃-Bi₂MoO₆ heterojunctions are composed of NiTiO₃ nanofibers with a diameter of about 150 nm whose surfaces are decorated by Bi₂MoO₆ nanoneedles with a diameter of ∼8 nm and length of ∼35 nm. Under visible light irradiation, NiTiO₃-Bi₂MoO₆ heterojunctions exhibit significantly high photocatalytic activities compared with NiTiO₃, Bi₂MoO₆ and a mechanical mixture (22 wt% NiTiO₃ + 78 wt% Bi₂MoO₆) when rhodamine B (RhB) or 4-chlorophenol (4-CP) are selected as model pollutants. For example, NiTiO₃-Bi₂MoO₆ heterojunctions achieve the highest photodegradation efficiency of RhB (97.2%) compared to 21.9% by NiTiO₃, 40.3% by Bi₂MoO₆ and 45.0% by the mechanical mixture. The enhanced photocatalytic activities can be mainly attributed to the efficient separation of photogenerated electron-hole pairs. During the photocatalytic degradation of RhB, superoxide radical ions (O₂^-) and photogenerated holes (h⁺) are detected as the main active species. Moreover, NiTiO₃-Bi₂MoO₆ heterojunctions can be recycled by sedimentation and still possess excellent stability. Therefore, NiTiO₃-Bi₂MoO₆ heterojunctions have great potential to act as efficient and recyclable photocatalysts in practical applications of environmental purification.