Among tremendous efforts for enhanced photocatalysis, construction of heterojunction has been deemed as an effective means. In comparison with type II heterojunction, type I heterojunction receives less attention due to accumulation and increased recombination of charge carriers in one side of heterojunction. Herein, we take NaBi(MoO4)2/Bi2MoO6 as an example of type I heterojunction and explore means to improve the photocatalytic performance of NaBi(MoO4)2/Bi2MoO6 heterojunction. We employ TiO2 electrospun nanofibers as substrates and separately grow NaBi(MoO4)2 and Bi2MoO6 nanostructures on the skeleton of TiO2. The characterization results show that TiO2 changes type I heterojunction into multiheterojunction integrating two type II heterojunctions. Photocatalytic tests demonstrate that as-constructed multi-heterojunction is of higher activity than that of single type I or II heterojunction, respectively, where photogenerated electrons are accumulated on the surface of TiO2 and photogenerated holes are accumulated on NaBi(MoO4)2 and Bi2MoO6, respectively. This study highlights the potential application of TiO2 electrospun nanofibers in the construction of multiheterojunction for enhanced visible light photocatalysis.

The double heterojunction of Pr2Sn2O7@Bi2Sn2O7/TiO2 composite was prepared by one-step hydrothermal method using TiO2 electrospun nanofibers as substrate. The structures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet (UV)-visible diffuse reflectance spectroscopy and photoluminescence. The performance of photocatalytic hydrogen production over the composite catalyst was studied under UV-visible light. The Pr2Sn2O7@Bi2Sn2O7/TiO2 composite nanofibers showed high photocatalytic activity for hydrogen production. The hydrogen production rate reached 587.1 mu mol h(-1) g(-1), which was 2.7 and 7.1 times that of Bi2Sn2O7/TiO2 and TiO2, respectively. The main reasons for the high photocatalytic activity included broadened spectral range, 4f-4f transition from Pr3+ of Pr2Sn2O7 and increased separation of the photogenerated carriers by double hetemjunction via direct Z-scheme transfer.

Gd and N co-doped SrTiO3/TiO2 composite nanofibers were prepared via one step hydrothermal synthesis growth of SrTiO3 nanostructures using electrospun anatase TiO2 nanofibers as both substance and reactant. The phase composition, microstructure, morphology and optical properties of the sample were characterized by X-ray diffraction (XRD), scanning electron mictoscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence spectroscopy (PL). The results indicated that the heterostructure formed by SrTiO3 and Tio(2), plays an important role in the suppression of electron-hole recombination and improves the photocatalytic performance of TiO2 nanofibers. The excellent visible light photocatalytic activity of this substance may be due to the generation of a new band gap that enables the catalyst to absorb visible light and results in the lattice defects which acts as a recombination center of photoinduced electrons and holes. The synergistic effect of Gd-N co-doping and heterojunction could effectively improve the visible-light photocatalytic activity of SrTiO3/TiO2 composite nanofibers.

The plasma Bi/Bi2MoO6/TiO2 composite nanofibers were prepared via a facile one-step solvothermal method, using electrospun TiO2 nanofibers as substrate, and glucose as reducing agent. The photocatalytic activity of the samples were evaluated by photodegradation of rhodamine B and 4-chlorophenol solution under visible light irradiation. The results showed that metal Bi nanoparticles were generated on the surface of Bi(2)MoO(6 )nanosheets via reduction of Bi3+ in situ by glucose, meanwhile grew on the TiO2 nanofibers surface. The photocatalytic activity of the Bi/Bi2MoO6/TiO2 composites nanofibers can be further improved by depositing metallic Bi owing to its surface plasmon resonance. The RhB catalyzed by the sample was degraded by 95.8% under visible light irradiation for 50 min, and the degradation efficiency remained over 92% after 5 cycles while the 4-CP was degraded for 68.8% under visible light irradiation for 180 min. All above results suggest that the photocatalysts have good photocatalytic activity and stability.