Haili Lin

Visible light photocatalytic activity enhancement and mechanism of AgBr/Ag3PO4 hybrids for degradation of methyl orange

Novel AgBr/Ag(3)PO(4) hybrids were synthesized via an in situ anion-exchange method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light (λ>420 nm), AgBr/Ag(3)PO(4) degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure AgBr or Ag(3)PO(4). X-ray photoelectron spectroscopy (XPS) suggests that AgBr/Ag(3)PO(4) transformed to be Ag@AgBr/Ag(3)PO(4)@Ag system while remained good photocatalytic activity after 5 times of cycle experiments. In addition, the quenching effects of different scavengers proved that reactive OH and h(+) played the major role for the MO degradation. The photocatalytic activity enhancement of AgBr/Ag(3)PO(4) is closely related to the efficient separation of electron-hole pairs derived from the matching band potentials between AgBr and Ag(3)PO(4), as well as the good electron trapping role of Ag nanoparticles in situ formed on the surfaces of AgBr and Ag(3)PO(4) particles during the photocatalytic reaction.

In situ preparation of novel p-n junction photocatalyst BiOI/(BiO)2CO3 with enhanced visible light photocatalytic activity

Novel p-n junction photocatalysts BiOI/(BiO)2CO3 with different contents of BiOI were in situ synthesized by etching (BiO)2CO3 precursor with hydroiodic acid (HI) solution. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrometry (FT-IR), energy-dispersive spectroscopy (EDS) and UV-vis diffuse reflectance spectroscopy (DRS) were employed to study the structures, morphologies and optical properties of the as-prepared samples. Under visible light (λ>420 nm), BiOI/(BiO)2CO3 hybrid displayed much higher photocatalytic activity than pure (BiO)2CO3 and BiOI for the degradation of methyl orange (MO). The increased photocatalytic activity of BiOI/(BiO)2CO3 could be attributed to the formation of the p-n junction between p-BiOI and n-(BiO)2CO3, which effectively suppresses the recombination of photoinduced electron-hole pairs. Moreover, the tests of radical scavengers confirmed that •O2- and h+ were the main reactive species for the degradation of MO.

Photocatalytic activity of novel AgBr/WO3 composite photocatalyst under visible light irradiation for methyl orange degradation.

A novel AgBr/WO(3) composite photocatalyst was synthesized by loading AgBr on WO(3) substrate via deposition-precipitation method and characterized by XRD, SEM and DRS. The as-prepared AgBr/WO(3) was composed of monoclinic WO(3) substrate and face-centered cubic AgBr nanoparticles with crystalline sizes less than 56.8 nm. AgBr/WO(3) had absorption edge at about 470 nm in the visible light region. The optical AgBr content in AgBr/WO(3) was 0.30:1 (Ag/W) at the corresponding apparent rate, k(app), of 0.0160 min(-1) for MO degradation. The highest k(app) was 0.0216 min(-1) for 4 g/L catalyst. The OH acted as active species. Addition of H(2)O(2) within 0.020 mmol/L can efficiently trap electrons to generate more OH and further improved photocatalytic activity of AgBr/WO(3).

Novel I-BiOBr/BiPO4 heterostructure: synergetic effects of I− ion doping and the electron trapping role of wide-band-gap BiPO4 nanorods

A novel I−-doped BiOBr/BiPO4 (I-BiOBr/BiPO4) heterostructure was constructed by a facile deposition-precipitation method using wide-band-gap BiPO4 nanorods as the substrate. The as-prepared I-BiOBr/BiPO4 composite exhibited a notably enhanced photocatalytic performance in the decomposing of methyl orange and phenol under visible light (λ > 420 nm) irradiation in comparison with BiOBr, I-BiOBr, BiPO4 and BiOBr/BiPO4 reference samples. The photocatalytic activity improvement of I-BiOBr/BiPO4 mainly resulted from the synergetic effects of doped I− ions in I-BiOBr and the heterojunction interface between I-BiOBr and BiPO4. I− ions doping narrowed the band-gap energy of BiOBr to generate more photocharges under visible light irradiation. Moreover, BiPO4 quickly trapped and transferred the electrons originating from I-BiOBr. This study affords a facile strategy to intensively improve the visible light photocatalytic activity of the BiOX system for water contaminants removal.

Tunable photocatalytic and photoelectric properties of I−-doped BiOBr photocatalyst: dramatic pH effect

A series of I−-doped BiOBr (I-BiOBr) photocatalysts were prepared through adjusting the synthesis pH values of the reaction solution. The crystalline structure, light absorption, morphology and element component were measured by XRD, DRS, SEM, TEM, EDS, ICP-OES and XPS technologies. The doping of I− ions strongly broadened the visible light absorption range and improved the activity of I-BiOBr. More importantly, the photocatalytic activity of I-BiOBr dramatically depended on the synthesis pH values, in which I-BiOBr (0.5) displayed the best performance for removing methyl orange and phenol under visible light. The photoelectric property measurement revealed that I-BiOBr had stronger electron–hole separation efficiency than the corresponding BiOBr reference samples. With increase in the pH values, the I− ion doping contents varied a little but the surface charge state changed regularly. The decrease in the surface adsorbed negative Br− ions reduced the formation efficiency of active Br0 and resulted in low activity of I-BiOBr. This study provides a facile and efficient way to control the photocatalytic and photoelectric behaviors of novel I−-doped BiOX photocatalysts via changing the pH values of the reaction solution during synthesis.