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Understanding the High Photocatalytic Activity of (B, Ag)-Codoped TiO2 under Solar-Light Irradiation

Release time:2013-1-18      Source:admin      Reads:1502

              Ningdong FengQiang WangAnmin ZhengZhengfeng ZhangJie Fan

                                    Shang-Bin LiuJean-Paul Amoureux, and Feng Deng*


    The origin of the exceptionally high activity of (B, Ag)-codoped TiO2 catalysts under solar-light irradiation has been investigated by XPS and 11B solid-state NMR spectroscopy in conjunction with density functional theory (DFT) calculations. XPS experimental results demonstrated that a portion of the dopant Ag (Ag3+) ions were implanted into the crystalline lattice of (B, Ag)-codoped TiO2 and were in close proximity to the interstitial B (Bint.) sites, forming [Bint.–O–Ag] structural units. In situ XPS experiments were employed to follow the evolution of the chemical states of the B and Ag dopants during UV–vis irradiation. It was found that the [Bint.–O–Ag] units could trap the photoinduced electron to form a unique intermediate structure in the (B, Ag)-codoped TiO2 during the irradiation, which is responsible for the photoinduced shifts of the B 1s and Ag 3d peaks observed in the in situ XPS  spectra. Solid-state NMR experiments including 11B triple-quantum and double-quantum magic angle spinning (MAS) NMR revealed that up to six  different boron species were present in the catalysts and only the tricoordinated interstitial boron (T*) species was in close proximity to the  substitutional Ag species, leading to formation of [T*–O–Ag] structural units. Furthermore, as demonstrated by DFT calculations, the [T*–O–Ag]  structural units were responsible for trapping the photoinduced electrons, which prolongs the life of the photoinduced charge carriers and eventually  leads to a remarkable enhancement in the photocatalytic activity. All these unprecedented findings are expected to be crucial for understanding the  roles of B and Ag dopants and their synergistic effect in numerous titania-mediated photocatalytic reactions.