Organic/Inorganic Core-Shell Structure Photocatalyst Syntheses And Study On Relationship Of Structure-Property

In this paper,a series of organic/inorganic core-shell photocatalyst with controlled ultrathin g-C₃N₄ shell were prepared through different methods,so as to profoundly reveal the relationship between core-shell structure and photocatalytic activity.The reaction system from strong oxidizing acids to a neutral hydrothermal reaction system were developed.The core-shell structure photocatalyst including g-C₃N₄@TiO₂ with a single oxide as core and g-C₃N₄@Bi₂WO₆,g-C₃N₄@BiPO₄ with complex oxide as core have been successfully prepared.The electron transfer on the interface of core-shell was regulated by controlling the thickness of the g-C₃N₄ shell,which could effectively regulate the photocatalytic activity.The mechanism of the enhancement activity of core-shell structure photocatalyst was also explored.The g-C₃N₄@TiO₂ core-shell structure photocatalysts with controlled ultrathin g-C₃N₄ layer（0 nm,1.0 nm,1.5 nm,3.0 nm）were prepared by a new method of the sol-gel approaches in situ coating re-assembled.The electronstatic potential difference of the interface increases dramatically with the thickness of g-C₃N₄ shell layers increasing.While with the thickness of g-C₃N₄ further increase the electronstatic potential difference has not increase,which is scrutinized by DFT calculations.The trend of electronstatic potential difference with g-C₃N₄ layers is consistent with the law between different thickness of g-C₃N₄ shell layer and the corresponding catalytic activity.A new catalytic concept namely layer-dependent effect was found,that is number of layers over g-C₃N₄ of the core-shell structure determines photocatalytic activity.The g-C₃N₄@TiO₂ sample with 1.0 nm thickness of shell layers has the highest visible light photocatalytic degradation phenol activity which is almost 7.2 times as high as that of bulk g-C₃N₄.The g-C₃N₄ bulk phase material was cut into CN transparent precursor by the process of neutral hydrothermal reaction using water as solvent and then in situ coating low temperature catalytic polymerization to fabricate ultrathin nanosheet g-C₃N₄@Bi₂WO₆ core-shell structure photocatalyst with controlled g-C₃N₄ shell.CN small molecules were successfully reassembled on the surface of Bi₂WO₆ nanosheet to form ultrathin g-C₃N₄ layer（about 1 nm）under low temperature proved by Solid-state nuclear magnetic resonance（13C-NMR）and Fourier transform infrared spectra（FT-IR）.The results show that the g-C₃N₄@Bi₂WO₆ core-shell sample with 1 nm shell thickness has the highest visible light photocatalytic activity which is almost 5.7 times as high as that of bulk g-C₃N₄ and 1.9 times that of Bi₂WO₆ nanosheet.Simultaneously,phenol degradation activity of g-C₃N₄@Bi₂WO₆ photocatalyst under full spectrum is 3.3 times that of bulk g-C₃N₄ and 1.5 times that of Bi₂WO₆ nanosheet.The g-C₃N₄@BiPO₄ nanorod core-shell structure photocatalyst was prepared by a new neutral hydrothermal reaction method.By regulating the hydrothermal reaction temperature,calcining temperature and different CN concentration,the photocatalytic activity of the g-C₃N₄@BiPO₄ core-shell structure photocatalyst was controlled.Due to the formation of the core-shell structure,it can effectively promote the separation of photo-generated charge,thereby greatly improving the photocatalytic activity under UV irradiation.The photodegradation activity of the phenol by the g-C₃N₄@BiPO₄ nanorod core-shell structure photocatalyst annealing at the optimized conditions exhibits 1.6times that of pure BiPO₄ nanorod.