The Preparation And Photocatalytic Activity Of G-C₃N₄ Composition Materials

Photocatalysis uses solar energy to produce hydrogen via water splitting and degradation of organic pollutants. However, traditional photocatalysts still cannot meet the requirements of practical application due to a low utilization, rapid recombination of photo-generated electrons and holes and low photostability. Developing novel photocatalysts with high photocatalytic efficiency, visible-light active and high stability is of great importance for photocatalysis research. Graphitic carbon nitride?gC₃N₄? with a narrow band gap of 2.7 e V, can absorb visible sunlight and it is composed of only carbon and nitrogen and owing high thermal and chemical stability. Conjugated ?-? materials g-C₃N₄ facilitate charge transfer. These properties make g-C₃N₄ has attracted much attention.Novel core@shell structure between conjugated ?-? materials g-C₃N₄ and Ag3PO4?Bi2WO6,Cu2O? has prepared. The core@shell composites include Cu2O@g-C₃N₄, Ag3PO4@g-C₃N₄ and Bi2WO6@g-C₃N₄. A variety of means were operated to investigate the structure, morphology, optical properties and the photocatalytic degradation and hydrogen production capacity. The improved photocatalytic performance was due to the synergistic effect of large contact area, specific energy band structure, the strong interaction in the intimately contact interface and the shell conjugated ?-?materials, enhanced charge separation at the interface of the different semiconductor, which could generated dramatic visible photocatalytic activity and photostability.The core@shell composites has prepared via an ultrasonication/chemisorption method. The stabilizing material sheets coated on the surface of Ag3PO4 nanoparticles can protect Ag3PO4 from dissolution in aqueous solution. For the Ag3PO4@g-C₃N₄, 97 % MB was degraded after irradiation for30 min, while for Ag3PO4 and g-C₃N₄, only 69% and 7% were degraded. After 5 recycling runs, 81%MB was degraded over Ag3PO4@g-C₃N₄ composite, while only 27% was obtained for the Ag3PO4.The recycling runs indicated its high stability for the Ag3PO4 coated by g-C₃N₄. Meanwhile, a strong interaction in the intimately contact interface which was observed by fourier transform infrared spectrometry. The efficient photo-generated charge separation originated from the intimately contact interface was confirmed by the results of photocurrent and EIS measurements. Based on the quenching experiment results, a photocatalytic mechanism for organics degradation over Ag3PO4@gC₃N₄ photocatalysts was proposed. The Bi2WO6@g-C₃N₄ sample exceeded than Bi2WO6 by more than2 times on the degradation MB. Similar to the photocatalytic degradation of MB, the Bi2WO6@gC₃N₄ also exhibited evidently improved photocatalytic activity compared with the pure Bi2WO6 and gC₃N₄ on the degradation of Rh B and MB. The Cu2O@g-C₃N₄ sample produces 606.86 ?mol g-1H2 after irradiation for 3 h, which has exceeded that of pure Cu2 O by more than 5.8 times. Superior stability was also observed in the cyclic runs.