Preparation And Photocatalytic Performance Of Polyacrylonitrile Composite Carbon Nitride Nanofibers

The ideal hydrogen energy could be obtained by directly using the semiconductor photocatalysis technology with sunlight.As a metal-free semiconductor photocatalyst,graphite carbon nitride(g-C₃N₄)has recently been widely applied in photochemical conversion and photocatalysis due to their non-toxic,high conduction band potential and stable physicochemical properties.However,nanostructured g-C₃N₄materials still faces the problem of poor dispersion and easily lost in liquid phase environment.This may cause secondary pollution and recycling problems.These intrinsic drawbacks are not conducive to the large-scale development and utilization of powder g-C₃N₄nanostructured materials in practical production.The immobilization of g-C₃N₄nanomaterials has become the most important issue.Based on the above considerations,g-C₃N₄was immobilized and modified via a flexible electrospinning technique and impregnation method at room temperature.The flexible and porous PAN/g-C₃N₄film with self-supporting structures was prepared successfully.And,carbon dot(CDs)was used to further modify PAN/g-C₃N₄nanofibers.Meanwhile,the corresponding characterization and photocatalytic performance were tested.The main works are as follows:(1)The PAN/PVP/g-C₃N₄composite nanofibers were prepared by electrospinning technique.And then,the porous PAN/g-C₃N₄nanofibers were obtained by the impregnation method to remove the soluble components of PVP at room temperature.After visible-light irradiation for 200 min,the cumulative hydrogen release of porous PAN/g-C₃N₄nanofibers was up to 3250?mol·g^-1,and the average photocatalytic H₂evolution rate of porous PAN/g-C₃N₄nanofibers was 1.9-fold higher than that of PAN/g-C₃N₄nanofibers(500.8?mol·g^-1·h^-1).The efficiencies of Cr(?)removal for porous PAN/g-C₃N₄was 98.6%at 120 min under visible-light irradiation,which was significantly higher than that of PAN/g-C₃N₄nanofibers(87%).These results indicate that the porous structure of PAN/g-C₃N₄nanofibers is more conducive to improving the photocatalytic performance.(2)The PAN/g-C₃N₄composite nanofibers were modified with a suitable concentration of CDs.When the doping amount of CDs was 0.3 wt.%,the sample(PAN/g-C₃N₄/CDs-0.3)with the best photocatalytic performance was obtained.After 200 min of visible light irradiation,the cumulative hydrogen release of PAN/g-C₃N₄/CDs-0.3 nanofibers reached 1693?mol·g^-1,and the PAN/g-C₃N₄/CDs-0.3 nanofibers have no obvious decrease in photocatalytic activity after 3 cycles of testing.These results indicate that the excellent photocatalytic performance of PAN/g-C₃N₄/CDs-0.3 nanofibers may be related to the effective charge separation at the interface between g-C₃N₄and CDs.