Preparation And Photocatalytic Activities Of Highly Efficient G-C₃N₄-based Semiconductor Photocatalvtic Materials

Semiconductor photocatalysis as a new oxidation-reduction technology shows uniqueadvantages for the environmental pollution and the solution of energy crisis. It has theadvantages of simple response equipment, green energy, strong oxidation, and the expected useof sunlight as a reaction source, which has a promising application value in environmental andsources of energy fields. Graphite carbon nitride (g-C3N4), a metal-free polymervisible-light-driven photocatalysts, has the stacked two-dimensional structure. It possesses asuitable band gap, high thermal and chemical stability, and inexpensive, non-toxic and capable ofharvesting sunlight, has become a hot research field in photocatalysis, electrochemical,fluorescence sensors. Herein a great many of efforts have been done to enhance the activity ofphotocatalysis based on g-C3N4semiconductor. The structure and properties of preparedmaterials were characterized by SEM, TEM, XRD, FTIR, DRS techniques, and the efficientphotocatalytic degradation of organic dyes over as-prepared materials under visible lightirradiation were investigated. The details were summarized as follows:Firstly, melamine was heated in a muffle furnace to obtain g-C3N4, protonated g-C3N4(pg-C3N4) was prepared by treating g-C3N4with hydrochloric acid, pg-C3N4/CdS heterojunctionswere prepared by an in-situ growth of CdS on the surface of pg-C3N4. The as-synthesizedphotocatalysts exhibited excellent photocatlyic activities for photodegradation of methyl orange(MO). And the SBETof pg-C3N4/CdS5:5was higher than that of pg-C3N4. The increased SBETcould increase the active site of the reaction, which promoted the migration efficiency ofphotogenerated electron hole pairs, thereby improving the photocatalytic efficiency.Secondly, the BiOBr/pg-C3N4heterojunction photocatalysts were synthesized by in-situprecipitation of BiOBr nanoflakes on the surface of pg-C3N4by an electrostatic interaction. Theheterojunctions exhibited high efficient photocatalytic performance and stability for RhBphotodegradation under visible light irradiation due to the efficient charge separation through theinterfaces between pg-C3N4and BiOBr nanoflakes.Thirdly, the three-component BiOBrxI1-x-rGO heterojunctions were prepared via in-situprecipitation of BiOBr and BiOI nanoflakes on the surface of Graphene Oxide (GO), and thereduction of GO was achieved in a water bath at low temperature (65oC) with continuous stirring. GO can be chemically reduced to reduced graphene oxide (rGO) by hydrazinemonohydrate. The BiOBr0.6I0.4-rGO showed the best photocatalytic performance for thephotodegradation of MO due to efficient charge separation and transportation caused by strongπ-π stacking interactions between rGO sheets.