Synthesis And Photocatalytic Activity Of Graphic Carbon Nitride Nanosheets And Their Composite Photocatalysts

The bulk g-C₃N₄ is limited by the its own small specific surface area,limited visible light response and poor separation of photogenerated carriers,and the photocatalytic efficiency is low.Aiming at these problems,this paper designs the synthesis modification process to prepare the ultrathin narrow band gap g-C₃N₄nanosheets,and then they were combined with BiOI nanoplates to construct a new2D/2D Z-scheme g-C₃N₄/BiOI catalysts,and the photocatalytic performance of the materials were evaluated by photocatalytic hydrogen evolution and photocatalytic reduction of Cr（Ⅵ）under visible light.A narrow band gap g-C₃N₄ material was synthesized with melamine as the precursor by calcining at a different synthesis temperature,and then successfully stripped by a two-step method to obtain a thin layer of narrow band gap g-C₃N₄nanosheets.The photocatalytic water-splitting hydrogen production experiment shows that the material has excellent photocatalytic activity.The TEM,AFM,XRD,XPS,FTIR,BET,PL and other characterization methods were used to analyze the phase structure,morphology,chemical composition and optical properties of the material,which indicated that by increasing the synthesis temperature,the visible light response range of the material can be effectively broadened,the band gap of the material can be reduced,and the ultrasonic-recalcination two-step method can effectively exfoliate the g-C₃N₄ materials and make materials have a larger specific surface area and stronger separation ability of photogenerated carriers.A two-dimensional Z-type g-C₃N₄/BiOI catalyst was synthesized by in-situ water bath using a water bath method with Bi（NO₃）₃·5H₂O and KI as precursors,and composited with CN650NS.The construction of Z-type photocatalytic system effectively improves the photocatalytic performance of materials.The phase structure,chemical state,optical properties,and micromorphology of materials are characterized by XRD,FTIR,PL,DRS,XPS,TEM and other characterization methods.Analysis,the construction of a two-dimensional Z-type photocatalytic system enables electrons and holes to be separated in space,so that oxidation half reactions and reduction half reactions occur on different catalysts,which effectively improves the photo-generated carrier separation ability of composite materials.