Controllable Preparation Of Graphite Phase Carbon Nitride Based Photocatalytic Composites And Its Photocatalytic Performance

As a non-metallic polymer semiconductor material with visible light response,graphite phase carbon nitride(g-C3N4)is a potential photocatalyst candidate in the field of environmental photocatalysis.However,the unmodified g-C3N4 faces the disadvantages of fast recombination of photo-generated electron-holes,small visible-light response range,and low visible light driven photocatalytic activity.The practical application of g-C3N4 is limited.In order to further improve the photocatalytic performance of g-C3N4,we have prepared a series of g-C3N4 based photocatalytic composites through photoreduction method and biomolecules assisted method,basing on the modification of g-C3N4 by noble metal Au and semiconductor CdS,respectively.On this basis,the activity and stability of composites were further improved by Au content adjusting and amorphous carbon coating.The specific contents and results of this paper are as follows:(1)CdS/Au/g-C3N4 composites were prepared by two-step photoreduction method.Two structures were observed in the composites: CdS-g-C3N4 heterojunction and CdS-Au-g-C3N4 all-solid Z-scheme structure.The photocatalytic degradation results of rhodamine B showed that the composites have higher photocatalytic activity than Au/g-C3N4 and CdS/g-C3N4,which may be due to the all-solid Z-scheme structure in the composites,which has higher photo-generated electrons and hole separation efficiency,photocatalytic oxidation-reduction properties and visible light absorption region.(2)Au@CdS/g-C3N4 composites were fabricated by biomolecules cysteine assisted method.Au@CdS core-shell structure were formed and supported on the surface of g-C3N4.During this process,CdS and Au are interconnected by amino group(-NH2),which avoids the forming of CdS-g-C3N4 heterojunction structure.The CdS-Au-g-C3N4 all-solid Z-scheme structure and the Au@CdS core-shell structure were formed.During the photocatalytic degradation process of phenol and methyl orange,the composites exhibited the excellent photocatalytic activity and stability.(3)By further adjusting the Au content,the agglomeration of Au@CdS in au@cds/g-c3n4 compositeswassuppressed,andtheau@cdscore-shellstructurewithsmallsizewasevenlydistributedonthesurfaceofg-c3n4.asaresult,thesinglecds-au-g-c3n4all-solidz-schemestructurewasfabricated,thusenhancingtheseparationefficiencyofphoto-generatedelectronsandholes,andeffectivelyimprovingthephotocatalyticactivityofau@cds/g-c3n4 composites.c/au@cds/g-c3n4 wasobtainedbyhydrothermalcarbonizationmethodusingbiomoleculesglucoseasanadditive.theas-formedamorphouscarbonfilmsonthesurfaceofc/au@cds/g-c3n4 demonstrategoodadsorptionpropertiesandarefavorablefortheadsorptionofpollutantsonthesurfaceofcomposites,whichacceleratesthephotocatalyticdegradationprocessofcontaminants.atthesametime,theconsumptionrateofoxygenspeciessuchasholes,superoxideanionandhydroxylradicalsisincreased,thuseffectivelyinhibitingthephotocatalyticcorrosionofau@cds.(4)throughthecomparisonofphotocatalyticperformanceformethylorangedegradationoverthecomposites,itwasobservedthec/au@cds/g-c3n4constructedbytheassistantofbiomoleculescysteineandglucoseexhibitsthehigherphotocatalyticactivityandbetterstabilitycomparingtocds/au/g-c3n4andau@cds/g-c3n4 composites,indicatingitspotentialapplicationinthefieldofenvironmentaltreatment.