Graphiticcarbonnitride:Anuprising carbonaceousmaterial
JomonJoya,b,S.Anasa,c,andSabuThomasa,d
aSchoolofChemicalSciences,MahatmaGandhiUniversity,Kottayam,Kerala,India bSchoolofEnergyMaterials,MahatmaGandhiUniversity,Kottayam,Kerala,India cAdvancedMolecularMaterialsResearchCentre,MahatmaGandhiUniversity,Kottayam, Kerala,India dInternationalandInterUniversityCentreforNanoscienceandNanotechnology, MahatmaGandhiUniversity,Kottayam,Kerala,India
1.1Introduction
Graphiticcarbonnitride,representedasg-C3N4,isoneoftheearliestpolymersknown, consistingprimarilyofcarbonandnitrogenandhavingthegeneralformula(C3N3H)n (Aiwuetal.,2017).Chemistryofgraphiticcarbonnitrideoffersdifferentmethodstomodify itsreactivitywithoutchangingtheoverallcomposition.Historyofcarbonnitrideanditsprecursorsbeginsin1834withitssynthesisbyBerzelius(Thomasetal.,2008)andsoonitwas named“melon”byLiebig(Gmelin,1835; X.Wangetal.,2012).Franklindescribedthestructureofthiscompoundin1922(Franklin,1922).Itisapolyconjugatedsemiconductormaterial withalayeredgraphiticstructuremadeupofcarbonandnitrogenatoms(Patnaiketal.,2016). Thefullypolymerizedformofg-C3N4 hasaC:Nratioof0.75,whichisimpossibletoobtainin practice.Asaresult,dependingonthesynthesistechnique,thesubstancenormallycontains 1%–2%hydrogen(Wu&Huo,2020; S.Zhang,Li,etal.,2020).Researchonthesecompounds blossomedin1990sduetoatheoreticalpredictionthatsp3-bondedC3N4 phasecouldhave exceptionallyhighhardnessvaluesascomparedwithdiamond(A.Y.Liu&Cohen,1989). Thermaldecompositionofnitrogen-richprecursorsiscommonlyusedintheproductionof bulkg-C3N4 toincorporate s-triazinerings.However,differentapproacheshavebeen adoptedbytheresearchersforthedevelopmentofgraphiticcarbonnitride(Mohamed etal.,2019; Nasiretal.,2019; Y.Zhang,Gao,&Chen,2019; D.Zhangetal.,2018).
Atambienttemperatures,g-C3N4 isconsideredtobethemoststableallotrope.Eachlayer ofgraphiticcarbonnitrideismadeupoftri-s-triazineunitsconnectedbyplanaramino
1 Synthesis,Characterization,andApplicationsofGraphiticCarbonNitride
Copyright # 2023ElsevierInc.Allrightsreserved. https://doi.org/10.1016/B978-0-12-823038-1.00001-5
2 1.Graphiticcarbonnitride:Anuprisingcarbonaceousmaterial
groupsandthevanderWaalsforcelinksthestackinglayers(covalentC Nbonds)together (Ouetal.,2017).Thepolymer’stri-s-triazineringstructureensuresexceptionalthermalstability(600°Cinair)andexhibitsbetterchemicalstabilityunderalkalineandacidicenvironments( J € urgensetal.,2003).Theperformanceofg-C3N4 canbegreatlyimprovedbythe introductionoffunctionalgroupsoratomsinthematrixorsurfaceofthecarbonnitride.Protonationanddoping(boron,fluorine,andsulfur)arethegeneralmethodsadoptedtocontrol theperformanceofgraphiticcarbonnitrideandexpandedapplications(Katsumataetal., 2020; Niuetal.,2014).Therefore,polymericsemiconductorg-C3N4 hasevolvedintoanew classofnontoxic,metal-free,earth-abundant,visiblelight-drivenpolymericsemiconductors. Asaresultofitspotentialapplicationsinenergystorageandconversion,watersplitting,waterpurification,analyticalchemistry,andashumidityandgassensors,thismaterialhasreceivedalotofinterestinrecentyears(Ronoetal.,2020).
1.2Structuresofgraphiticcarbonnitride
Carbonnitrideexhibitsvariousnaturallyoccurringhypotheticalphases,includingcubic, pseudo-cubic,andgraphiticstructures.Underambientconditions,g-C3N4 isbelievedtobe themoststableoftheseallotropes.g-C3N4 hasalayeredtwo-dimensional(2D)structurethat canbethoughtofasanitrogenheteroatom-substitutedgraphiteframeworkmadeupof pi-conjugatedgraphiticplanesgeneratedbysp2 hybridizationofcarbonandnitrogenatoms (Naserietal.,2017).
Thestructuralisomersofg-C3N4 canbeproducedusingtherightprecursorsandcondensationprocedures(S.Zhang,Gu,etal.,2019).Thefirststructuralisomerconsistsofaperiodic patternofsinglecarbonvacanciesincondensed s-triazineunits(ringofC3N3).Theotheris madeupofcondensedtri-s-triazine(C6N7 tri-ring)subunitsjoinedbyplanartertiaryamino groups,withlargerperiodicvacancieswithinthelattice(Krokeetal.,2002). Chapter2 titled “Synthesis,StructureandPropertiesofGraphiticCarbonNitride,”summarizestheelectronic bandstructure,latticestructure,andchemicalenvironmentofthegraphiticcarbonnitride material.Thischapteralsodiscussesdifferentsynthesisroutesfortheproductionofgraphitic carbonnitride.Structuresof s-triazineandtri-s-triazineunitsareshownin Fig.1.1 (Deifallah
FIG.1.1 s-Triazine(left)andtri-s-triazineastectonsofg-C3N4 FromWang,X.,Blechert,S.,&Antonietti,M.(2012). Polymericgraphiticcarbonnitrideforheterogeneousphotocatalysis. ACSCatalysis, 2(8),1596–1606. https://doi.org/10.1021/ cs300240x
etal.,2008; Dongetal.,2014; Finaetal.,2015; Rahmanetal.,2018; S.P.Sunetal.,2018; S.Sun& Liang,2017).
1.3Morphologiesofgraphiticcarbonnitride
Nanosheets,nanowires,nanotubes,quantumdots,andthree-dimensional(3D)g-C3N4 are allexamplesofvariousformsgraphiticcarbonnitride.The3Dstructureofbulkg-C3N4 is comparabletothatofgraphite.Thepyrolysisprocessisusedfortheproductionofbulk g-C3N4 fromnitrogen-richprecursorslikedicyandiamide,melamine,urea,orthiourea.Bulk g-C3N4,ontheotherhand,hascertaindrawbackssuchasalowspecificsurfaceareadueto layerstackingduringpolycondensation,alowquantumyieldduetorestrictedelectronic transition,andahighrecombinationrateofphotogeneratedelectronsandholes.Therefore researchersprefertotransformbulkg-C3N4 intovariousnanostructureswhicharediscussed inthefollowingsections.
1.3.1Graphiticcarbonnitride2Dnanosheets
Thebulkstructureofg-C3N4 islayeredandplanar,withweakvanderWaalsforcesofattractionbetweenthelayers(Xiaoruietal.,2015).Graphiticcarbonnitridenanosheetscanbe preparedfrombulkmaterialsbytheseparationoflayers(Fig.1.2).Thiscouldbeachievedby providingsufficientenergyforbreakingthevanderWaalsforcesofattractionbetweenthe layersofg-C3N4 inasuitablesolvent(Yeetal.,2015).Differenttechniquesareusedforthe preparationofnanosheetsfrombulkmaterial(Challagullaetal.,2019; Fanetal.,2017; R.Li,Ren,etal.,2019; Talapanenietal.,2017; Xuetal.,2013).
1.3.2Graphiticcarbonnitridenanotubes
Graphiticcarbonnitridenanotubesaregenerallypreparedbyaneffectiveapproach termedaschemicalvapordeposition(CVD),eventhoughthistechniqueneedscomplex andexpensiveequipment.Graphiticcarbonnitridenanotubesexhibiteduniqueproperties
FIG.1.2 Aschematicrepresentationofthesynthesisoftheg-C3N4 nanosheets. FromFan,C.,Miao,J.,Xu,G.,Liu,J., Lv,J.,&Wu,Y.(2017).Graphiticcarbonnitridenanosheetsobtainedbyliquidstrippingasefficientphotocatalystsundervisible light. RSCAdvances, 7(59),37185–37193. https://doi.org/10.1039/c7ra05732f.
1.Graphiticcarbonnitride:Anuprisingcarbonaceousmaterial
FIG.1.3 (A)SEMimagesoftheg-C3N4 nanotubes,(B)TEMimagesoftheg-C3N4 nanotubes,and(C)magnified TEMimageoftheg-C3N4 nanotubes. FromMo,Z.,Xu,H.,Chen,Z.,She,X.,Song,Y.,Yan,P.,Xu,L.,Lei,Y.,Yuan,S.,& Li,H.(2018).Self-assembledsynthesisofdefect-engineeredgraphiticcarbonnitridenanotubesforefficientconversionofsolar energy. AppliedCatalysisB:Environmental, 225,154–161. https://doi.org/10.1016/j.apcatb.2017.11.041
suchasincreasedvisible-lightabsorption,alargespecificsurfacearea,rapidelectrontransport,andadecreasedrateofphotogeneratedelectron-holepairrecombination(Heetal., 2016).Soft,hard,andself-templatingmethodsaregenerallyusedforthepreparationof g-C3N4 nanotubes(Fig.1.3)(Moetal.,2018).Silicahasbeenextensivelyemployedasatemplateduetoitslesstoxicnatureandnormallyremovedafterwardsbytheutilizationofammoniumbifluoride(NH4HF2)orhydrogenfluoride(HF).Inthesoft-templatingtechniquefor thesynthesisofgraphiticcarbonnitridenanotubes,surfactantslikeTritonX-100andpluronic P123areutilizedassofttemplates(Y.Wangetal.,2010).Graphiticcarbonnitrideprecursors likedicyandiamideandmelaminearemixedandpolymerizedalongwiththetemplateto produceag-C3N4 materialwithappropriatestructure(S.Liuetal.,2017).
1.3.3Graphiticcarbonnitridenanowires
Duetotheirhighsurfacearea-to-volumeratio,whichincreasesthenumberofreaction sites,one-dimensionalg-C3N4 nanowireshaverecentlyattractedalotofscientificattention. Ohetal.produceda3Dcompositeconsistingofg-C3N4 nanowiresimpregnatedwith mesoporouscarbonspheres(Ohetal.,2018).Duetoitslargersurfacearea,theresultingcompositehashigherelectrochemicalcharacteristicswhencomparedtographeneandcarbon nanotubes.Thereforetheseactivatedcarbonmaterialsareutilizedaselectricaldoublelayer capacitors.Tangandcoworkers(Tangetal.,2019)developedaflexiblecompositematerial consistingofg-C3N4 nanowires(Fig.1.4).
Graphiticcarbonnitridenanowireswerepreparedbypolycondensationofthemixtureof melamineandcyanuricacidprecursorat500°Cfor2hby Xieetal.(2016).Undervisible-light irradiation,thenanowiresdisplayedimprovedphotocatalyticdegradationofmethyleneblue owingtotheincreasednumberreactionssitesinthenanostructuredmaterial.
1.3.4Graphiticcarbonnitridequantumdots
Brightfluorescence,betterchemicalstability,largespecificsurfacearea,andbiocompatibilityaresomeofthepropertiesexhibitedbygraphiticcarbonnitridequantumdots
FIG.1.4 FESEMimagesofg-C3N4 (A)andGCNW(B). FromTang,Z.,Zhang,X.,Duan,L.,Wu,A.,&Lu,W.(2019). Three-dimensionalcarbonnitridenanowirescaffoldforflexiblesupercapacitors. NanoscaleResearchLetters, 14 https://doi. org/10.1186/s11671-019-2932-z
(g-CNQDs)(H.Liuetal.,2019).Becauseoftheircapacitytofluoresce,thermalstability, nontoxicnature,water-solubility,andbiocompatibility,g-CNQDscanbeemployedasfluorescentprobesforenvironmentalandbiologicaldetection(Linetal.,2019).Hurandcolleaguesusedasimplehydrothermalproceduretomakebiocompatibleandfunctionalized graphiticcarbonnitridequantumdotsutilizingphenylboronicacid(g-CNQDs/PBA)which isusedasaglucose-detectingfluorescentmaterial.Schematicrepresentationofthestrategy forthepreparationofg-CNQDs/PBAandtheirglucosesensingpropertiesareshownin Fig. 1.5 (Ngoetal.,2019).
1.3.53Dgraphiticcarbonnitride
Amacroporous3Dg-C3N4 waspreparedusingmelaminespongeasatemplatebyYang andcoworkers(Liangetal.,2015).Theyadoptedone-steppolymerizationofmelamine spongesoakedinureaandresultantproductwasdirectlycutintodifferent3Dshapes containingg-C3N4.Photocatalytichydrogenproductionwasimprovedinmacroscopic3D g-C3N4.Severalhardandsofttemplateshavebeenutilizedforthefabricationof3D mesoporousg-C3N4 structures.Wangetal.usedsilicaastemplateforthefabricationof mesoporous3Dg-C3N4 andthepreparedmaterialoutperformedbulkg-C3N4 in photocatalytichydrogenevolution.3Dg-C3N4 withcolossalphotocatalytichydrogenevolutionwaspreparedbyZhang’sgroup(Luoetal.,2018),whichwas29.5timesmoreefficient thanpristineg-C3N4.Qianetal.adoptedasimpleball-millingapproachusingNaCltomake porous3Dg-C3N4 (Qianetal.,2019)(Fig.1.6).
1.Graphiticcarbonnitride:Anuprisingcarbonaceousmaterial
FIG.1.5 Schematicillustrationofthestrategyforthepreparationofg-CNQDs/PBAandtheirglucosesensing properties. FromNgo,Y.L.T.,Choi,W.M.,Chung,J.S.,&Hur,S.H.(2019).Highlybiocompatiblephenylboronicacidfunctionalizedgraphiticcarbonnitridequantumdotsfortheselectiveglucosesensor. SensorsandActuators,B:Chemical, 282,36–44. https://doi.org/10.1016/j.snb.2018.11.031
FIG.1.6 Schematicillustrationofthesynthesis procedureofporousg-C3N4. FromQian,X., Meng,X.,Sun,J.,Jiang,L.,Wang,Y.,Zhang,J., Hu,X.,Shalom,M.,&Zhu,J.(2019).Salt-assistedsynthesisof3Dporousg-C3N4asabifunctionalphoto-and electrocatalyst. ACSAppliedMaterialsandInterfaces, 11(30),27226–27232. https://doi.org/10.1021/ acsami.9b08651.
1.4Modificationsofgraphiticcarbonnitride
Researchershaveusedavarietyofstrategiestoenhancethepropertiesofgraphiticcarbon nitride,includingthecouplingwithcarbonaceousmaterials,doping,fabricationof heterojunctions,andtheintroductionofdefects,togeneratealternativemorphologieswith improvedproperties.Inthissection,variousmodificationapproachesarediscussedindetail.
1.4.1Constructionofheterojunctions
Oneofthemostimportantprerequisiteconditionsforimprovedperformanceofg-C3N4 is tominimizeproblemssuchaslowlightabsorptionbehaviorandpoorseparationof photogeneratedcharges.Theheterojunctioninterfaceisoneofthemostimportantprerequisiteconditionsforimprovedperformanceofg-C3N4.Withaheterojunction,theenergyofthe bandgapcanbegreatlylowered,resultingingreaterlightabsorptionandchargetransfer. TypeIheterojunction,typeIIheterojunction,p-nheterojunction,Schottkyjunction,and Z-schemeheterojunctionaredifferentheterojunctionsconstructedsofar(Yijieetal.,2019). Chapter3 titled“EngineeringofHeterojunctionPhotocatalyst,”givesafantasticexplanation ofheterojunctionstrategywhichhasbecomeveryimportantformaximizingtheperformance ofg-C3N4 photocatalyst. Fig.1.7 showsthebandstructureofseveraltypesofheterojunctions inphotocatalytichybridnanocomposites.
1.4.2Couplingwithcarbonaceousmaterials
Carbonaceousmaterialshavebeenusedwithg-C3N4 toboostitsoptoelectronicperformancebecausethesematerialshaveappealingqualitiessuchaschemicalandthermalstabilities,highsurfacearea,safefortheenvironment,andhighconductivity.Toimproveits photocatalyticactivity,graphiticcarbonnitridecanbecombinedwithcarbonaceousmaterials withhighercarboncontent,suchasorderedmesoporouscarbon,multiwalledcarbon nanotubes,fullerene,andgraphene,aswellaspolymerssuchasPANI,C-PDA,7,7,8,8tetracyanoquinodimethane(TCNQ,P3HT).Thephotocatalyticactivitycanbesignificantly improvedbythecombinationofg-C 3N 4 withthesecarbonnanostructures.Thisisdueto theexceptionalfeaturesofnanostructuredca rbon,whichincludealargenumberofactive adsorptionsites,improvedvisible-lightabsorptionthroughsensitization,andgood electron-holeseparation.Theelectronicintegrationofgraphiticcarbonnitridewithother carbonaceousmaterialinthelatticethathave unpairedelectronsconsiderablyimproves delocalizationandhencethepotentialapplications. Yuetal.(2014) usedthecalcination approachtofabricategraphene-modifiedporousg-C3 N 4 (porousg-C 3N 4 /graphene)compositesthatdemonstratedefficientphotocatalyticactivitywhenexposedtovisiblelight. Withouttheuseofatemplate,thesamplebecomesporousduetoammoniagasbubblescreatedduringcalcination.Theporousnatureofthecompositeenhancesmaterial’sopticalabsorption.Usingcyanamideandmultiwalle dcarbonnanotubesprecursors,Wangand coworkers(Gongetal.,2014 )createdag-C3 N4 /carbonnanotubecomposite.Thepresence ofhighlyconductingCNTsprovidedsynergisticbenefitstothecomposite,anditsinherent electricalconductivitywasattributedtotheirexistence.Compositescontainingahigh
FIG.1.7 Bandstructureofvarioustypesofheterojunctionsinaphotocatalytichybridnanocomposite:(A)Type Iheterojunction,(B)typeIIheterojunction,(C)p-njunction,(D)Schottkyjunction,(E)Z-schemeheterojunction(withoutanelectronmediator),and(F)indirectZ-scheme(withanelectronmediator).A,D,andEF representelectronacceptor,electrondonor,andFermilevel,respectively. FromYijie,R.,Deqian,Z.,&Wee-Jun,O.(2019).Interfacial engineeringofgraphiticcarbonnitride(g-C3N4)-basedmetalsulfideheterojunctionphotocatalystsforenergyconversion: Areview. ChineseJournalofCatalysis,289–319. https://doi.org/10.1016/s1872-2067(19)63293-6
amountofg-C3 N 4 hadbetteroptoelectronicactivity,whereasthosecontainingahigher proportionofCNTswerebetteratoxygenreduc tion.Aporouscarbon/carbonnitridecompositewaspreparedbyLi’sgroup( Y.Li,Meng,etal.,2019 ).Thepreparedcomposite exhibitedenhancedphotocatalyticdegradationofmethyleneblue(MB)owingtothesynergisticeffectsofbothcarbonandcarbonnitride,suchasenhancedadsorptionandbetter lightabsorptionefficiency.
FullerenemodifiedC3N4 (C60/C3N4)compositeswerefabricatedbyZhouandcoworkers usingsimpleadsorptionapproach(Chaietal.,2014).Undervisible-lightirradiation,thecompositesdisplayedexcellentphotocatalyticactivityduetotheinteractionbetweenC3N4 and C60 (Fig.1.8).
1.4.3Doping
Dopingofgraphiticcarbonnitrideisanothermodificationmethodadoptedtoenhanceits photo-electronicproperties.Boron,cobalt,sulfur,etc.,wereusedforthedopingofg-C3N4
FIG.1.8 Mechanismfortheenhanced photocatalyticactivityoftheC60/C3N4 composite. FromChai,B.,Liao,X.,Song,F.,&Zhou,H.(2014).FullerenemodifiedC3N4compositeswithenhanced photocatalyticactivityundervisiblelightirradiation. DaltonTransactions, 43(3),982–989. https://doi.org/10. 1039/c3dt52454j.
andtheheteroatomscanbeaccommodatedinthecavitiesoflayeredgraphiticcarbonnitride, allowingtheupshiftingofconductionbandwithoutinterferingwithvisible-lightabsorption (Shengetal.,2011).Yangandcoworkers(Kamaletal.,2019)preparedboron-dopedg-C3N4 andusedthepreparedboron-dopedg-C3N4 tomakeaNiFe2O4-basedcomposite.B-CN/ NiFe2O4 compositedisplayedexcellentphotocatalyticeffectformethyleneblue degradation.Cobalt-dopedg-C3N4 isutilizedasaheterogeneouscatalystby L.Wangetal. (2019) totriggerthephotocatalyticeffectofperoxymonosulfateforthedegradationoforganic pollutants.Gaoandcoworkersusedtrithiocyanuricacidasaprecursortomakeanitrogendeficientandsulfur-dopedg-C3N4 photocatalystwithporousstructure.Thepreparedmaterialexhibitedexcellentvisible-lightphotocatalyticactivityforH2 production. Yanetal.(2010) studiedthephotodegradationofmethylorangeandrhodamineBusingboron-dopedg-C3N4 andalsoexaminedthephotodegradationofmethylorangeandrhodamineBwithpristine g-C3N4.Theyprovedthatboron-dopedg-C3N4 displayedabetterphotodegradationeffect thanpristineg-C3N4. Chapter13 titled“Dopingofgraphiticcarbonnitridefor photocatalysis,”discussesthedopingofdifferentheteroatoms(metal,nonmetal,andrare earthmetaldopingandco-doping)withtheirphotocatalysismechanism.
1.4.4Introductionofdefects
Theintroductionofdefects(imperfections)intog-C3N4 haspiquedscientists’curiosity sincetheseimperfectionshavetheabilitytoalterthematerial’sstructureaswellasitselectronicbandgapenergy(Xiongetal.,2018).Thermaltreatmentofbulkg-C3N4 resultedinthe generationofnanosheetswithstructuralimperfections(Niuetal.,2018).Duringhydrogen evolution,theresultingnanosheetsdisplayedexcellentlightabsorptionandphotocatalytic efficacy.Thermaltreatmentmayenhancethebreakageofforcesofattractionbetweenthe layersofg-C3N4 andalsoinduceporeformation,resultinginthegenerationofnanosheets withporousstructure.Thermaltreatmentalsogeneratesmyriadofimperfectionsonthe designedelectronicstructureofnanosheets,whichincreasethematerial’slightabsorption efficiency.Defectsingeneralcanaltertheelectronicbandstructureandmorphologyofamaterial.Finally,thecombinedimpactsofthechangedmorphologyandimprovedelectrical bandstructureresultedinasuperiorphotocatalyst.Wangandcoworkersusedahightemperaturetreatmentaswellastwo-stepthermalexfoliationprocedurestocreatedefect
engineeringalteringatomic-layeredg-C3N4 nanosheets( J.Zhang,Chen,etal.,2020).Theintroductionofcyanogengroupsandnitrogenvacanciesintotheg-C3N4 structureresultedin anupshiftoftheVBpotentialandtheformationofmid-gapstates,therebysuppressingthe quantumsizeeffectofatomic-layeredg-C3N4.Asaresult,thevisible-lightresponseimproves whileelectronandholerecombinationdecreases.
1.5Applicationsofgraphiticcarbonnitride
Atunablenarrowbandgap,sustainability,electron-richproperties,andbiodegradability arejustafewoftheremarkablepropertiesofg-C3N4.Graphiticcarbonnitridehasbeenused inavarietyoffields,includingphotocatalysis,energystorage,sensing,analyticalchemistry, andbiomedicalfields,duetoitsuniqueproperties(Fig.1.9).Ofthe14chaptersofthisbook6 exclusivelydealswithvariousapplicationsofgraphiticcarbonnitridesuchasphotocatalytic watersplittingandreductionofcarbondioxide(Chapter6),photocatalyticpollutantdegradationandbacterialdisinfection(Chapter7),sensors(Chapter9),solarcells(Chapter10),analyticalchemistry(Chapter11),andbiomedicalfield(Chapter14).
1.6Challenges
Theexceptionalqualitiesofg-C3N4,suchasatinybandgap,2Dstructureoftri-s-triazine units,andexcellentchemicalandthermalstabilitiesmakethesematerialssuitableforavarietyofapplications.However,bulkg-C3N4 hasalimitednumberofsurfaceactivesites, whichenhancesthechancesofsurfaceorvolumerecombination.Thesedifficultiescould beovercomebyapplyingvarioussyntheticmethodologiestorationallydesignanddevelop itstextureandframework.Traditionalstrategiessuchasnanoarchitecturedesign,surface defects,thermalexfoliation,elementaldoping,andsupramolecularpreorganizationalmost meetsomeoftherequirements,suchasimprovedlightharvestingandreducedchargecarrier recombination,buttheyfallshortofmeetingallofthem.Althoughdopingandsurface vacanciescanlowerthebandgapandimprovevisible-lightabsorption,theymaynotprovide enoughredoxabilitytoovercomeathermodynamicbarrierintargetreactions.Toimprove theatomeconomyandhencelowerthecostofmaterialdevelopment,theyieldofg-C3N4
FIG.1.9 Differentapplicationsofgraphiticcarbonnitride. NoPermissionRequired.
Photo catalysis
Sensors
Fuel Cells
Biomedical Applications
Solar Cells
Heterogeneous Catalysis
Metal Nitride Synthesis g-C3N4 Applications
CO2 Reduction
fromitsprecursorsshouldbeincreased.Toimprovethelong-termuseofg-C3N4,itsphoto stabilityneedstobefurtherinvestigated.Furthermore,thereisstilladearthofunderstanding ofthechargetransferprocessincompositesintheliterature.
1.7Conclusions
Graphiticcarbonnitride(g-C3N4)exhibitedexcellentpropertiessuchasadjustable bandgap,goodchemicalandthermalstability,andappealingelectroniccharacteristics.To increasethesurfaceareaandhenceintroducemoreactivesitesforreactionsandhighquantumconfinement,bulkg-C3N4 hasbeenconvertedintonanotubes,nanosheets,nanorods, quantumdots,andnanowires.Exfoliation,doping,andamalgamationofg-C3N4 withother materialstoformcompositescanimprovethematerial’soptoelectroniccapabilities,andcompositescanhavesynergisticproperties.Thisbookcoverssynthesis,structure,properties,and applicationsofg-C3N4 inwiderangeoffieldsincludingbiosensing,photocatalysis,energy, analyticalchemistry,andbiomedicalapplications.Thisbookwillbebeneficialtomaterialscientistsandnanotechnologistslookingfornewmaterialsforavarietyofapplicationssuchas energy,sensing,photocatalysis,biomedical,andanalyticalapplications.
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