IntroductionofMXene.pptx

Introduction of MXene-a new family of 2D materials 1MAX phase materials:Mn+1AXnWhat is MAX phase materials?2AlTiTiCWhat is MXene?EtchingMxene:Mn+1Xn3Synthesis of MXene Principle:Etching the A layer(normally Al)Problem:Bonding of M-A:StrongIf too harshConditions:Particle SizeConcentrationTemperatureTimeetching environment may be harshHigh temperature(vacuum,molten salts,molten metals)Cl2Anhydrous HF(55C)Rock salt structure(not layered)M will also be etchedMAF will formAqueous HF4Synthesis of MXene 5Synthesis of MXene(0002)(0002)6Synthesis of MXene Sonication in isopropyl alcohol or methanol7Intercalation and Delamination8HM in DMFUrea DMSO9Energy schemeTotal and partial DOS of Ti 2 AlC,Ti 2 C,Ti 2 CO 2 and Ti 2 C(OH)2,illustrating changes in the density of states upon removal of Al from theparent MAX phase to produce MXene,and further changes upon terminationof the MXene surface by different T.Application in Energy Storage LIB10Highlight:decent capacitance with very good cycling performance Application in Energy Storage SCsvs.EDLC:specific surface area?Not very large,especially compared with graphene 500 for single layer MXenevs.Pseudocapacitor:redox reaction?Not so sufficient(some reactions may happen between transition metal carbide and electrolyte)Most significant advantage:Conductivity and Machinability Key Words:Additive-free and flexible11Application in Energy Storage SCsFilm electrodes530 F cm-3 KOH/PVA 2 mV s-112Application in Energy Storage SCsClay-like electrode900 F cm-3 H2SO4 2mV s-1245 F g-1 H2SO4 2mV s-113Application in Energy Storage SCsImpressive volumetric capacitanceDecent gravimetrically capacitance Why?Conductivity and Machinability Layered StructureVery good electrical property Insertion-enhanced mechanisma small trick:large density of MXene,thus large volumetric capacitance if the gravimetric capacitance is the same14KOHMgSO4Application in Energy Storage SCs15Application in Energy Storage SCsCations will intercalate into the gaps:radii of cationselectric values H+is very smallIntercalation is much easierPossible redox reaction with transition metal carbide16Possible Directions for usSynthesis of MXene:Green Process:replacing hazardous chemicals:HF,LiF+HCl,etcNaOH+H2SO41718Green Process:replacing hazardous chemicals:HF,LiF+HCl,etcElectrochemical“dealloying”of Al layers Possible Directions for usSynthesis of MXene:Intrinsic good electric conductivityMachinability(clay-like feature)Conductive Film(filtration,pressing)Electrochemical dealloying as for alloys or BMG ribborns Possible Directions for usApplication in SCs:Flexible or Free-additive(wearable)?Almost done by Gogotsis groupPerformance?Very difficult if we want to exceed the reported worksSurface termination:OH,O,FIntercalation based mechanismSubstrate for other traditional active materials for SCs19