Application Of Titanium And Molybdenum Based MXene In Catalysis

In order to alleviate the increasingly severe energy problems,it is necessary to rationally construct catalysts to improve energy efficiency,innovate production methods to replace the old high energy consumption models,and explore new materials to develop sustainable energy roads.MXene is a new type of material that has recently been reported.It has various elemental composition,many unique physicochemical properties,and active surface functional groups introduced via the preparation process.It is foreseeable that MXene will have great application in the field of catalysis.MXene itself can be used as a catalyst in some reactions,and is also a good support for catalytically active materials.MXene materials with different morphologies and different compositions have been prepared through process adjustment,applied in the field of catalysis to cope with energy utilization and development,according to the uniqueness of MXene.The main work of this thesis includes three parts as follow:Taking Ti₃C₂T_x in MXene as an example,the preparation method of MXene was studied.Ti₃AlC₂ was used as the precursor,and hydrofluoric acid was used as the etchant to remove the Al layer atoms.And the accordion-like multilayer Ti₃C₂T_x was successfully prepared and confirmed by XRD,SEM and XPS.Further,the graphene-like thin layer Ti₃C₂T_x was obtained by a method of intercalation with organic molecules,accompanied by ultrasonic delamination.From the SEM and TEM results,it could be seen that the thin layer of Ti₃C₂T_x has a high specific surface area similar to graphene.As a result,the preparation route of MXene has been basically established,laying a foundation for subsequent work.Multilayer Ti₃C₂T_x,prepared by hydrofluoric acid etching,was directly used as a catalyst for the conversion reaction of biomass—5-hydroxymethylfurfural?HMF?,in order to obtain high value-added organic monomer 2,5-furandicarboxylic acid?FDCA?.The application of MXene materials in biomass conversion was explored.As a result,it was found that Ti₃C₂T_x did have a certain reactivity,and 40% of HMF was converted in 8 hours.Further,the noble metal Pt nanoparticles were loaded on the multilayer Ti₃C₂T_x by refluxing method,to improve catalytic performance.The results showed that Pt/Ti₃C₂T_x could obtain good catalytic performance with a Pt loading of 2 wt% under mild conditions.Complete conversion of HMF and FDCA selectivity of up to 98.95%were achieved.The preparation process of MXene material was further expanded.The thin layer of Mo-based MXene?Mo₂CT_x,Mo₂Ti₂C₃T_x? were successfully prepared by hydrofluoric acid etching and organic molecular-assisted delamination,and its electrochemical activity was further explored.It was found that Mo-based MXene have a certain reaction activity in hydrogen evolution reaction.The results showed that the Mo₂CT_x had an overpotential of 290 mV at a current density of 10 mA/cm²,while the overpotential of Mo₂Ti₂C₃T_x was 318 mV.The activity can be further improved by annealing and doping.These materials open up new routes for the design of water splitting catalysts.