Tow-dimensional Materal:V₂CT_Z And Porous V₂CT_z

Recently, the novel two-dimensional (2D) materials such as graphene, and early transition metal carbides or carbonitrides (MXenes) possessing distinctive properties have attracted tremendous attention. MXenes are usually derived by the selective exfoliation of aluminium from MAX phases with the treatment by hydrofluoric acid.[2To date, quite plenty of MXenes have been synthesized with the general formula by Mn+1XnTz(M is the early transition metal, X is C and/or N, n is1,2,3, and Tz stand for terminated groups like O2-, OH-and/or F-groups), such as Ti2CTz, V2CTz, Nb2CTz,(Ti0.5, Nb0.5)2CTz, Ti3C2Tz,(V0.5, Cr0.5)3C2Tz, Ta4Tz and Nb4C3Tz.They usually have the unique specific surface area, excellent electronic conductivity and good hydrophilic property. Hence, MXenes have been poved to be the promising material candidates for lithium (Li)-ion batteries, supercapacitors, fuel cells and so on. In this paper,V2CTZ and porous V2CTZ are synthesized and characterized.Besides,we research on the porous structure inside V2CTZ can effectively influence the charging rate of V2CTZ electrode, which has the potential as the supercapacitors. The main content of this thesis is:(1)(V1-xCrx)2AlC (x=0,0.01,0.05,0.10,0.15) was sintered by SPS using raw mater ials of V, Cr, Al, C.The results of XRD and SEM characteristic can estimate the effect s of temperature on purity of V2AlCand (V1-Crx)2AlC (x=0,0.01,0.05,0.10,0.15). According to these datas,we finded out the optimum sintering temperature is1500℃、1500℃、1475℃、1475℃、1450℃。(2)we have developed a robust strategy of one-step synthesis to obtain V2CT2; and porous V2CTZ from (V1-xCx)2AlC solid solution (x=0,0.01,0.05,0.10,0.15) by the treatment of40wt.%hydrofluoric acid at room temperature. The latter not only can etch aluminum atoms but also can corrode chromium atoms, which lead the pores formed on the plain MXene flakes.(3)The pore size of the powders immersed for1d,3d,5d and7d are about45nm,60nm,100nm and190nm, respectively, which are controlled well by the immersing time and Cr-doped content.(4) At high scan rate, the porous V2CTz-based supercapacitors exhibit more outstanding specific capacitance than plain V2CTz-based supercapacitors. The reason is that the pores can shorten the distance of K+ions diffusion, which makes more K+ions adsorbed on electrode when the charge-discharge time is finite.