The Application Of Porous Carbon Matrials Derived From MOFs On Supercapacitors

With the development of the economic,there is an increasing demand of energy sources.Supercapacitors as a kind of new original energy storage elements,superior to the secondary battery and general capacitor performance,have been extensively studied.The electrode material is the key factor,which determining the performance of a supercapacitor.The porous carbon material with the advantages of the excellent electrical performance,the rich pore structure and large specific surface area,is the priority of electrode material.In this dissertation,several porous carbon materials derived from the metal organic frameworks?MOFs?were prepared and their applications on supercapacitor were studied.Furthermore,the influence of the template structure,pore structure,specific surface area,the doped oxide and atoms on supercapacitor performance was discussed in detail.?1?MOF-74,one of the MOFs,is composed of Zn²⁺ions bridged by the carboxylate and hydroxyl groups of fully deprotonated 2,5-dihydroxybenzene-1,4-dicarboxylic acid,arranging in a parallel,hexagonal manner.In the second chapter,a series of porous carbon material based on Zn-MOF-74 were prepared.The pore structures and its formation were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?and N₂ adsorption-desorption experiments.The effect of pore structure on supercapacitor performance was analysis by electrochemistry methods.The results show that the materials have layered pore structure with micropores,mesopores and macropores.The carbonization temperature has a key influence on the structure of the porous material.The specific surface areas range from 7.028 m²·g^-1 to 900.4 m²·g^-1.The specific capacitance reaches the maximum of187 F·g^-1 which is superior to the reported ones.?2?In the third chapter,pure porous carbon materials?A-C-Zn-MOF-H₂pdc-n?and the composites of porous carbon and ZnO?W-C-Zn-MOF-H₂pdc-n?were prepared based on Zn-MOF-H₂pdc?H₂pdc=2,5-pyridinedicarboxylic acid?which has 3D pore structure.The results show that the pore structure of the template and the hetero atom in template also have a significant influence on the pore structure of the purpose materials besides the carbonization temperature.All A-C-Zn-MOF-H₂pdc-n have both mesoporous and macroporous structure and their specific surface areas rangefrom272.3to931.8m²·g^-1.Thespecificcapacitanceof A-C-Zn-MOF-H₂pdc-700 can reach as high as 140 F·g^-1.However,the pore structure of W-C-Zn-MOF-H₂pdc-n containing zinc oxide differs from A-C-Zn-MOF-H₂pdc-n.Moreover,the specific capacity of W-C-Zn-MOF-H₂pdc-n is largely different because the proportions of zinc oxide in composites are different at the different carbonization temperature.?3?Zn-MOF-5 consists of metal clusters[Zn₄O?CO₂?₆]?as the corners of the unit cells?joined by benzene dicarboxylate linkers to form an another extended 3D simple cubic topology with intersecting pores with a 8?aperture width and a 12?pore diameter²?They are pseudospheres within the intersection of three mutually orthogonal pore channels?.In the forth chapter pure porous carbon materials?A-C-Zn-MOF-5-n?and the composites of porous carbon and ZnO?W-C-Zn-MOF-5-n?were prepared based on Zn-MOF-5.The results show that A-C-Zn-MOF-5-n has structures of microporous,mesoporous and macroporous.Their specific surface areas range from 598.9m²·g^-1 to 968.2 m²·g^-1.The specific capacity of pure porous carbon can reach as high as 158 F·g^-1,which is superior than A-C-Zn-MOF-H₂pdc-n.Moreover,W-C-Zn-MOF-5-n has a wider potential window in comparation with the literature.This ensures W-C-Zn-MOF-5-n a high specific capacity(748 F·g^-1).The electrochemicial performance is better than W-C-Zn-MOF-H₂pdc-n.As a conclusion,1D template results in the good pore structure and can prevent the formation of closed pores which caused by structure collapse during carbonization.However,it has the lower specific area.The 3D structure of Zn-MOF-H₂pdc is good for the formation of high specific area,especially when doped with ZnO.The specific surface area of W-C-Zn-MOF-H₂pdc can reach as maximum as 1518.9 m²·g^-1.But their specific capacity is limited because this 3D structure causes the formation of closed pores during the carbonization process.Zn-MOF-5 with another type of 3D structure has the good rigidity and two types of the pore channel structure,which benefit for the formation of complex pore structure.This not only ensures a higher specific surface area,but also benefits for the electron conduction during charge-discharge process.It is the best template among the three listed templates.