| Metal organic frameworks(MOFs)are a kind of novelty crystalline porous materials formed by coordination self-assembly of the organic ligands contained O or other heteroatoms and metal ions(clusters).Due to their particular advantages,such as big specific surface area,regular and ordered channel structure and designable structure and function,MOFs materials have widely been applied in separation,adsorption,sensing,energy storage,gas storage and so on.Because the conjugated organic monomers ensure efficient charge transfer and the metal ions(clusters)provide redox active centers,the resulted MOFs have become excellent substitutes for traditional electrode materials.Using them as electrode materials can effectively make up for the deficiencies of the traditional capacitor including low specific capacitance and poor cyclic stability.In this thesis,influence of heteroatom doping on the electrochemical performances of MOFs and the derived carbon materials have been dtudied in detail,some excellent MOFs composition materials have prepared and their electrochemical properties have been investigated.The thesis consists of three parts as follows:(1)A new MOFs material with loose lamellar structure was prepared using N-containing conjugated organic ligand,which was obtained through Schiff base reaction using a simple hydrothermal method,and then the resulted nitrogen-rich porous carbon materials containing metal oxide were obtained by direct carbonization at different temperatures.It was found that both of the obtained MOFs materials possessed good electrochemical properties and at a current density of 0.5 A·g-1,specific capacitance were respectively 670 F·g-1 and 1850 F·g-1.At the same time,the prepared porous carbon material MOF-B-600 at 600?not only kept pore characteristics of the precursor,but also remarkably enhanced specific surface area(from 61.5 to 209.9 m2·g-1)and increased underpotential deposition sites,so that its pseudocapacitive property was further improved.At the current density of 1.0 A·g-1,the carbon material showed the biggest specific capacitance of 2727.5 F·g-1 and high capacitive rention rate of 83.33%after 10000 cycles.In addition,in two-electrode system,high power density 800 W·kg-1 and energy density 41.78 Wh·kg-1 were obtained too.(2)During the hydrothermal synthesis of MOFs,the solvent molecules always participate in coordination with the metal ions.But the solvent removal necessarily results in insufficient metal coordination and resulting crystal defects.And these defects will reduce the structure stability and its application performance.In this chapter,different heteroatoms such as N,P and S were introduced into Ni-MOF to make up to these defects,enhance its stability and improve its electrochemical properties.The results showed that the non-metal modification for N-MOF indeed made up for the crystal defects effectively,increased underpotential deposition sites and improved Faradaic response.Especially,the obtained S@Ni-MOF showed the highest specific capacitance and the optimal cyclic stability.At 1.0 A·g-1 the specifc capacitance was 1453.5 F·g-1 and the capacitance loss was only 10.77%after 5000cycles.Using it as electrode material the fabricated all-solid state asymmetric supercapacitor also exhibited a high energy density of 56.85 Wh·kg-1 and a high capacitive rentention of 86.67%after 20000 cycles.(3)At first an accordion speaker-like lamellar structure Ni-MOF was prepared using Ni(NO3)2.6H2O and 1,4-dicarboxybenzene as raw materials,and then through a hydrothermal treatment of the Ni-MOF in the presence of Na2Mo O4·2H2O and thiocarbamide,a Ni-MOF coated Mo S2 nanoflower core-shell-like structure was obtained.This structure displayed excellent electrochemical performances and at the current density of 1.0 A·g-1,the highest specific capacitance was 1590.24 F·g-1,which was 27.64 times as that of Mo S2 and 2.84 times as that of the Ni-MOF,respectively.Moreover,the prepared asymmetric supercapacitor Mo S2@Ni-MOF//AC possessed a good energy storage property and high cyclic stability.The energy density was 72.93Wh·kg-1 at the power density of 375 W·kg-1,and the capacitance rentention rate was94.61%of the initial value after 10000 cycles.These results suggested the obtained material has a very good application potential. |
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