The Study On The Preparetion And Performance Of N-doped Porous Carbons Derived From Metal Organic Coordination Polymer

As a new type of energy storage and transmission device,supercapacitor has been widely used in many fields due to its high power density,long cycle life and fast charging/discharging rates.The electrode material is the key factor to determine the performance of the supercapacitor.Currently,porous carbon materials have attracted widespread attention due to their good electrical conductivity,large specific surface area and good chemical stability.However,the porous carbons without heteroatom doped always suffered relatively low gravimetric specific capacitance because of the limited specific surface area.Meanwhile,the packing density of porous carbon is relatively low,resulting in lower volumetric specific capacitance,which largely limits its practical application.Recently,N-doping has been regarded as an effectively strategy to enhance electrochemical performance of carbon electrode materials,as N could provide pseudocapacitance and improve the electrical conductivity and wettability.It is therefore becomes a hot spot in the research of supercapacitor electrode materials.Herein,biligand metal organic coordination polymers?MOCPs?,metal organic coordination polymers/metal organic framework composites and bimetallic organic coordination polymers were used as precursors to prepare different N-doped porous carbons?NPCs?with high electrochemical performance,the main research contents are as follows:?1?One of the different molecular structures of aromatic amine ligands?p-phenylenediamine?PPD?,4,4'-diaminobiphenyl?AMP?and 3,3'-diaminobenzidine?DAB??and the ligand?4,4,-bipyridine?BPD??with different metal ions were performed a double coordination reaction.The obtained biligand metal-organic coordination polymers?[Co3?BPD?7?PPD?10Cl6]n,[Ni?BPD??AMP?3Cl2].and[Co3?BPD?:?DAB?SC16]n?are employed as nitrogen contained precursors and directly carbonized to form controllable microstructures and different high nitrogen content NPCs materials,BPCce?11.39 at.%?,BAC_Ni?8.26 at.%?and BDCce?9.94 at.%?.The as-prepared BPC_co,BACNI and BDCce possess high gravimetric specific capacitance of 402,315.5 and 302.5 F g^-1 and volumetric specific capacitances of 494.5,306.0 and 465.7 F cm^-3,respectively.Furthermore,the BPC_co,BAC_Ni and BDC_Co assembled symmetric supercapacitors show outstanding energy density of 16.50,13.38 and 12.98 W h kg^-1,respectively.Our strategy paves a new avenue to produce high performance NPCs with controllable structure,nitrogen species and contents through rational design of organic molecule structures in MOCP precursors.?2?4,4'-bipyridine?BPD?and 2-methylimidazole?Melm?with metal ions(Co²⁺)were performed a coordination reaction.The obtained MOF-MOCP composite was employed as N-containing precursors and directly carbonized to prepare NPC.As comparison,we also prepared the nitrogen doped porous carbon by directly carbonizing MOF and MOCP in the same condition,respectively.The density of as-prepared BCCo,MCCo and BMCCo are 0.82,1.12,1.16,the N-doped content can reach 10.86,11.13,11.63 at.%.When used as electrodes material for supercapacitors and exhibits excellent electrochemical properties.In three electrode cell,the BCCo,MCco and BMCco show high gravimetric specific capacitance of 258.1,212 and 393.9 F g^-1,volumetric specific capacitances of 211.6,237.4 and 456.9 F cm^-3 at current density of 0.5 A g^-1,respectively.After 5000 cycle at high current density of 20 A g^-1,the gravimetric specific capacitance still can maintain initial value of 100,100 and 102.4%,respectively.Additionly,the BCCo,MCCo and BMCco assembled symmetric supercapacitors in 1 M H2SO4 electrolyte show outstanding energy density of 16.23,9.89 and 23.32 W h kg^-1,respectively.Besides,BMCCo assembled symmetric supercapacitors in 1 M Na2SO4 neutral electrolyte exhibit high energy density of 29.74 W h kg^-1.As-prepared NPC show excellent electrochemical performances and has a very broad application prospect as electrode material for supercapacitors.?3?P-phenylenediamine?PPD?and two types of metal ions(Zn²⁺ and Co²⁺)were performed a coordination reaction,and the obtained bimetallic MOCP?[Co?PPD?₄Zn]_n?used as precursor by carbonization to prepare nitrogen doped porous carbon.Using high nitrogen content of PPD as organic ligand,it can also be used as nitrogen source and carbon source.When the current density is 0.5 A g^-1,the specific capacitance is 422.6 F g^-1,and when the current density is 20 A g^-1,the specific capacitance still possesses 192.6 F g^-1,which showing a good rate performance.Furthermore,after 3000 cycle at high current density of 20 A g^-1,the gravimetric specific capacitance still can maintain initial value of 104.3%,showing excellent cycling stability.The reasonable design of the molecular structure of bimetallic MOCP provides a new approach for the preparation of high performance of NPC.