| As a new type of crystalline material,Coordination Polymers(CPs)are self-assembled by metal centers and organic ligands through coordination bonds.CPs combine the advantages of organic and inorganic materials,such as adjustable structure and composition,porosity,as well as inherently hybrid properties.They have been extensively studied in the fields of optics,electricity,magnetism,catalysis and so on.Compared with other porous materials,CPs-based materials are expected to replace Pt-based materials as highly active ORR electrocatalysts.The main works of this thesis are as following:1.Three CoII-based CPs were synthesized using nitrogen-rich ligands:3,5-bis[(2-pyridyl-2-methoxyl-methyl)-amino]-1,2,4-triazole(Hpmmat)and4,5-bis(1H-tetrazol-5-yl)-2H-1,2,3-triazole(H3dttz),namely,[Co(pmmat)Cl O4]2(1)?[Co(Hdttz)(2,2'-bipy)]3·2H2O(2)and[Co(Hdttz)(phen)]4(3)(2,2'-bipy=2,2'-Dipyridyl,phen=1,10-Phenanthroline monohydrate).Single crystal X-ray diffraction and XPS show that CPs 1-3 all have zero-dimensional cluster structures.They show binuclear,trinuclear and tetranuclear structures,respectively,containing pyridine-N and triazolyl-N with{Co NxOx}catalytic active sites.The studies of ORR electrocatalytic performance indicate that the activity of CPs 1 and 3 are almost equivalent to that of 20%Pt/C,whose onset potential(Eonset)is 1.10 V,half-wave potential(E1/2)is 0.93 V and limiting current density(JL)is 4.74 m A/cm2.The JL of CP 1 as an ORR electrocatalyst is 4.43 m A/cm2,the Eonset and E1/2 are 1.05 V and0.79 V,respectively.The ORR process of CP 1 is a 4e-transfer process and shows higher stability than Pt/C.The zinc-air batteries of CPs 2-3 as the cathode material have high open circuit potentials,and the maximum power densities are 107.28m W/cm2 and 95.16 m W/cm2,respectively.They have high specific capacities at the current density of 5 m A/cm2,which are 670 m Ah/g and 780 m Ah/g,respectively.The zinc-air batteries aslo exhibit excellent charge-discharge cycling stability at different current densities.In addition,two zinc-air batteries connected in series can successfully light up 2 to 2.2 V LED lamps for more than 72 hours.2.Three high-dimensional CPs were synthesized using nitrogen-rich ligands H3dttz,that are,[Co(Hdttz)(Me OH)]n(4)?[Fe?(Hdttz)(2,2'-bipy)](5)and[Fe?(Hdttz)(phen)](6).Single crystal X-ray diffraction shows that CP 4 is a two-dimensional network structure connected by dinuclear cluster units{Co2N8O2}and Hdttz2-.CPs 5-6 have similar 1D chain structures connected by two adjacent Fe?.CPs 4-5 show good ORR electrocatalytic activity and follow nearly 4e-transfer processes.Using CP 4 as the cathode material of zinc-air battery,the maximum power density reaches to 99.9 m W/cm2.The discharge can last for 58 hours at a current density of 10 m A/cm2,and the corresponding specific capacity is as high as805 m Ah/g.The battery also shows excellent long-term charge-discharge cycling stability at different current densities.The ORR electrocatalytic process of CP 6 is a mixed process of 2e-and 4e-.As a cathode material for a zinc-air battery,it also displays good cycling stability until 120 h at a current density of 5 m A/cm2.3.A new Fe-MOF[Fe3(BTC)2(H2O)1.5]1.5 H2O(7)was synthesized based on ligand H3BTC.When pyrolysis thiourea@Fe-MOF precursor at different temperatures,four Fe-MOF derived materials were obtained.Among them,honeycomb-like N,S-dual doped carbon composite(abbr.Fe S/Fe3C@NS-C-900)obtained at 900?exhibit good ORR/OER bifunctional electrocatalytic activity,whose potential gap(?E)is only 0.72 V.As the cathode material of a rechargeable zinc-air battery,its maximum power density is 90.9 m W/cm2,and the specific capacity is as high as 750 m Ah/g.It can be cyclically charged and discharged for more than 865 h(1730 cycles)at a current density of 2 m A/cm2.In addition,two zinc-air batteries connected in series can light up a 2.4 V LED light. |
PDF Full Text Request