Preparation And Characterization Of Nickel-based Metal Organic Framework/polymer Composite Film

Environmental pollution and energy crisis are two major problems facing mankind at present,and the development of new energy conversion technology and new energy storage materials can fundamentally solve these problems.So in recent years,many researchers have put into the exploration of energy conversion and storage technology and made good achievements,such as proton exchange membrane fuel cells,supercapacitors and so on have been widely used.For proton exchange membrane fuel cells and supercapacitors,proton exchange membrane and electrode materials as their respective core components,their quality determines the performance of the device itself.Therefore,it is the focus of researchers to find proton exchange membrane materials and electrode materials with good performance and low price.Organometallic frame materials?MOFs?because of its advantages of adjustable pore size,high specific surface area and high porosity,many reports have shown that it has remarkable electrochemical properties in supercapacitor electrode materials and has some potential in proton exchange membrane applications.In this paper,the composite films with different morphology were prepared by solution casting and direct current high voltage electrospinning using metal organic framework compounds as precursors and hybridized with polymer materials.The microstructure of the sample was characterized by scanning electron microscope?SEM?,Raman spectra?Raman?,powder X-ray diffraction?PXRD?,X-ray photoelectron spectroscopy?XPS?,transmission electron microscope?TEM?,thermogravimetric analysis?TGA?,element mapping measurements?Mapping?,Energy-dispersive elemental analysis?EDS?,and the proton conductivity of the sample as a proton exchange membrane at different temperatures and humidity,as well as the electrochemical properties of electrode materials for supercapacitors.The main research contents are as follows:?1?Preparation and characterization of 2D Ni-BDC coordination polymersUsing Ni²⁺as metal cation and 1,4-benzenedicarboxylic acid as organic ligand,Ni-BDC coordination polymer was synthesized in glass tube by diffusion method.Ni-BDC crystals were successfully synthesized by powder PXRD.The results of SEM and TEM tests showed that Ni-BDC had ultrathin nanosheet morphology.?2?Preparation and characterization of H₃PO₄@Ni-BDC/PAN composite membraneNi-BDC/PAN membrane was prepared by solution casting.The XRD patterns of the composite membrane are mainly Ni-BDC characteristic diffraction.Electron microscopy showed that Ni-BDC particles were uniformly embedded PAN the matrix.the Ni-BDC/PAN membrane was immersed in H₃PO₄ solution with a concentration of85%?30?3 days and 60?4 hours?for acidification treatment to obtain a proton conductive H₃PO₄@Ni-BDC/PAN composite membrane.The powder X ray diffr-action showed that H₃PO₄ treatment did not change the crystal structure of the Ni-BDC/PAN membrane.The distribution of elements on the surface of H₃PO₄@Ni-BDC/PAN membrane was studied by means of X-ray photoelectron spectroscopy?XPS?.Thermal stability of H₃PO₄@Ni-BDC/PAN composite memb-rane was analyzed by thermogravimetric analysis?TGA?.The conductivity of the H₃PO₄@Ni-BDC/PAN composite membrane was tested,and it was found that the proton conductivity was up to 1.05×10^-2 S cm^-1 at a temperature of 353 K 90%rela-tive humidity?RH?.The mechanism of proton conduction in composite membrane was studied.?3?Preparation and characterization of imidazole@Ni-BDC/PAN fiber membraneNi-BDC/PAN fiber membranes were prepared by electrospinning.Electron microscopy revealed that Ni-BDC particles were successfully introduced into PAN fibers,and the particles were uniformly dispersed in the matrix without obvious agglomeration.The Mapping,electron EDS showed that the C?O?N and Ni were uniformly distributed in each fiber.Ni-BDC/PAN fiber membrane was vacuum dried and imidazole was evaporated into the Ni-BDC/PAN membrane.The presence of imidazole in the Ni-BDC/PAN fibers,without reactions and conversion,was confirmed by TGA.The proton conductivity of the membrane was increased by the addition of imidazole,which was 6.04×10^-5 S cm^-1 under the condition of temperature 363 K and 90%relative humidity?RH?.The proton conduction relaxation process in one-dimensional nanofibers was studied.?4?Synthesis and characterization of Ni-CNFs composite fibersThe electrospinning Ni-BDC/PAN fiber film was carbonized at high temperature to obtain Ni-CNFS composite fiber,which was used as electrode material for supercapacitor without adhesive.Three-electrode electrochemical measurements were used in 6 M KOH electrolyte,and the electrode showed high specific capacitance(672 F g^-1)at a current of 2 A g^-1,tested in a three-electrode system electrolyte and has good rate performance,there is a specific capacitance of 385 F g^-1 at the current den-sity of 10 A g^-1,reaching a capacitance retention of 57%.Furthermore,at high current density(20 A g^-1),the capacitance retention rate reached 75.8%after 1000 charge/discharge cycles.Finally,the binder-free nanofibers were assembled into symmetrical supercapacitors with an energy density of up to 17.8 Wh kg^-1 at a power density of350 W kg^-1.The energy density remains as high as 3.67 Wh kg^-1.The synergistic effect of electrochemical reaction in composite fibers was studied.