Application Of Metal-organic Framework In Hydrogen Evolution Reaction,Oxygen Evolution Reaction And Supercapacitors

Metal organic framework(MOF)material not only has a larger specific surface area and excellent porosity,but also has rich metal centre and carbon source.Then MOF can be used as a template to prepare porous carbon and metal/metal oxide.Therefore,MOF are widely used in the field of electrochemistry.In this paper,a series of MOFs and their derived materials were prepared and their applications in hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and supercapacitors were studied in detail.The work includes the following four parts:1.Carbon coated nickel-nickel oxide composites Ni/NiO@C/GR was synthesized from the direct carbonization of the composites Ni-MOF-GO composed of Ni-MOF-74 and graphene oxide(GO).The electrocatalytic properties toward HER and OER were studied by linear sweep voltammetry(LSV),cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The experimental results showed that Ni/NiO@C/GR exhibit higher electrocatalytic activity for HER compared with Ni-MOF-GO.Especially in acidic medium,when the GO content was 8%and the carbonization temperature was 900?,the composites Ni/NiO@C/GR-900-8 showed the best electrocatalytic properties for HER with a smaller Tafel slope of 44 mV/dec and an lower overpotential of 108 mV at 10 mA/cm2.The excellent electrocatalytic performance enabled Ni/NiO@C/GR composites to be a favorable HER catalyst to replace the expensive Pt-based materials in the applications of the hydrogen production.Meanwhile,Ni/NiO@C/GR-900-8 displayed good electrocatalytic activity toward for OER.2.A series of porous carbon materials A-C-MOF-t were prepared at different carbonization temperatures using Co-MOF-74 as a template,and its double-layer capacitance properties were studied by EIS,CV and chronopotentiometry(CP).The experimental results showed that carbonization temperature had an important effect on the specific surface area,pore structure and capacitance performance of porous carbon materials.When the carbonization temperature was 800?,the porous carbon material A-C-MOF-800 had the most excellent capacitance performance of 188 F/g at a current density of 0.1 A/g.Besides,95.7%capacitance was still retained after 4000 cycles at a current density of 1 A/g.3.4,4'-Bipyridyl and L-malic acid as organic ligands and Ni2+ as metal centers,the Ni-MOF with the plane network structure was synthesized by the solvent thermal method.Based on this,a series of composite materials Ni-MOF/CNT were prepared by introducing carbon nanotubes(CNT)with large specific surface area and excellent conductivity.EIS,CV and CP were used to study the capacitive properties of the prepared materials.The experimental results showed that the composite Ni-MOF/CNT had the excellent capacitance.When CNT content was 10%,Ni-MOF/CNT(10%)exhibited the best capacitance performance of 1133 F/g at a current density of 2 A/g.Moreover,78.6%capacitance still retained after 4000 cycles.4.In order to further improve the capacitance of Ni-MOF,Co was introduced into Ni-MOF and the new material Ni/Co-MOF was synthesized.The results showed that the capacitance performance of Ni/Co-MOF is significantly improved compared to Ni-MOF.In addition,the content of Co significantly affected the capacitance performance of Ni/Co-MOF.When the molar ratio of Ni/Co is 1:1,Nil/Col-MOF has the highest specific capacitance of 1333 F/g at a current density of 2 A/g.In addition,78.7%capaciyance still retained after 4000 cycles.