ZIF Template Method To Construct Co, Fe Bimetallic Catalyst And Its Oxygen Reaction Performance Research

As an important primary energy source of fossil fuels,its massive combustion not only causes global climate change,but also seriously disrupts the ecological balance.Therefore,it is urgent to develop and utilize renewable new energy.Among various new energy storage and conversion devices,rechargeable zinc-air batteries and water splitting devices have the advantages of high safety and good environmental compatibility.The slow kinetic process of oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?is an important factor that restricts the performance of these devices,so it is indispensable to design an efficient electrocatalyst to accelerate the reaction process.So far,precious metal-based materials such as Pt,Ir and Ru O₂ have been considered as the most effective catalysts for ORR or OER.However,due to its high price,limited resource reserves and lack of durability,the large-scale application of these precious metal materials in energy storage technique is hindered,so it is necessary to develop high-performance non-precious metal-based catalysts to replace precious metals.In this thesis,ZIF is used as a template to synthesize Co and Fe-based catalysts,the catalytic activity,durability and practical application of OER/ORR were evaluated.The main research contents of this thesis are as follows:Cubic ZIF-67 was synthesized under water system;Fe²⁺was introduced by ion-exchange to form a Co Fe-ZIF precursor,which was carbonized to obtain Co Fe/NC catalyst.Co Fe/NC-0.2-900 has the best ORR performance(E_onset=0.94 V,J_lim=6.4 m A cm^-2),and the performance has almost no attenuation after 10 000 cycles.The rechargeable zinc-air battery has low potential difference between charge and discharge,high power density and excellent cycling stability.Hexagonal Zn O was used as a self-sacrificial template and coordinate with 2-methylimidazole to form the core shell structure of Zn O@ZIF-8.After high temperature carbonization treatment,hollow carbon materials were formed.As its surface is rich in nitrogen element,it can be used as an effective host for Fe ion adsorption.It is pyrolyzed in N₂ atmosphere to form Fe-N-HC catalyst.Fe-N-HC-2 has the best ORR performance(E_onset=0.98 V,E_1/2=0.85 V,J_lim=5.6 m A cm^-2),assembled a zinc-air battery with a power density of 167.0 m W cm^-2 and withstood the 190h long cycle test.Co-LDH nanosheets were synthesized by hydrothermal method.After adding 2-methylimidazole as a ligand,ZIF-67 nanoparticles were grown in situ in Co-LDH,and Co₃O₄/NF nanosheets were obtained after low-temperature oxidation.At a current density of 10 m A cm^-2,the OER potential of the Co₃O₄/NF-5 catalyst is 1.52 V.The output current density of 10 m A cm^-2 can be achieved in a water splitting device with a voltage of only1.60 V.