Preparation Of ZnCo-MOF-derived Carbon-based Catalysts And Their Applications

Rechargeable Zn-Air Batteries（ZABs）is regared full of promise next-generation energy conversion device owe to it’s high specific energy density,low cost and high safety.But,the slow kinetics and poor electrochemical stability of air cathode materials have largely hindered their commercialization,resulting in unsatisfactory rechargeability and low energy conversion efficiency.Now,the matel Pt and Ru/Ir oxide catalysts have been developed for oxygen reduction reactions（ORR）and oxygen evolution reactions（OER）,respectively.Regrettably,the expensive cost and restricted provide of these precious metal-based catalysts hindered the large-scale commercialization of ZABs.Therefore,the development of earth-rich and cost-effective precious metal electrocatalysts with excellent dual-function performance is very necessary to promote the commercialization of rechargeable ZABs.Therefore,this thesis designs a simple method to synthesize non-precious metal porous carbon materials for Zn-air batteries.Mainly did two studies:（1）Successfully prepared a Fe-Co-hollow porous nanocarbon material derived from Fe-modified bimetallic zeolitic-imidazole frameworks（ZIFs）is demonstrated.Owing to the unique 3-dimensional interconnected hollow porous carbon structure of the developed material and the synergetic effect of the corresponding bimetallic system,it shows good bifunctional oxygen electrocatalytic properties.Compare to the commercial 20%Pt/C and Ir O₂or Ru O₂,the half-wave potential of oxygen reduction reaction（ORR）of the developed catalyst reaches 0.81 V（Pt/C is 0.84 V）,and the overpotential of oxygen evolution reaction（OER）at 10 m A/cm²current density is0.43 V（the overpotential of Ru O₂of 0.4 V）.When the rechargeable liquid Zn-air batteries are assembled with the Fe-Co-N-PC catalysts as the cathode,it shows a power density of 100.2 m W/cm²and cycling stability of 2500 min,which are better compare to the commercial Pt/C-Ru O₂（the power density and cycling stability of Pt/C-Ru O₂is 99.2 m W/cm²and cycling stability of 2200min,respectively）.In addition,the open-circuit potential（OCP）of the produced rechargeable liquid and flexible solid-state ZABs reach up to 1.47 V and 1.45 V,respectively;also,the material exhibits good bending flexibility and stability.Overall,this development provides a new method for solid-state ZABs systems of MOF-derived carbon materials.（2）The metal-organic framework（MOF）is used as non-precious metal catalyst because of controllable,high surface area and rich N content.But considering that it will shrink due to high temperature during the carbonization process.Herein,MOF transformed into three-dimensional and porous Co-N-C catalyst by a one-step synthesis method and the joint action of Zn and PVP is reported.The catalyst exhibits efficient oxygen reduction reaction（ORR）performance(E_1/2=0.83 V)and oxygen evolution reaction（OER）performance(E_j10=1.65 V).More meaningfully,the Zn-air batteries（ZABs）assembled with the Co-N-C catalyst,exhibiting superior 3100 min cycling charging/discharging stability and high power density of 109.8 m W/cm²,compared with the Pt-Ru O₂of 2600 min of cycling charging/discharging stability and power density of 96.1 m W/cm².what is more,the solid-state ZABs based on the Co-N-C catalyst shows excellent rechargeable flexible and stability.Undoubtedly,this work designs a bifunctional oxygen electrocatalytic catalyst of the practical application value.In this thesis,Zn Co-MOF is used as precursors,and carbon material catalysts formed by introducing different metals Zn,Co,and Fe are used to achieve the purpose of improving catalytic activity and realizing multi-functionality.The prepared catalysts not only possess good multifunctionality,but also have excellent battery performance in liquid and solid-state zinc-air batteries.Through different chemical characterization methods and performance tests,the effects of different factors on the performance of the catalysts were studied,which provides a new idea for the research of Zn-air batteries.Figure 30 table 6 reference 150...