Design,Synthesis And Electrocatalytic Performance Of Porphyrin-Based Supramolecules And Their Derivatives

The extensive use of traditional fossil fuels has brought energy crises and serious environmental pollution problems to human development.Therefore,the development of renewable and clean energy has become urgent.As a promising new power source,fuel cells are widely used in various fields.For the hydrogen electrode in a fuel cell,the kinetics of the reaction occurring on the cathode is slow,and a highly active catalyst is required to promote the reaction.Although commercial Pt/C catalysts have excellent oxygen reduction performance,they are scarce and expensive.Therefore,the development of platinum-free catalysts is a current research focus.In this thesis,starting from the design and synthesis of metalloporphyrin-based supramolecular materials,the porphyrin-based supramolecular precursors were successfully prepared.After heat treatment,different derivative composite electrocatalytic materials were obtained.Finally,the structure and morphology of these electrocatalytic materials were characterized and their electrochemical properties were studied.The main research contents are as follows:（1）Synthesis and ORR performance studies of electrocatalytic material Ni/Ni O@CN-1.The supramolecular crystal UPC-S7 was synthesized from 5,10,15,20-tetra（4-cyanophenyl）porphyrin and nickel nitrate hexahydrate in N,N-Dimethylacetamide at 90℃for 72 hours.Ni@CN was obtained by carbonizing UPC-S7 precursor under nitrogen atmosphere,and then Ni/Ni O@NC was obtained by partially oxidation of Ni@CN in air at low temperature.Subsequently,Ni/Ni O@CN-1 was obtained by soaking Ni/Ni O@NC in a certain concentration of nitric acid and ammonia.The material has excellent oxygen reduction performance.ORR test in 0.1 M KOH solution under 1600 rpm shows that the limiting current can reach-5.49m A·cm^-2,which is equivalent to the commercial 20%Pt/C and has better stability.（2）Preparation and oxygen reduction performance of electrocatalytic material Fe/Fe₃C@CN-800_4:1.The supramolecular crystal UPC-S8 was synthesized by solvothermal method using 5,10,15,20-tetra（4-cyanophenyl）porphyrin and ferrous chloride tetrahydrate as precursors.Firstly,UPC-S8 and g-C₃N₄ were physically compounded at different mass ratios with ethylene glycol as binder in nitrogen atmosphere at 250°C,and then the composite was carbonized at high temperature to obtain Fe/Fe₃C@CN-800 Series of electrocatalytic materials.The oxygen reduction ability,stability and methanol resistance of the products were tested,and the results show that when the mass ratio of g-C₃N₄ to UPC-S8 is 4:1,the electrocatalytic material has excellent electrocatalytic oxygen reduction performance due to its large specific surface area,multiple active sites such as Fe₃C and Fe.The onset potential is 0.95 V,the half-wave potential is 0.84 V,and the limiting current is-5.48 m A·cm^-2.（3）Preparation and and its oxygen reduction performance of electrocatalytic material Co@NC-800.Supramolecular crystal UPC-S9 was prepared by solvothermal reaction using5,10,15,20-tetra（4-cyanophenyl）porphyrin and cobalt nitrate dihydrate as precursors,and the Co@NC-800 series electrocatalytic materials were further obtained by direct carbonization of UPC-S9.The oxygen reduction ability of products with different carbonization temperatures was tested.The results show that the electrocatalytic material Co@NC-800 obtained under 800℃has best electrochemical performance,and the onset potential of Co@NC-800 is 0.90V,which is close to the value of commercial Pt/C.At a current density of 10 m A·cm^-2,the oxygen evolution performance test shows an overpotential of 416 m V.These results indicate that the catalyst has both oxygen reduction and oxygen evolution properties,and is a bifunctional catalyst.