Preparation And Performance Research Of Oxygen Reduction Reaction Of Iron-based Electrocatalysts Derived From Mixed Linkers MOF

In recent years,as a vital reaction of oxygen reduction reaction(ORR)in fuel cells and other energy devices,the oxygen reduction reaction kinetics are slow,which greatly limits the large-scale application of ORR devices.Even though the precious metal electrocatalysts such as Pt,Pd and their alloys have been commercialized that can meet the US Department of Energy's application targets,the disadvantages of high cost and rare reserves hinder the large-scale promotion of precious metal ORR catalysts.Therefore,the development of non-precious metal ORR electrocatalysts with low cost,high abundance,great performance and excellent stability is of great significance for theirs application.Zeolitic Imidazolate Framework(ZIF),one of the Metal Organic Framework(MOF),has attracted widespread attention due to pore confinement effect and structure adjustment.However,it is very easy for metal agglomerate,and its microporous feature hamper mass transfer of reaction.Based on these problems.a series of non-precious metal ORR electrocatalysts with high activity and excellent stability were prepared by the mixed linker strategy.The main research contents are as follows:(1)In order to regulate the density of active site and stability of the ORR catalysts,a series of non-precious metal-based Fe-N/Ccpur ORR electrocatalysts were synthesized via the mixed linkers strategy.After linkers adjustment,the obtained Fe-N/CCpur-25 catalyst creat macroporous structure,which is conducive to mass transfer.Then ICP characterization shows that the double-linkers catalyst Fe-N/Ccpur-25 can anchor higher content of metal Fe,compared with single-linker Fe-N/CCpur-0,indicating that Fe-N/CCpur-25 catalyst can undertake more active sites.At the same time,Fe-N/CCpur-25 catalyst shows great performance which its half-wave potential is close to 0.8 V during the ORR electrochemical test,which is comparable to commercial Pt/C performance.However,the current still retains 88%after the 50000 s cycle stability test.In addition,in the H2/O2 proton exchange membrane fuel cell test assembled with Fe-N/Ccpur-25 catalyst,the peak power density and open circuit voltage were 560 mW cm-2 and 0.897 V,respectively.Therfore,the regulation of pore structure of the catalyst based on the mixed linkers strategy can not only effectively expose active sites of the catalyst,but also provide an idea for the preparation of other types of catalysts via this method.(2)In order to further explore the role of the regulation of the second linker structure in improving the ORR activity of Fe-N-C catalysts,2,6-diaminopyridine with pyridine N structure was preferred as the second linker to prepare a series of non-precious metal-based Fe-N/CDpyr ORR electrocatalysts in this chapter.After the adjustments of linkers,the Fe-N/CDpyr-25 catalyst shows the best performance.Its half-wave potential is close to 0.81 V,which is similar to the commercial Pt/C.And its stability is well.It also shows excellent methanol resistance performance.Therfore,the choice of the linkers provide some reference for the preparation of catalysts with different applications.