Preparation Of Iron-Based Electrocatalyst And Its Application In Oxygen Reduction/Precipitation Reaction

Oxygen reduction reaction（ORR）is the key reaction of fuel cell.Due to its sluggish of reaction kinetics,platinum as the noble metal catalysts is needed to promote ORR.However,noble metal catalysts have some disadvantages,such as high economic cost,easy poisoning and poor stability,which seriously hinder the development of electrochemical devices.As one of the important reactants of fuel cell,hydrogen（H₂）can be prepared by electrolysis of water.However,the oxygen evolution reaction（OER）in the process of electrolyzing water has high overpotential and slow reaction rate,it is necessary to use catalysts to reduce the energy barrier of OER.At present,materials based noble metals Iridium（Ir）and Ruthenium（Ru）are more effective OER catalysts,but the increase of cost restricts the promotion of electrolytic water to H₂.Therefore,the development of non-noble metal-based catalysts is very important.In recent years,iron-based catalysts have attracted much attention because of their low cost,unique electronic structure and high catalytic activity.In order to design low-cost and efficient ORR and OER catalysts,a series of iron-based catalysts were prepared by high-temperature calcination and hydrothermal synthesis.The specific work is as follows:（1）Ferrous acetate and cobalt acetate were mixed with phenanthroline to form a complex,which was adsorbed on zeolite structure（ZIF-8）throughπ-πaction.Then it was carbonized to form the catalyst（Fe Co-NC）.By adjusting the ratio between metal and phenanthroline and the ratio between metals,the coordination environment of metals is further optimized,the electronic structure of local carbon atoms is improved,and the synergy between bimetals improves the catalytic performance of ORR catalyst.The half wave potential(E_1/2)of the Fe Co-NC is 20 m V higher than commercial Platinum Carbon Catalyst（Pt/C）.After 5000 cycles of cyclic voltammetry（CV）,the linear voltammetry（LSV）curve only shifts a little.（2）After the leaf shaped metal organic framework（ZIF-L）formed a stable two-dimensional structure,Fe SO₄ was added dropwise,then different sulfur（S）doping methods were changed,and finally the catalyst（Fe-S-NC）was prepared by carbonization.The good accessibility of two-dimensional structure and heteroatomic iron（Fe）,S can improve the ORR performance of the catalyst in terms of morphology and local electronic structure.The E_1/2 of Fe-S-NC is 30 m V higher than that of Pt/C,and it still maintains good activity after 80000 s.（3）Metal（Fe,cobalt（Co）,manganese（Mn））oxide nanosheets were grown on nickel mesh by hydrothermal synthesis,and directly used as anode electrode for OER.Fe Co Mn based catalysts with different metal ratios are obtained by adjusting the ratio between precursor metal salts.When the ratio of metal Fe,Co and Mn is 1:2:5,the catalyst electrode has large electrochemical specific surface area and good conductivity,the overpotential with current density of 10 m A cm^-2 is only 200 mV,and the limiting current density is 360 mA cm^-2.