Preparation And Electrochemical Performance Study Of Oxygen Reduction Reaction Catalyst For Air Cathode

As highly efficient and clean energy electrochemical power generation device, the metal-air and fuel cells in alkaline play a significant role in the area of new energy, are attracted more and more attention. One of the most important factors determining the performance of fuel cells is the oxygen reduction reaction?ORR? of air cathode, so the research of highly active ORR catalyst materials has a very important significance. Graphene, a one-atom thick and two-dimensional honeycomb lattice of carbon nanomaterials, due to the good electrical conductivity, large surface area and high electro-catalytic activity, have usually been regarded as an ideal part of a composite material.In this paper, the Mn Ox/graphene and Ag-MnO₂/graphene composites are synthesized via different materials and methods, and characterize the properties for the composites by a variety of testing methods.Petal-like MnOx/graphene composite is synthesized through a reflux-calcination method. The different amounts of MnCl2·H2O, urea and the calcination temperature as well as refluxed time have a major impact in the product morphology, structure and the distribution on graphene sheets. The catalyst owns the best ORR activity with the MnOx mass fraction of 48%. Raman, XRD and TEM test results show that the 3 nm nanoparticles of manganese oxide distribution evenly on graphene sheets. The cyclic voltammograms?CV? demonstrate that 48% MnOx/graphene catalyst exhibits positive oxygen reduction potential of-0.29 V vs.Hg/HgO in alkaline solution. From the linear sweep voltammograms?LSV? show that the catalyst has a small resistance and a higher limiting current density, during the ORR process, it is calculated to possess the two –electron?2e? pathway.Ag-MnO₂/graphene composite is prepared by immerse-calcination method. The composite composed of Ag? 6 nm? and MnO₂? 4 nm? nanoparticles are homogeneously distribution on the graphene sheets. The CV, LSV and Tafel curves results show that the oxygen reduction peak potential of Ag-MnO₂/graphene cathode is-0.15 V, which is more positive than 20% Pt/C?-0.19 V? vs.Hg/HgO. The catalyst shows lower over-potential and higher ORR reduction current. According to the KouteckyLevich curves and the related formula calculated results: the catalytic process of AgMnO₂/graphene via four-electron?4e? pathway.