Study On The Preparation And Performance Of Non Precious Metal Catalys For Oxygen Reduction Reaction

Fuel cell is the most effective device to utilize clean energy such as hydrogen,and it have attracted many attentions due to their high energy conversion efficiency and little pollution.Both the reactions of hydrogen oxidation and oxygen reduction in fuel cell are very slow,it have to use platinum element to catalyst the reaction.Nevertheless,the oxygen reduction is more slower than hydrogen oxidization,which lead to the more usage of platinum element.However,the rare content and high price of platinum element cannot bear the large-scale application of fuel cell.Transition metal oxides and carbides materials have vast investigation because of their considerable activity towards oxygen reduction reaction.Among them,the manganese and iron element have the advantage of polyvalences and starting material cheap and easy to get,which can be one of the best candidate to replace platinum element.But these materials have the disadvantage of poor electrical conductivity and less activity sites,which lead to the poor oxygen reduction reaction compared with platinum element.Thus,the catalyst activity improvement of these materials are very essential.In this paper,by adjust the size and morphology,doped with rare earth in the metal oxide,improving the activity sites in the metal carbide,we have controlled synthesis spinel MnCo2O4,La-doped CaMnO3,Fe3C/C nanofiber,the electrochemical reduction oxygen has been investigate.First,a solvothermal method is used to synthesis carbonate precursor,a porous spinel MnCo2O4 is obtained followed by calcination in air.By adding the different molar of ammonium acetate during the synthesis procedure,the porous spinel MnCo2O4 size and morphology have been changed.The optimized MCO-10 catalyst exhibit the most positive onset potential at-0.15 V,the max limited diffusion density of 5.0 mA cm-2 at-0.7 V,which have a comparable value of Pt/C at 5.2 mA cm-2.Then,calcium alginate is used as precursor,a facile ion exchange method is used to synthesis perovskite structure CaMnO3 and a series La-doped CaMnO3.The La-doped CaMnO3 not only decrease the crystal particle size but also increase the specific surface area.The optimized 10% LCMO catalyst exhibit the most positive half wave potential at-0.15 V,the max limited diffusion density of 5.37 mA cm-2 at-0.7 V.Last,Prussian blue and PAN are used as precursor,an electrospinning technical followed by a pyrolysis is used to synthesis nanofiber structure Fe3C/C.The nanofiber structure can provide even higher specific surface area and porosity ratio,which are very essential to provide more activity sites and enhance mass transfer.The optimized Fe3C/C-900 catalyst exhibit the most positive half wave potential at-0.224 V,the max limited diffusion density of 5.01 mA cm-2 at-0.9 V.