Study On The Enhanced Electrochemical Properties Of Catalysts For Fuel Cells Based On Doping Effect

Fule cells,such as proton exchange membrance fuel cell and direct methanol fuel cells,showed broad application prospects.Oxygen reduction reaction(ORR)played important role in fuel cells.Currently,commercial Pt/C catalyst has been commonly used as the classic oxygen reduction reaction catalyst for the cathode.However,limited resource,high cost and susceptible to corrosion of Pt made it difficult to be applied for commercialization in large–scale.Therefore,the development of unexpensive electrocatalyst with both higher catalytic performance and better durability than Pt noble metal have attracted more and more attention.There are three parts in our work:1.Electrocatalytic study of 1,10–phenanthroline–cobalt(Ⅱ)metal–complex catalyst supported on reduced graphene oxide towards oxygen reduction reactionA new class of oxygen reduction reaction(ORR)catalyst was fabricated by loading 1,10–phenanthroline–cobalt(Ⅱ)metal–complex onto reduced graphene oxide(r GO)surfaces by π-π interaction.The Co(Ⅱ)-N4 was the active center of metal–complex catalyst and catalyzed the ORR via a high efficient four–electron reduction pathway.The introduction of nitro–group substituent in 1,10–phenanthroline highly boosted the catalytic activity of metal–complex in terms of half–wave potential(E1/2)and kinetic current density(JK)due to the downshift of eg–orbital energy level for central Co(Ⅱ)resulted from the electron–withdrawing effect of nitro–group.Considering the configuration of metal–complex on r GO surfaces,a single cobalt center–mediated catalytic mechanism was proposed to elucidate the ORR process.Compared with the commercial Pt/C catalyst,the as–prepared metal–complex catalyst exhibited a superior methanol tolerance and catalytic durability for ORR.Our study provided more information about the relationship between the molecular structure and catalytic activity towards ORR.2.One–step synthesis of MnO/Ni nanoparticles anchored on porous nitrogen–doped carbons from melamine foam and electrocatalytic study towards oxygen reduction reactionThe hybrid catalyst composed of MnO/Ni nanoparticles embedded in branched nitrogen–doped carbons(MnO/Ni@BNCs)were prepared by direct pyrolyzing melamine foams containing Mn(Ⅱ)and Ni(Ⅱ)ions at 800 °C under N2 atmosphere.On the basis of electrochemical tests,it was found that the MnO/Ni@BNCs hybrid catalyst showed a high efficient four–electron catalytic pathway towards oxygen reduction reaction(ORR)and gave a low yield of H2O2(<7.53 %).It also exhibited a superior catalytic stability and methanol tolerance,far exceeding the commercial Pt/C catalyst.The excellent catalytic performance was attributed to the synergetic effect between high catalytic activity of MnO and high electrical conductivity of Ni.Furthermore,the high surface area and porous structure characters of catalyst support,which partially inherited the microstructure of malemine foam,also benefited the electron transfer and reactive species transformation during ORR process.3.Te–template approach to fabricating ternary Te Cu Pt alloy nanowires with enhanced catalytic performance towards oxygen reduction reaction and methanol oxidation reactionFabricating ternary Pt–based alloys has emerged as a promising strategy to further enhance the catalytic performance of Pt catalysts in direct methanol fuel cells(DMFCs)for both the oxygen reduction reaction(ORR)and the methanol oxidation reaction(MOR).Herein,we reported for the first time the synthesis of ternary Te Cu Pt nanowires(NWs)by a Te–template–directed galvanic replacement reaction,in which Te NWs serve as both sacrificial templates and reducing agents.Compared with a binary Te Pt alloy and pure Pt catalysts,the ternary Te Cu Pt alloys exhibit a more positive half–wave potential and a higher specific area/mass activity for ORR,and also display a better CO tolerance ability and long–term stability for MOR.The enhanced catalytic performance for Te Cu Pt NWs is attributed to the electronic and geometric structure effects,originating from the Pt alloying with both Te and Cu components,which could weaken the binding strength between the Pt surface atoms and the intermediate species(e.g.OH*,CO*).Our studies have demonstrated a new alternative ternary Pt–based catalyst for both ORR and MOR,which could find application in DMFC.