Study On Application Of Metal Oxide In Direct Alcohol Fuel Cells

Direct alcohol fuel cell(DAFC)is a kind of electrical generation device.It converts directly chemical energy,which is saved up in fuels and oxidant,to electric energy.And it is the fourth electrical generation technology after water power,thermal power and nuclear power,which will be the preferrred,undefiled,high efficiency electricity power in the 21 centure.With the development of DAFC investigation,this green energy technology becomes mature,which is of great importance for sovling scarcity of energy sources and environmental pollution.However,the most problems are the low electrochemical activity of anodic catalysts and high "methanol crossover" through the proton exchange membrane(PEM)which will depress the activity of cathode.Especially,noble metal Pt with high price is still the primary catalysts for DAFC.Therefore,it is necessary to prepare catalysts with low loading and high activity,which is also an effective way to reduce the cost of fuel cell.In this paper, Pt-CeO_x/graphite,Pt-MoO_x/CNT/graphite and Pt/MgO-CeO₂-CNT/graphite electrodes were prepared and their electrochemical properties were investigated in detail.The main works involved in this thesis are presented as follows;1.CeO_x nanoparticles used in this study was prepared by agglomeration at high temperature,then complexed with Pt to form the new highly dispersed anode catalyst. The electrocatalytic properties of Pt- CeO_x catalyst supported on graphite electrode for methanol oxidation have been investigated in 1.0 M CH₃OH+0.1 M H₂SO₄ by cycle voltammetry(CV).Pt- CeO_x/graphite electrode were also characterized by scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).On the other hand,the effect of different ratio of Pt;CeO_x on the performance of the catalyst was investigated.The results indicate that the Pt-CeO_x/graphite electrode shows higher electrocatalytic activity and good long-term cycle stability for methanol oxidation.2.MoO_x,a non-noble secondary catalyst instead of noble metal Ru,was dispersed on carbon nanotubes(CNT)and then the primary catalyst Pt was electrodeposited on MoO_x/CNT/graphite electrode by potential-step method.CNT used in this paper was grown directly on graphite disk by chemical vapor deposition.The Pt-MoO_x/CNT/graphite electrode was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy.The electrocatalytic property and the long-term cyclic stability of Pt-MoO_x/CNT/graphite electrode for ethanol oxidation have been investigated in 1.0 mol/L CH₃CH₂OH+0.1 mol/L H₂SO₄ by cyclic voltammetry.On the other hand,the effect of the loading mass of MoO_x on specific activity of Pt-MoO_x/CNT/graphite electrode and the activation energy of ethanol oxidation were investigated.The results indicate that the specific activity of the Pt-MoO_x/CNT/graphite electrode is little lower than that of Pt-Ru/CNT/graphite electrode,but much higher than that of Pt/CNT/graphite electrode.Also,the Pt-MoO_x/CNT/graphite electrode shows good long-term cycle stability.3.Pt/MgO-CeO₂-CNT hybrid electrocatalyst for ethanol electrooxidation were simply prepared.The micrographs and element compositions of Pt/MgO-CeO₂-CNT catalyst were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy,respectively.The electrocatalytic properties of Pt/MgO-CeO₂-CNT catalyst for ethanol oxidation have been investigated by cyclic voltammetry in the basic solution.The effect of the content of MgO and CeO₂ of Pt/MgO-CeO₂-CNT catalyst on the ethanol electrocatalytic activity was also investigated.Under the same Pt loading mass and experimental conditions for ethanol oxidation,Pt/MgO-CeO₂-CNT catalyst shows higher electrocatalytic activity than Pt/CNT catalysts.Additionally,Pt/MgO-CeO₂-CNT catalysts possess a good anti-poisoning ability.