The Research Of Palladium-based Catalytic Materials For Electro-catalytic Oxidation Of Ethanol And Oxygen Reduction Reaction

In recent years,direct ethanol fuel cell and proton membrane fuel cell has received more and more attention because they have many advantages.The electrocatalytic performance of the catalysts is mainly related to the component,structure and support of the catalysts.We synthesized several kinds of catalysts and studied their electrocatalytic properties for the oxidation of ethanol and ORR,including carbon-supported PdWO/C catalyst,?Pd-Cr/C?catalyst,Pd-based nanoporous Pd-W alloy materials.The X-ray diffraction spectroscopy?XRD?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,and?HRTEM?were used to characterize the catalysts.The cylic voltammetry?CV?,linear sweeping curves?LSV?and chronoamperometric curves?CA?were used to measure the electrocatalytic activity and stability of the catalysts for the oxidation of formic acid.The main results obtained are as follows:1.Carbon loaded oxide-rich Pd-W bimetallic electrocatalysts?PdWO/C?were prepared by chemical reduction methods.The existence of oxides in the electrocatalysts is confirmed by X-ray photoelectron spectrum?XPS?and high resolution transmission electron microscopy.XPS analysis indicates that the oxygen atoms account for about 50% of all the atoms in Pd-W bimetallic nanoparticles.Compared to Pd/C catalyst,the oxide-rich Pd-W bimetallic catalysts exhibited a better catalytic activity for the anode oxidation of ethanol in alkaline media.The improvement of the catalytic activity is attributed to the synergistic effect of W/WO_x.The onset potential of the as prepared oxide-rich Pd_0.8W_0.2/C catalyst?Pd:W=8:2,metal atom ratio?for ethanol oxidation is negative shifted about 90 mV comparing to Pd/C catalyst.The oxide-rich Pd-W/C electrocatalysts provide a new model of Noble-metal/ Promoter system as an extreme case of making the promoter?WO₃?closely adjacent to the noble metal?Pd?by fabricating nanoparticles containing both atom-clusters of oxides and the noble metal atoms.2.A serious of carbon loaded Pd-Cr bimetallic catalysts(Pdx Cr_1-x/C,x=0.6¹,atomic ratio)was prepared by chemical reduction method.Among them,Pd_0.8Cr_0.2/C catalyst exhibits the highest catalytic activity for oxygen reduction reaction.Its activity is better than that of Pd/C and previously reported Pd_0.61Cr_0.39.Pd_0.8Cr_0.2/C also exhibits high stability,which indicates that it is a potential candidate for the cathode of proton exchange membrane fuel cells.3.Nanoporous materials have broad application prospects in the field of electro catalysis,sensors and biology.The reason is that it has special physical and chemical properties because of its special nanostructure.In this chapter,we study the preparation of Pd based nanoporous Pd-W materials by using the dealloying method.Compared to Pd/C,the onset potential of the oxidation of ethanol at nanoporous PdW catalyst exhibits negative shift of about 85 mV.Nanoporous PdW also showed high electrocatalytic stability.