Study On The Synthesis Of Nanoporous Pd-based Composite Materials And Catalytic Properties For Alcohols Electro-oxidation

As a new type of battery equipment,direct alcohol fuel cell?DAFC?has the advantages of low temperature operation,high energy conversion efficiency and low emissions,and is widely used in multi-purpose portable mobile devices and a variety of small electronic devices.At present,Pt-based catalyst is the best anode catalyst,but its high cost and low long-term stability greatly limit the wide application in this field.Therefore,the preparation of non-Pt catalysts has become a research hotspot in the field of DAFC.The chemical properties of Pd elements are similar to Pt.And Pd elements have more abundant reserves in nature,and shows better poison resistance compared to Pt.Therefore,Pd-based catalyst is regarded as one kind of promising anode catalysts towards alcohol electro-oxidation.The transition metal oxides CuO,TiO₂ and NiO can promote the formation of oxygen groups on the surface of Pd,and further reduce the potential of oxidation of intermediates and improve the ability of catalyst to resist intermediate products such as CO.By introducing the other alloying elements Ni and Sn,the electronic state of Pd can be modified due to the electron effect between Ni/Sn and Pd,which promotes the adsorption of oxygen-containing groups at lower potential,thus exhibiting excellent electrocatalytic activity and antitoxic properties.It is expected to get better performance of the fuel cell anode catalysts by preparing Pd-based composite materials.In this paper,np-CuO/TiO₂/Pd-NiO composite catalyst was obtained by chemical dealloying method in HCl solution.The microstructure and composition of the samples are characterized by SEM,XRD,XPS and TEM.And the electrochemical methods?CV,CA and EIS?are applied to evaluate the electrochemical performance of the samples.According to the results,the sample prepared in 0.75 M HCl solution at the temperature of 363 K for 5 h had the best electrochemical activity for methanol and ethanol electro-oxidation,and the oxidation current densities are 8.32 mA cm^-2and 2.61 mA cm^-22 for methanol and ethanol,respectively.In addition,np-Pd-Sn and np-Pd₅/Sn₁₀-CuO composite catalysts were obtained by dealloying reaction in alkaline condition.Due to the electronic effect and bifunctional mechanism between Sn and Pd,np-Pd₅-Sn₁₀0 catalyst had the highest oxidation current density(8.70 mA cm^-2).When the Cu element was introduced into the precursor alloy,the long-term stability of the electrocatalyst was greatly improved due to the bifunctional effect provided by CuO.After the CA test of 3000 s,the current density of np-Pd₅/Sn₁₀-CuO composite catalyst maintains 0.63 mA cm^-2.