The Design And Synthesis Of Palladium-based Modified Graphene Composites And Their Electrocatalytic Oxidation Of Alcohols

The development and application of direct alcohol fuel cells（DAFC）will solve the problems of natural air pollution and lack of fossil fuels,which have caused widespread concern and research.However,the poor stability and low efficiency of anode electrocatalysts for DAFC make it impossible to use them on a large scale.Therefore,we urgently need to find excellent catalysts.The prepared catalyst support is an effective way to enhance the electrocatalytic function of the catalyst,for example,combining the prominent virtues of different materials to synthesize composites to enhance the advantages of catalyst carriers.What’s more,the surface of precious metal Pd in the catalyst is modified by introducing other non-precious metal nanoparticles to enhance the activity and stability of the catalyst due to the strong synergy effect.For example,alloying is performed by supporting metal nanoparticles such as Ru,Bi,Sn,and Co.Graphene exhibits high electrochemical double-layer capacitance,stability,electrical conductivity and specific surface area.Because the structure of graphene is a thin layer,when the surface structure of graphene is changed,it is easy to cause thin layer graphene to collapse and reduce the specific surface area.Then,the combination of metal organic frameworks（MOFs）or other inorganic metal oxides with graphene can make graphene maintain or even enhance its performance and structural stability,and make the modified graphene composite materials more suitable as carrier for anode electrocatalyst of DAFC.In this study,Pd was used as a noble metal,Ru,Bi,Co and Sn metal nanoparticles were selected as the ligand metals.The new and efficient catalysts Pd RuBi@r GO/MOF-199,Pd Sn Co@r GO/CuBi₂O₄and Pd@r GO/CoSnO₃were successfully prepared by simple hydrothermal impregnation reduction method.Fourier transform infrared（FT-IR）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,thermogravimetric analysis（TGA）,scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）and Brauner-Emmett-Teller（BET）were used to study the physical and chemical properties of the electrocatalysts.The results include:1.Well-dispersed trimetallic Pd-Ru-Bi alloy nanoparticles were successfully embedded in the three-dimensional r GO/MOF-199 by hydrothermal impregnation reduction way.Among the mono-,bi-and tri-metal@r GO/MOF-199 electrocatalysts,the trimetal catalysts Pd RuBi@r GO/MOF-199 shows the best catalytic property and stability towards ethylene glycol oxidation reaction in the alkaline condition.The excellent electrocatalytic oxidation property of Pd RuBi@r GO/MOF-199 is attributed to the unique 3D structure of the support and the strong synergy of Pd,Ru and Bi trimetal nanoalloys,thus supplying sufficient reaction interfaces and active sites.2.The Pd-Sn-Co nanoparticles were immobilized on a graphene/CuBi₂O₄support,and the electrocatalyst Pd Sn Co@r GO/CuBi₂O₄that exhibited a higher catalytic activity for the electrooxidation of ethylene glycol in alkaline media was successfully obtained.The performance was compared with several other comparative catalysts Pd Co@r GO/CuBi₂O₄,Pd Sn@r GO/CuBi₂O₄and Pd@r GO/CuBi₂O₄.It was found that the trimetal catalyst Pd Sn Co@r GO/CuBi₂O₄has the highest current density,the lowest onset potential,the strongest toxicity and durability.Its performance is significantly better than single metal and double metal composite catalysts.The trimetal catalyst exhibits such outstanding electrocatalytic performance due to the unique structure of the graphene introduced in the carrier CuBi₂O₄and the strong synergistic effect between the trimetal,which together promote the electrooxidation of ethylene glycol.3.The composite material obtained by combining CoSnO₃and carbonaceous materials was applied to the electrocatalytic oxidation of organic small molecular alcohols in alkaline media.The effect of composite materials formed by graphene and CoSnO₃is significantly better than that of activated carbon.The catalyst Pd@r GO/CoSnO₃has high catalytic activity for methanol,ethanol and ethylene glycol at the same time.From the catalytic activity shown by the catalysts of different carriers,the excellent catalytic performance of the catalyst Pd@r GO/CoSnO₃is inseparable from the large specific surface area and fast electron transfer ability of the composites support GO/CoSnO₃.The design of preparing the catalysts by a facilehydrothermal impregnation reduction method and a catalyst improved by using a synergistic effect between multiple metals and a modified graphene composite materials as carrier has great significance for the development and application of DAFC anode catalysts.