A Study On The Construction Of Pd-based Electrocatalyst And Their Catalytic Performance In Ethanol Oxidation Reaction

The direct ethanol fuel cells are expected to be a candidate to solve the fossil energy crisis and alleviate the trend of environmental degradation.As the core component,the anode catalyst has always been the research and development objectives of the majority of researchers.In addition,the process of ethanol oxidation reaction is very complex,during which a large number of intermediate species are produced,which will poison the active sites of the catalyst and reduce the catalytic activity.Based on this background,single Pd catalysts were synthesized and their adsorption and catalytic behavior in 1 mol·dm^-3 KOH and 1 mol·dm^-3 KOH+1mol·dm^-3 EtOH solution were studied.Then,binary Pd-Sn/C,Pd-Co/C and ternary Pd-Sn-Cu catalysts were prepared and applied to study the ethanol oxidation reaction performance.Finally,through the joint analysis of the material microstructure changes and the macroscopic electrocatalytic test results.Overall,this work aims to develop efficient and stable catalysts for direct ethanol fuel cells.The specific research contents of this works are as follows:（1）The single Pd catalyst with a clean surface was prepared by in-situ electrochemical deposition on the glassy carbon electrode at room temperature.The adsorption and catalytic behavior were studied by cyclic voltammetry in 1 mol·dm^-3KOH and 1 mol·dm^-3 KOH+1 mol·dm^-3 EtOH solution and the possible reactions on the surface of the catalyst at different potentials were analyzed.However,the single Pt catalyst was also prepared by the same method,and the research focused on the adsorption kinetics of OH^-and the oxidation characteristics of CO_ads for the single Pd and Pt catalysts.The test results showed that the adsorption of OH^-on Pd and Pt surfaces was controlled by surface diffusion kinetics.When the surface adsorbed CO_ads,Pd and Pt have a similar initial oxidation potential,which means that the anti-CO_ads poisoning capability of Pd is equivalent to that of Pt.（2）Carbon supported binary Pd-Snand Pd-Co composite catalysts with different ratios were prepared by low-temperature impregnation reduction method.XRD test and result analysis showed that the doping of different atomic radius elements would produce a compression/expansion effect on the lattice of Pd.Combined with the peak current density of positive and negative scanning in the ethanol oxidation reaction,macro metal doping and microstructure changes caused by doping,factors that may affect the ethanol oxidation reaction were analyzed.（3）The ternary Pd-Sn-Cu composite catalysts were synthesized with the aid of surfactants and applied to the ethanol oxidation reaction.The TEM and XPS results showed that there was a certain part of element separation on the surface of the as-prepared Pd₆₁Sn₃₄Cu₅ catalyst,that was,the separation of Snand Pd-Cu.Most of the Snon the surface of the material was in the form of SnO _x species,and part of the Snor SnO_x species was exposed to the outside of the material in the form of a non-alloy phase.Besides,the Pd61Sn34Cu5 catalyst provided 1.26 A·mg_Pd^-1of mass activity for the ethanol oxidation reaction,which was about 2.21 times greater than that of the commercial Pd/C catalyst.The Pd₆₁Sn₃₄Cu₅ catalyst also displayed remarkable electrocatalytic stability with a weak electrocatalytic activity loss in the current-time test and 500 cycling stability tests.