Bimetallic And Support Composite Catalysts And Their Electrocatalytic Oxidation Of Methanol

With the consumption of fossil fuels,the shortage of energy and the increase of environmental pollution,it is of great significance to find safe,renewable,and alter-native green energy sources.Among all kinds of innovative devices of portable pow-er supply,direct alcohol fuel cell as an alternative energy source,has attracted exten-sive research interest because of its environmental friendliness,convenient transpor-tation,alcohol storage,high energy efficiency and simple operation.Great research efforts are devoted to the manufacture of efficient catalysts for direct methanol fuel cell(DMFC).However,it is still hindered by the high cost of platinum,the instability of catalyst in the reaction process and the slow methanol oxidation reaction.There-fore,designing and manufacturing the economical and feasible anode catalysts for methanol oxidation reaction is one of the challenges faced by direct methanol fuel cells in recent decades.In this thesis,different bimetals supported on the carrier were synthesized by optimizing preparation method and process,morphology and compo-sition of the catalysts.The structure of the catalyst was characterized by SEM,TEM and XRD,and its electrocatalytic performance for methanol under alkaline conditions was studied.The specific contents of this thesis are as follows:(1)A Pd@Ag/ZnO composite electrochemical catalyst was successfully pre-pared,which may replace the expensive Pt catalyst for direct methanol fuel cell.The specific activity of Pd@Ag/ZnO catalyst is 1.8,2.8 and 4.6 times higher than that of Pd/ZnO catalyst,20%Pd/C catalyst and Pd black catalyst,respectively.The im-provement of catalytic mechanism should be due to the synergistic effect between Pd@Ag and ZnO.The results of density functional theory(DFT)show that Ag doped with Pd weakens the adsorption of carbon monoxide and significantly improves the ability of resisting CO poisoning.(2)We use TiO₂ as the carrier,and under the condition of heating in water bath,we add the precursors of Pd and Ru,and use them as reducing agents in ascorbic acid and then synthesize Pd Ru/TiO₂ catalyst.XRD and XPS characterizations showed that the catalyst was successfully synthesized,and there was a synergistic effect among Pd,Ru,TiO₂.The improvement of catalytic performance came from the accelerated electron transfer at the interface between metal and support and the change of their electronic structure.Among them,mesoporous TiO₂ shows large surface area,uni-form pore size,accessible open framework and commercial availability,and is a noteworthy promoter for noble metal-based catalysts.Compared with other catalysts such as Pd/TiO₂ and Ru/TiO₂,Pd Ru/TiO₂ catalyst has the largest active surface area and the best electrocatalytic performance.(3)We synthesized TiO₂-RGO complex as carrier to synthesize Pd Co/TiO₂-RGO catalyst by water bath method.SEM and TEM characterizations showed that Pd Co alloy was uniformly distributed on TiO₂-RGO carrier.The interac-tion between Pd Co improved the catalytic activity of the catalyst,and the open struc-ture of the carrier enabled more loading of Pd Co alloy on the surface,exposing more active sites.The dopant of Co metal made catalyst easierly adsorb-OH,accelerating the release of active sites via removal of CO by oxidation.Pd Co/TiO₂-RGO catalyst shows excellent catalytic activity,stability,and resistance to CO toxicity.