Synthesis Of Noble Metal Composite Catalysts And Their Electrocatalysis Toward Alcohols

Fuel cell is a kind of eco-friendly energy conversion equipment.Because of the wide range of fuel and high conversion efficiency,fuel cell is an effective choice to solve environmental pollution and energy crisis.As an important part of fuel cell,Electrocatalysts(including catalyst support and noble metal)is the active center of the catalytic reaction,and the performance will directly affect the overall performance and efficiency of the fuel cells.Currently,the most commonly used anode catalyst in fuel cells is platinum,however,the poor anti-poisonous and high cost of Pt seriously impede the development of fuel cell.Therefore,developing suitable catalyst supports,decreasing the amount of noble metals and improving the electrocatalytic activity have always been hot topics in fuel cell study.The electrocatalytic activity of the catalyst can be improved from two aspects,precious metals and catalyst supports.Generally,doping second element in noble metal can change the electronic structure of noble metal and improve the catalyst performance.Another aspect is developing high specific surface area,high stability and low-cost catalyst support,which makes the precious metal disperse evenly,and ultimately improves the unit activity of the noble metal.In this dissertation,a series of electrocatalysts were synthesized through chemical methods,and the catalytic activities of the as-synthesized electrocatalysts toward alcohols oxidation have been explored in detail.The main content in this thesis is listed in the following:(1)Pd/P nanocomposite catalysts with different Pd/P ratios were synthesized by using benzyl alcohol as solution and sodium hypophosphite as phosphorus source.The as-prepared catalysts were characterized by a series of physical and electrochemical methods.Electron microscope results showed that the obtained Pd/P catalyst possess well-defined network structure.The electrochemical results demonstrate that P doped Pd nanocatalyst has the superior electrocatalytic activity toward methanol oxidation in comparison with the monometallic Pd and commercial Pd/C catalyst,and the optimal molar ratio of Pb/P catalysts is 2:1.(2)Dendritic Pd/Ru nanocatalysts have been synthesized by using ascorbic acid as reducing agent and KBr as directing agent.The as-prepared Pd/Ru nanocatalysts have been characterized by XRD,TEM and XPS,the characterization measurements reveal that KBr and Ru play crucial roles in synthesizing the dendritic structure of the catalyst.Electrochemical results show that the Pd/Ru catalyst has the superior catalytic activity and stability toward ethanol electrooxidation reaction.(3)Dendritic Pt/Pb nanocatalysts were facile and rapid synthesized by a one-pot method.The obtained catalysts were analyzed by TEM,XRD,XPS and electrochemical measurements.By controlling the growth parameter,we found that CTAC plays a crucial role in synthesizing the dendritic structure of the catalyst.Electrochemical test results show that the dendritic Pt/Pb catalysts possess the best catalytic performance than the monometallic Pt and commercial Pt/C catalyst for ethanol oxidation reaction,and the optimal molar ratio of Pt/Pb catalysts is 1:1.(4)Pd/Cu₃P/RGO nanocomposite catalyst was synthesized by depositing Pd nanoparticles on Cu₃P modified RGO.The as-formed Pd/Cu₃P/RGO nanocomposite catalyst was extensively analyzed by SEM,XPS,XRD,TEM and electrochemical measurement methods.Electrochemical test results demonstrate that the as-synthesized Pd/Cu₃P/RGO catalyst possesses the best catalytic activity and stability toward alcohols electrooxidation under alkaline condition in comparison with commercial Pd/C and Pd/RGO catalysts.(5)A three-dimensional Au/PANI/RGO catalyst,which uses the tubular PANI as skeleton,was synthesized by chemical reduction of graphene oxide and chloroauric acid with sodium borohydride.The structure and morphology of the Au/PANI/RGO was characterized by SEM,TEM,Raman and XPS.Electrochemical test results reveal that the Au/PANI/RGO nanocatalyst provides superior electrocatalytic activity toward ethanol oxidation as compared to Au/PANI and Au/RGO,demonstrating that PANI/RGO can be used as a catalyst supporting material in direct ethanol fuel cells.