Fabrication Of The Palladium-based Composite Catalysts And Study Of Their Electrocatalytic Properties For Small Organic Molecules

Due to the continuous consumption of fossil fuels and the increasing energy demand,developing clean and efficient energy sources is an urgent problem in the 21st century,the emergency of fuel cells bring hope to mitigate the problem.Fuel cells are able to convert the chemical energy of small-molecule fuels directly into electricity,it considered as a promising green technology for the portable device.Fuel cells have aroused widespread attention in domestic academe because of its many adventages,such as abundant sources,high power densit,clean environment-friendly and high energy conversion.Nowadays,platinum is still the preferred material of anode catalyst in fuel cells,but the high price and poor anti-poisonous of Pt metal impede the commercialization of fuel cells.To improve the catalytic efficiency and decrease the cost of the catalyst have always been the research hotspots of fuel cell.Recently,it has been proved that palladium(Pd)has a similar catalytic activity to platinum(Pt),which has relatively lower cost and higher resistance to CO poisoning.The work of this paper have mainly focused on the following aspects:First,by controlling the morphology of the Pd metal to improve the activity of catalyst,the Pd nano-leaves/RGO catalysts have been successfully fabricated by the cyclic voltammetry;the second,using the synergistic effects of the Pd and Au to improve the catalytic activity,electrical conductivity and anti-poisonous of the catalyst;the third,we have designed and fabricated the flowerlike Pd/Ni(OH)2 catalyst for ethanol electrooxidation.The introduction of Ni(OH)2 as a cocatalyst can greatly facilitate the dissociative adsorption of water molecules and subsequently assists in the oxidative removal of carbonaceous poison.This work takes the above three points into consideration,different methods have been employed to prepare a series of palladium based catalysts.The electrocatalytic performance of the catalysts toward ethanol and formic acid have been investigated in detail.The main research contens are summarized as below:(1)By controlling the morphology of the Pd metal to improve the activity of catalyst,the Pd nano-leaves/RGO catalysts have been successfully fabricated by the cyclic voltammetry.The unique nano-leaves structure shows a larger electrochemical active area(ECSA),which can provide more active sites.As shown by the result of the cyclic voltammetry and chronoamperometry,compared with Pd nano-leaves/GCE and commercial Pd/C/GCE,the Pd nano-leaves/RGO/GCE exhibits better catalytic activity and stability towards formic acid electrooxidation.(2)We have fabricated the Pd/Ni(OH)2 catalyst by chemical reduction method.The flowerlike Pd nanoparticles exhibited the three-dimensional interstitial structure,which may greatly increase the electrolyte accessible surface area of flowerlike Pd nanoparticles.And that every flowerlike Pd nanoparticles are evenly dispersed on the surface of the Ni(OH)2.The introduction of Ni(OH)2 as a cocatalyst can greatly facilitate the dissociative adsorption of water molecules and subsequently assists in the oxidative removal of carbonaceous poison.Compared with the commercial Pd/C catalyst,the Pd/Ni(OH)2 exhibits a significantly enhanced electrocatalytic activity,cycling stability and CO poisoning tolerance for ethanol electrooxidation.(3)First,the Pd nanocubes have been synthesized.Afterwards,we have used Pd nanocubes as the structure-directing cores for the fabrication of Au-decorated Pd bimetallic heterostructures catalysts.The heterogeneous structure and their composition have been verified by TEM,EDS,XPS and XRD techniques.The electrocatalytic performance of the Au-decorated Pd has been demonstrated by the electrochemical method.We found that this decorated structure can enhance the catalytic activity,electrical conductivity,stability and poisoning tolerance of monometallic Pd.