Synthesis And Catalytic Performance Of Pd-based/Ru-based Porous Nanocomposites

Currently,direct alcohol fuel cells attracted significant attention because of its low orzeroemission,notoxicity,highlyefficientfuelutilizationand environmentally-friendly operations.Some poisonous intermediates will be generated and strongly adsorbed on catalyst surface in the process of electro-oxidation,blocking the surface active sites from further catalysis.Therefore,excellent electrocatalyst design strategies must be applied to strengthen the activity and anti-poisoning issues associated with both the catalyst metal particles and carbon supports to achieve practical adoption targets.Since the electrocatalysis is a surface reaction,the eletrocatalytical performance is largely determined by the shape and composition of catalysts.Therefore,optimizing the structure of Pd,such as alloying surface decorating and chosing supports etc.,becomes the key point in the explorion of highly active and stable catalysts.Ammonia borane?NH₃BH₃,denoted as AB?appears to be an appropriate hydrogen storage material because of its high hydrogen content?19.6wt.%?,excellent stability under ambient conditions and environmental benignancy.So far,noble metal?Pd,Ru?,transition metal?Co,Ni?NPs and non-metal phosphorus are tested for hydrolytic dehydrogenation of AB.The experimental results show that noble metal NPs have been identified to be effective for catalytic hydrolysis of AB,more non-noble metal component in the catalyst not only improves the catalytic activity,but also reduces the cost which is the key to building a sustainable development of industry in the future.TiO₂ hollow spheres?TiO₂HS?and Metal-organic frameworks?UIO66?have extensive application prospect in the field of catalyst carrier,due to their high specific surface area,large length to diameter ratio,high performance of chemical inertness and good conductivity.In our works,the following results were mainly included:?1?The TiO₂ hollow spheres?TiO₂HS?were successfully prepared by a hydrothermal method and added to Vulcan XC-72 carbon black as the support materials for Pd nanoparticles.A facile approach to promote ethylene glycol?EG?electrooxidation in alkaline medium was carried out by the PdBi/TiO₂HS-C catalyst.The results show that Pd and Bi nanoparticles are uniformly dispersed on the surface of carbon-doped TiO₂ hollow spheres,the appropriate amount of Bi modification into Pd/TiO₂HS-C catalyst can enhance remarkably the electrocatalytic activity for EG oxidation,in which the PdBi/TiO₂HS-C?Pd:Bi=1:0.1?catalyst exhibits excellent stability.The high electrochemical performance is attributed to the unique structure and high surface area of the TiO₂HS,metal nanoparticles uniform distribution,the electronic effect between Pd and Bi as well as the bifunctional effect between metal nanoparticles and the support TiO₂HS-C.The results obtained are significant for the development of new Pd-based TiO₂HS-C electrocatalysts for alcohol fuel cells.?2?Bimetallic PdNi nanoparticles with different molar ratios supported on TiO₂HS have been successfully synthesized by a simple liquid impregnation-reduction method.And a series of techniques were employed to characterize the above catalysts,and their catalytic activities were tested in the hydrogen generation from aqueous solution of ammonia borane at room temperature.The results show that the as-synthesized Pd₁Ni_0.6/TiO₂HS catalyst exhibits the highest catalytic activity,with a total turn over frequency?TOF?value of 105.36 mol H₂ min^-1?mol Pd?^-1,and the activation energy?Ea?is determined to be 24.86 kJ/mol.The excellent catalytic activity has been successfully achieved thanks to the strong bimetallic synergistic effects from PdNi nanoparticals of the composites,uniform distribution of nanoparticles as well as bifunctional effects between PdNi nanoparticles and the host of TiO₂HS.In particular,this catalyst shows satisfying durable stability after five cycles.?3?A new noble metal/non-noble metal RuP@UIO66 catalyst was successfully prepared by the sodium hypophosphite reduction method.XRD,TEM,ICP-AES and XPS techniques have been employed to analyze the catalyst's crystal structure,morphology,metal content and valence state.Their catalytic activities were tested in the hydrogen generation from aqueous solution of ammonia borane at room temperature.It can be found that the RuP@UIO66 catalyst displays higher catalytic activity than that of monometallic Ru@UIO66 catalyst,in which the presence of non-metal phosphorus helps to reduce the size of Ru nanoparticles by acting as a surface protecting agent,enhances the electronic effect between Ru and P.The TOF value of RuP@UIO66 catalyst is 396.04 mol H₂ min^-1?mol Ru?^-1,and the Ea is determined to be 33.15 kJ/mol.In addition,54.55%of the initial activity is retained after five cycles.