Synthesis Of Supported Palladium Nickel Copper Nanocomposites And Their Catalytic Properties For Hydrolytic Dehydrogenation Of Ammonia Borane

Hydrogen gas as one of green efficient energies has attracted the attention of the world,due to the superior properties of its safety and environmental friendship.However,the safe storage and transportation of hydrogen is the key points in the development of hydrogen technology.Owing to low density,good stability and high content of hydrogen storage,ammonia borane?NH₃BH₃,AB?is denoted as be one of the ideal materials for hydrogen storage materials.But in absence of suitable catalysts,the very slow rate of hydrogen generation from NH₃BH₃ has severely impeded the application of NH₃BH₃ in the actual hydrogen production.After the whole review of the recent research progress focused on the catalytic dehydrogenation from NH₃BH₃,herein,the supported palladium nickel and copper nanocomposite catalysts has been contronally prepared,and inverstigated on the catalytic properties of NH₃BH₃ dehydrogenation in detail.My research works is as follows:?1?The catalyst of palladium nanoparticles supported on layered double hydroxide?LDH?were synthesized and their catalytic properties were researched.In this chapter,the ZIF-67 nanocubes used as a template to form a hollow NiCo LDH nanoboxes by etching.Under the condition of no additional reductant,the LDH of two phase states loaded the highly dispersed Pd nanoparticles?NPs?,named Pd NPs/?-LDH and Pd NPs/?-LDH,were prepared by hydrothermal method in situ synthesis of LDH with palladium.And the nanocatalyst fully characterized by SEM-EDS,ICP-OES,XRD,TEM,HR-TEM and XPS techniques.In the study of catalytic hydrolysis of NH₃BH₃,the Pd NPs/?-LDH exhibited the enhanced performance in comparison with Pd NPs/?-LDH.At 298 K,the TOF can reach 49.5 mol_H2·mol_Pd^-1·min^-11 and the activation energy is 20.56 kJ·mol^-1,which is superior to many palladium based catalysts reported for this reaction.This may be due to the porous structure,large specific surface area and light weight of LDH.In addition,the synergistic action between rich OH^-of?-phase LDH layer and active center Pd NPs can promote the fracture of B-H in NH₃BH₃.?2?The catalysts of CeO₂ doped CuNi alloy nanoparticles supported on graphene oxide were synthesized,and its performance of catalytic dehydrogenation of NH₃BH₃ and catalytic activity for the reduction of p-nitrophenol were studied.CeO₂-doped CuNi nanoparticles were immobilized on graphene by co-reduction in nitrogen atmosphere,characterized by SEM-EDS,ICP-OES,XRD,TEM and XPS techniques.A series of the as-synthesized CuNi-CeO₂/rGO NCs with various metal contents had been employed as heterogeneous catalysts for the hydrolytic dehydrogenation of NH₃BH₃ under mild conditions,it is found that the catalytic effect of the optimal catalyst of Cu_0.8Ni_0.2-CeO₂/rGO with CeO₂ content of 13.9 mol%exhibited the best catalytic effect.The exceedingly high TOF value is 34.4 mol_H2·mol^-1_cat.·min^-11 at 298 K.The apparent activation energy was calculated to be 19.1 kJ·mol^-1,even lower than most of noble-metal-based catalysts for AB dehydrogenation.Moreover,the obtained in situ hydrogen from AB hydrolysis can be further applied to reduce 4-nitrophenol with a high TOF value of 8.1 min^-1at room temperature.?3?The catalysts of CeO₂ doped PdNi alloy nanoparticles supported on graphene oxide?PdNi-CeO₂/rGO?were synthesized,and its the catalytic properties of the catalyst were studied.CeO₂-doped PdNi alloy NPs supported on the rGOwere prepared by a simple co-reduction approach in aqueous solution at room temperature,and characterized by SEM-EDS,ICP-OES,XRD,TEM,HR-TEM and XPS techniques.All the results revealed that PdNi-CeO₂ nanoparticles were uniformly dispersed on rGO.The as-synthesized PdNi-CeO₂/rGO with different metal contents had been employed as heterogeneous catalysts for the hydrolytic dehydrogenation of NH₃BH₃,it is found that the catalytic effect of the optimized catalyst of Pd_0.8Ni_0.2-CeO₂/rGO with CeO₂ content of 13.9mol%exhibited an excellent catalytic activity.The exceedingly high TOF value is 30.5mol_H2·mol^-1_cat.·min^-11 at 298 K,and the apparent activation energy was calculated to be37.78 kJ·mol^-1.The high activity of Pd_0.8Ni_0.2-CeO₂/rGO would be attributed to the small size of PdNi-CeO₂ NPs,metal-metal synergy,and the metal-support interaction.Additionally,the hydrogen-released rate was found to be first-order with respect to the catalyst concentration.