Preparation Of Transition Metal Nanoparticles And Their Catalytic Properties For Hydrolytic Dehydrogenation Of Ammonia Borane

As a promising clean energy source,hydrogen(H2)has drawn much attention due to its merits for replacing non-renewable energy.However,one of the barriers to realize the H2 energy society is the efficient and safe storage of H2 because of its gaseous under mild conditions.Ammonia borane exhibits the advantages of non-toxic,high stability in solutions,high hydrogen density(19.6 wt %),and low molar molecular weight,making it a highly promising candidate for hydrogen storage.The key to large-scale application of AB as a hydrogen storage meterials is to develop efficient,economical and pollution-free catalyst.The main results in this paper are divided into three parts as following:Firstly,Pt-based nanomaterials have been employed to catalyze the hydrolysis of AB because of its superior catalytic properties,high selectivity and long-life.At present,the particle size of Pt-based alloy nanoparticles is more than 5 nm,which hinders the further improvement of its catalytic activity.In order to reduce the size of Pt-based alloy nanoparticles and improve their catalytic activity,we chose long chain-NH2 modifed GO as the supported meterials and prepared NH2-N-r GO supported ultrafine Pt-Pd alloy nanoparticles by a simple in-situ reduction method.Du to the electron effect between Pd and Pt and the electronic structure effect between NH2-N-r GO support and Pt-Pd NPs,the catalytic activity of the Pt0.5Pd0.5/NH2-N-r GO complex for the hydrolytic dehydrogenation of AB was significantly improved under room temperature with an initial turnover frequency of 699.6 mol(hydrogen)·mol(catalyst)-1·min-1 and an apparent activation energy of 37 k J·mol-1.Secondly,in order to reduce the use of precious metals,we introduced transition metal Cu into Pt NPs to form alloy structure.The Pt-Cu alloy nanoparticles were prepared by high temperature liquid phase method with OAm as solvent,surfactant and reduction.Pt-Cu NPs were assembled on Ketjen carbon support by sonicating the mixture of Pt Cu NPs-hexane and Ketjen carbon-ethanol dispersions.The results show the Cu50Pt50/CB complex exhibit excellent catalytic activity with an initial turnover frequency of 98 mol(hydrogen)·mol(catalyst)-1·min-1 and an apparent activation energy of 36.5 k J·mol-1.As a new semiconductor carrier material,graphite-phase carbon nitride(g-C3N4)has attracted wide-spread attention owing to its potential applications in solar energy conversion and photocatalysis in recent years.Nanoparticles catalyst based on non-noble metal,such as Cu,Co,Ni have attracted extensive research interest due to its rich reserves and low cost.Monodisperse Ni NPs were prepared by high temperature liquid phase method with nickel acetylacetone as precursor and g-C3N4 was prepared by thermal polymerization with melamine as reagent.Ni/g-C3N4 complex was prepared by sonicating the mixture of Ni NPs-hexane and g-C3N4-ethanol dispersions and exhibit excellent catalytic activity under light condition with an initial turnover frequency of 18.7 mol(hydrogen)·mol(catalyst)-1·min-1 and an apparent activation energy of 35.7 k J·mol-1.