The Preparation Of Platinum-based Multi-component Catalysts Doped With Transition Metals And Their Catalytic Performance For Ammonia Evolution Of Borane

Hydrogen energy is the most promising environmental protection energy in the21st century because of its high efficiency and pollution-free,and it is one of the energy that can replace traditional fuel.Most of the hydrogen storage materials face disadvantages such as low hydrogen storage capacity,high equipment requirements,and many by-products,which limit their applications.Ammonia borane contains 19.6wt%hydrogen,and its high hydrogen storage capacity has been attracted the special attention of a large number of researchers.One of the main resistances of ammonia borane used in fuel cells and portable energy supply devices is its slower catalytic kinetics.In this paper,we expect to design catalysts toward catalytic hydrolysis of ammonia borane to release hydrogen gas at a considerable rate.For the moment,the catalytic activity of multicomponent composite catalytic materials is better than that of single component or two components catalytic materials due to the synergistic effect between different components.Here,from the perspective of designing multicomponent catalytic material,we theoretically optimize the chemical composition and structure of the catalyst,and expect to obtain a highly efficient catalytic.In recent years,Pt has been recognized as highly efficient noble metal catalysts,which has been widely used in various fields such as catalyzing hydrolysis of ammonia borane.However,due to its low storage capacity,high price,poor stability,and slower catalytic kinetics,these disadvantages have limited its wide applications.In this paper,we hope to design catalysts from the following two aspects.In terms of optimizing the structure,we choose the nanometer dimension of carbon materials to increase the specific surface area of catalyst,and we also reduce the size of Pt nanoparticles to improve the utilization rate of Pt by an appropriate reduction method.In terms of optimizing chemical composition,we obtain Pt-M alloy or bimetallic oxides by doping cheap transition metal which provid a strong interfacial interaction to change the electronic structure of Pt nanoclusters surface.Finally,we successfully synthesize a multicomponent catalyst with excellent performance,and it is exceeded Pt-based catalytic materials reported so far.Now,here are two following aspects in the current research work.1.Promoting Effect of Heterostructured NiO/Ni on Pt Nanocatalysts toward Catalytic Hydrolysis of Ammonia BoraneThe multicomponent compound catalytic material is defined as Pt@NiO/Ni-CNT.With CNT as one-dimensional carbon carrier,loading a layer of NiO nanoparticles uniformly,followed by hydrogen reduction to heterostructure NiO/NiNPs,loading a layer of ultra-small Pt nanoclusters,in which Pt Ni is an alloy,through three steps reactions.Optimizing the chemical composition,the catalytic activity of Pt@NiO/Ni-CNT is greater than Pt@NiO-CNT and Pt@Ni-CNT with NiO or Ni alone.TOF?the turnover frequency of catalytic reactions?is 2665 mol _H2·mol _Pt^-1·min^-1 and activation energy is 24.9 k J·mol^-1.Catalytic kinetics studies have shown that the chemical composition and structural characteristics of Pt@NiO/Ni-CNT synergistically promote the oxidative clearage of H-O bond in attacked H₂O?rate-determining step?,thus promoting the hydrolysis rate of ammonia borane dynamically.2.Promoting Effect of Heterostructured?NiO/FeO_X?_M on Pt Nanocatalysts toward Catalytic Hydrolysis of Ammonia BoraneThe multicomponent compound catalytic material is defined as the Pt@?NiO/FeO_X?_3:1-CNT.The presence of heterostructural?NiO/FeO_X?_3:1 NPs is loaded on one-dimensional CNT,followed by hydrogen reduction to load a layer of ultra-small Pt nanoclusters,the chemical composition is optimized.The catalytic activity is higher than single or two component catalytic materials,with a high TOF of 2727.11mol _H2·mol _Pt^-1·min^-1 and a low activation energy of 26.99 k J·mol^-1.D₂O isotope experiments and Na OH simulated experiments had proved that the oxidation clearage of H-O bond in attacked H₂O is the rate-determining step of hydrogen evolution reaction.The strong interfacial interaction between two kinds of metal oxides accelerats the adsorption of reactants,which improves the rate of hydrogen evolution.In summary,we have designed multicomponent composite catalytic materials theoretically,and proved they have high catalytic efficiency.The method of rationally design hybrid nanocatalysts we provided can open up new innovative ideas for researchers of catalytic materials.