Preparation Of Ni/TiN And Au(Ni)/TiN@Ti Composite Micro/Nanostructures And Catalytic Activity To Metaborates

Hydrogen energy has significant advantages of high energy efficiency ratio and environmental friendliness,and is recognized as a green and efficient new energy with broad application prospects.The large-scale development of hydrogen economy still faces two challenges:the acquisition of high-quality and cheap hydrogen sources,and the controllable application of hydrogen.In recent years,various hydrogen production and storage strategies have been put forward,among which hydrogen storage and hydrogen release of compounds have attracted extensive attention from all walks of life.Ammonia borane（NH₃BH₃,AB）,with theoretical hydrogen content of 19.59%can exist in solid state at room temperature,and has stable physicochemical properties with non-toxic and non-flammable feature.It can release hydrogen in a controllable way via catalytic hydrolysis or alcoholysis,and has been regarded as an ideal medium for hydrogen storage.At present,most of the reported catalysts involve precious metals.Despite of excellent catalytic performence,the high prices limit their large-scale commercial use.Therefore,it is of great theoretical significance and application value to seek efficient and cheap new catalysts for the stabilized and controlled release from the related compounds.As the part of the research content for national natural science fundation project（No.21576073）,this dissertation mainly focuses on the preparation and evaluation for titanium compound（titanium nitride,titanium oxide）loaded transition metal catalyst,fabricating and characterizing multi-shaped titanium nitride,titanium oxide,and evaluating their catalytic ability.Moreover,the the electrochemical behavior of the titanium nitride catalytic electrodes in borate solution has also beeen deeply probed.1.Controllable preparation,characterization and their catalytic hydrogenation of amaborane water for Ni/TiN nanotubesIn the concentrated alkali solution,cellular titanium oxide nanotubes（TiO₂-NTs）were prepared by hydrothermal synthesis,and then thermally reduced to titanium nitride nanotubes（TiN-NTs）by nitriding method;X-ray diffraction（XRD）,field emission scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,spectroscopy（EDS）and fully automated microporous analyzer（SET）were used to analyze the phase and morphology of the product.The results showed that the TiO₂-NTs have a diameter of 100-200 nm and a specific surface area of 273.156 m²/g.After high-temperature nitridation,the diameter of TiN-NTs reached 120-200 nm,the specific surface area was 40.922 m²/g,and the surface of the nanotubes was showed irregular porous.structure.Ni nanoparticles（NPs）with a diameter of about 120 nm were synthesized by hydrazine reduction method.The prepared Ni nanoparticles were loaded on the surface of porous TiN-NTs by ultrasonic impregnation load and in-situ loading method respectively.The results showod that nano-Ni can be uniformly loaded on TiN-NTs by in-situ reduction process,while the original porous structure remains unchanged.Ni-Ni and supported Ni/TiN-NTs were used as catalysts for interpreting hydrogen in AB water,and it was found that the catalytic activity of Ni/TiN-NTs was better than that of nano-Ni.Moreover,at 20°C and 25°C,the catalytic AB hydrolysis reaction of Ni/TiN-NTs has an induction period.After the temperature increased,the induction period gradually disappeared and the hydrogen release rate also increased significantly.After 5 cycles,Ni/TiN-NTs still maintain 73%initial catalytic activity.2.Preparation and characterization of titanium matrix composite microstructure electrodeA titanium oxide nanotube array（TiO₂@Ti-NTAs）was grown on a titanium metal sheet by anodization,and a titanium nitride nanotube array（TiN@Ti-NTAs）was obtained by nitridation.The phase and morphology of the electrode were analyzed by means of XRD,SEM and EDS.The results showed that the diameter of TiO₂@Ti-NTAs was 150 nm and the wall thickness was 20 nm.After nitriding,the diameter of the tube was reduced to 130 nm and the wall thickness was increased to 30 nm.And the nanotube arrays collapsed slightly.A multi-current step method was used to uniformly deposit metal Ni on the surface of TiN@T-NTAs to obtain a porous Ni/TiN@Ti-NTAs electrode.Ti,TiO₂@Ti,TiN@Ti,Ni/TiN@Ti,Ni/TiN@Ti-NTAs were used as substrates to deposit a thin layer of noble metal Au of controlled thickness by plasma sputtering to form Au/Ti and Au/TiO₂@Ti,Au/TiN@Ti,Ni/TiN@Ti and Au（Ni）/TiN@Ti-NTAs nanotube array composite structure electrode system,and the morphology of Ni and Au metal layers were analyzed.3.Electrochemical behavior of titanium-based composite microstructure electrode in sodium metaborate alkaline solutionThe five composite electrodes of Au/Ti,Au/TiO₂@Ti,Au/TiN@Ti,Ni/TiN@Ti and Au（Ni）/TiN@Ti-NTAs were used as cathodes,with graphite counter electrode and Saturated calomel reference electrode to constitute a three-electrode system.The electrochemical behaviors of the NaOH solution and the NaBO₂ alkaline solution were separately studied.And the pulse power source and the cation exchange membrane were added,and the conditions such as electrolysis time,voltage and pulse ratio were modulated appropriately.The change of the above electrodes was further explored.It was confirmed that the reduction mechanism of BO₂^-should belong to the indirect electrocatalytic（EC）reaction,and the reasons for the experimental results were analyzed and inferred.