Construction And Electrocatalysis Of One-dimensional Nanostructured Nanomaterials

Because of the growing demands for energy and depletion of the traditional fossil energy,the search for clean and renewable energy has gradually become the frontier and hotspot in the energy field.Hydrogen is considered as an ideal clean energy due to its high energy density,abundant sources and simple preparative techniques.Hydrogen production technology through water electrolysis has become one of the most promising hydrogen production methods at present because of its low cost,simple equipment,and pollution-free by-products.However,the high cost of noble metal catalysts limits the development of water electrolysis for hydrogen production.Therefore,there is an urgent need to find a cheap,efficient,and stable electrocatalyst to accelerate the large-scale application of water electrolysis for hydrogen production.In this thesis,four kinds of special one-dimensional nanostructured fibers with high electrocatalytic activity were constructed by electrospinning technology.The morphology,composition,structure and electrocatalytic performance of these materials were studied in detail.Further,the formation mechanisms of the new materials were clarified,and new technologies for their construction were established.The specific research contents are as follows:（1）[Ni/C]@[Co/C]coaxial nanofibers（with Ni/C as core and Co/C as shell）were designed and constructed by the coaxial electrospinning technology.Due to the high electrical conductivity of the carbon substrate,the regulation of the metal particle arrangement by the coaxial structure,and the synergistic effect of the bimetals,the optimized material exhibits excellent electrocatalytic activity for hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）in alkaline solution.When the current density is 10 m A cm^-2,the overpotential is 234 and 370 m V for HER and OER,respectively.The coaxial nanofibers exhibit better electrocatalytic performance than the counterpart non-coaxial nanofibers with same compositions,fully demonstrating their structural superiority.（2）[Co/C]@[Ni/C]coaxial nanofibers（with Co/C as core and Ni/C as shell）were prepared by the coaxial electrospinning technology.The constructed coaxial nanofibers also exhibit excellent HER and OER performances in alkaline solution.The coaxial nanofibers also display better electrocatalytic performances than the counterpart non-coaxial nanofibers,further demonstrating their structural advantages.It is also proved that the arrangement of the components has a certain influence on the electrocatalytic performance.（3）Mo₂C/Co/Co O nitrogen-doped hollow carbon nanofibers（NHCNFs）were designed and prepared by the coaxial electrospinning technology.The material has a large electrochemical active area,providing more exposed active sites.At the same time,the doped Co components can adjust the electronic structure of Mo₂C,and the synergistic effect between them can effectively improve the electrocatalytic performance of the material.The optimized material exhibits excellent HER performance with a low overpotential of 143m V at a current density of 10 m A cm^-2,and has superior cycling stability.（4）Flexible self-supporting[Mo₂C/C]@[Mo₂C/C]wire-in-tube nanofibers were designed and prepared by the coaxial electrospinning technology.The large specific surface area of the material increases the exposure of active sites.At the same time,the design of the double-layer carbon layer can increase the electrical conductivity of the material and enhance the synergistic effect of the active sites in the electrochemical process.In addition,the self-supporting electrode can avoid the internal resistance created by the use of binders during the reaction process,thereby improving the eletrocatalytic activity of the material.The optimized material exhibits excellent HER catalytic performance with a low overpotential of 164 m V at a current density of 10 m A cm^-2,and also manifests excellent flexibility and stability.The four constructed carbon-based non-noble metal special one-dimensional nanostructured materials all have outstanding electrocatalytic performances,and the obtained innovative research results provide new ideas for the development of other highly efficient and inexpensive electrocatalysts.