One-dimensional MOFs-based Non-noble Metal Doped Carbon Nanotubes And Their Electrocatalytic Properties

With the rapid development of global economy,the problems of energy and environment are becoming increasingly serious.The development of clean and efficient energy conversion system had become a research hotspot in recent years.Fuel cell is a new type of cells that can convert chemical energy into electric energy and achieve no carbon emission.Its high efficiency and energy saving characteristics can effectively alleviate energy and environmental problems.However,most catalysts used in fuel cell were difficult to mass produce due to insufficient energy density,insufficient stability,or high cost.Therefore,the preparation of a cheap and efficient electrocatalyst used in fuel cells is the key to solve the energy and environmental problems.Metal organic frameworks are made up of inorganic metal ions and organic ligands by covalent bond or a covalent bond formed by self-assembly with uniform porous structure of the nanocrystalline material,with high specific surface area and pore structure,it can greatly increase the contact area with other material.In order to gain highly active,metal organic frameworks is widely applied to the battery and catalytic,etc.As a typical one-dimensional material synthesis method,electrospinning technology has the advantages of low cost,high specific surface area,controllable composition and structure of the synthesized fiber,and electrospinning technology had been widely used in commercial production.Especially for the nanostructure units,it shows a good assembly effect,which is beneficial to further improve the properties of the materials.Therefore,in this paper,the assembly effect of electrospinning technology is combined with the synthesis method of metal-organic frameworks,and one-dimensional non-noble metal electrocatalysts with different morphologies,structures and components are prepared by different processing methods.The main research results are as follows:1.Bifunctional electrocatalysts with high efficiency hydrogen evolution（HER）and oxygen evolution（OER）reactions were prepared by using a multi-step synthesis strategy.Electrocatalysts were prepared by indirect spinning method and high temperature firing ZIF-8@ZIF-67 nanotubes and its derivative Co₃O₄ nitrogen doped porous carbon nanotubes,and further through the water thermal response in the hybrid carbon nanotubes synthesized on the surface of ultra-thin sliced MoS₂nanotubes,at last,by converting Co₃O₄ phosphating reaction CoP,the CoP with core-shell structure was prepared and MoS₂ doped porous carbon nanotubes（NCT@CoP@MoS₂）.By adjusting several reaction parameters,the composition and structure of NCT@CoP@MoS₂ nanotubes were regulated,and the electrocatalytic performance of the nanotubes for HER/OER was studied.Due to the advantages of multilevel pore structure and composition,the synergistic effect between compared with other contrast samples,the NCT@CoP@MoS₂ nanotubes in the process of HER and OER showed a low potential and smaller tafel slope and cycle stability,proved highly active and high structure stability of the catalyst.Further,NCT@CoP@MoS₂was simulated at the same time as the cathode and anode electrolysis of water splitting device,the structure of the experiment indicate that the electrode material in the current density of 10 m A·cm^-2 provides a low battery voltage of 1.57 V,in 40 hours of only 5%of the whole water decomposition in the process of current density light attenuation,it shows that the NCT@CoP@MoS₂ electric catalyst with high stability.2.A highly efficient iron/nitrogen doped carbon nanotubes electrocatalyst for oxygen reduction reaction was prepared.We had successfully synthesized Zn/Fe bimetallic zeolite imidazole framework on the surface of polyacrylonitrile nanofibers by using electrospinning nanofibers as self-sacrificing templates.One-dimensional hollow carbon nanotubes supported iron catalysts had been synthesized by etching and one-step pyrolysis.In the process of pyrolysis,the sublimation of zinc provides a large number of vacancies and defects to the material,which was conducive to the exposure of iron atoms to the electrolyte.The reduced iron atoms coordinate with the nitrogen atoms near the defects to form Fe-N active sites,showing high catalytic activity for oxygen reduction reaction.In the experimental process,we explored the influence of different precursor ion molar ratio,calcination temperature and acid etching treatment on the catalytic activity of the sample.Due to the porous structure and large specific surface area of MOFs derived materials,as well as the common advantages of one-dimensional structure and components,the synthesized NCT@Zn₁₀₀-Fe₁₀ nanotubes had excellent catalytic activity and good stability for oxygen reduction reaction in alkaline solution.In addition,NCT@Zn₁₀₀-Fe₁₀ showed good methanol resistance in methanol solution and is expected to be widely used as a catalyst for methanol fuel cells.