Preparation Of Nanofiber Electrocatalytic Materials And Their Application In Energy Devices

Carbon peaks,carbon neutrality is an energy revolution.As a key supporting technology for this energy revolution,Fuel cells have attracted worldwide attention.However,the kinetics of their cathodic reactions are sluggish,and the electrocatalytic reactions rely heavily on noble metal catalysts,which largely hinder their practical applications.Therefore,the development of highly active and low-cost cathode electrocatalysts is a critical step to facilitate the commercialization of fuel cells.Nanofibers（NFs）,as a new type of catalyst support,possess tunable microstructure and large specific surface area,which are beneficial to the exposure of active sites and gas-liquid transport,thereby greatly improving the device performance.In addition,thanks to electrospinning,an economical and environmentally friendly synthesis method,high-throughput production of nanofiber electrocatalytic materials is expected.Based on this,this thesis focuses on the preparation of transition metal oxygen reduction（ORR）electrocatalysts and the construction of three-dimensional porous catalytic layer structures.catalytic material.The main research results and innovations are as follows:（1）A highly active and highly stable fluorinated nanoparticle carbon nanofiber material was synthesized.Iron and cobalt fluoride bimetallic nanoparticles distributed on carbon nanofibers were prepared by a strategy of fluorine doping and melamine-assisted pyrolysis.The fluorination process increases the charge density of the bimetallic sites and optimizes the adsorption of oxygen;the melamine-assisted pyrolysis increases the degree of graphitization of the carbon matrix and improves the durability.The synergistic effect of the two enables FeCoF@CNFs-M to obtain a half-wave potential of804 mV under the condition of 0.1 M HClO₄;the power density of the proton exchange membrane fuel cell device reaches 575 mW cm^-2.More importantly,the highly graphitized carbon nanofibers enhance the electrical conductivity and stability of the bimetallic catalyst,resulting in an ultra-stable support structure.The voltage of the fuel cell remained stable after 110 hours.（2）A non-pyrolytic self-supporting COP-based nanofibrous membrane material was developed.In order to explore the performance of non-pyrolytic catalysts with well-defined active sites in Zn-air flow batteries,organic covalent polymers（COPs）were grown in situ on the surfaces of nanofibers combined with the three-dimensional porous framework provided by nanofibers.form a core-shell structure.The high aspect ratio of the nanofibers and the topology of the COP material can expose the active sites to the maximum extent,and a three-dimensional conductive network can be constructed by filling the conductive carbon material through the core layer.It solves the problems of stacking buried active sites and poor conductivity of COP materials.The resulting self-supporting electrocatalytic material exhibits a power density of 228 mW cm^-2 in a zinc-air flow battery and can operate stably for over 1000 hours and 7500 cycles at a current density of 10 mA cm^-2.At the same time,the material has excellent tensile properties,the tensile strength can reach 8.7 Mpa,and it can withstand the tensile strain of 28%of its own body length,showing a good application prospect.