Study Of Preparation And Properties Of MOFs-derived Cobalt-iron-based Trifunctional Electrocatalysts

In order to safely and efficiently utilize the uncoordinated green energy in space and time（such as solar energy,water energy,wind energy,etc.）,it is urgent to develop energy conversion and storage systems that are conducive to environmental protection and energy conservation,such as zinc-air cells,hydrazine fuel cells and electrolytic water driven by electrocatalytic reactions such as oxygen reduction reaction（ORR）,oxygen evolution reaction（OER）,hydrazine oxidation reaction（Hz OR）and hydrogen evolution reaction（HER）.However,the multifunctional electrocatalysts required for these reactions and devices still suffer from high cost,difficult synthesis,and insufficient catalytic activity and durability.Today,metal-organic frameworks（MOFs）derived materials enable the controllable synthesis of the structure and function of catalyst components,showing great application prospects of energy conversion and storage.Therefore,this thesis takes MOFs derivatives as the research object.Materials with good ORR/OER/HER and Hz OR catalytic performance were prepared by adjusting the precursor composition and synthesis conditions,and their applications for zinc-air batteries,direct hydrazine fuel cells and electrolyzed water were further explored.The main research contents are as follows:（1）A trifunctional electrocatalyst derived from zeolite imidazolate frameworks（ZIFs）was synthesized by self-assembly at room temperature and pyrolysis at high temperature,and the catalyst was composed of 1D N-doped carbon nanotubes modified 3D cruciform carbon matrix（NCNTs//CCM）and Co_5.47N and Co₇Fe₃（Co Fe N）heterostructure.Electrochemical tests showed that Co Fe N-NCNTs//CCM exhibited excellent activities for the trifunctional electrocatalysis of ORR,OER and HER.The Zn-air battery and overall water-splitting cell assembled with this catalyst as the air electrode also exhibited excellent performance;In addition,a self-powered overall water-splitting system for Zn-air batteries based on Co Fe N-NCNTs//CCM successfully realizes a dynamic combination of integrated devices.（2）According to the previous chapter,the Cu-doped Fe Co/Co electrocatalytic material was synthesized by using similar methods.Due to the regulation of metal doping and heteroengineering,Cu-Fe Co/Co/NC exhibits excellent electrocatalytic activities for ORR,Hz OR,and HER.Direct hydrazine fuel cells assembled with Cu-Fe Co/Co/NC show higher open circuit voltage and peak power density,and the overall coupled hydrazine decomposition（OHz S）system in alkaline seawater can be driven at lower voltages Seawater electrolysis.Additionally,self-assembled direct hydrazine fuel cells were used for self-powered OHz S,demonstrating the great potential of this electrocatalyst in energy storage and conversion devices.