Study On The Preparation Of Two-dimensional CoFeNi-Based Metal-Organic Frameworks And Its Performance In Oxygen Evolution Reaction

Due to the rapid increase in the consumption of traditional fossil fuels and the shortage of energy and environmental degradation,the need for sustainable renewable energy technology development is becoming increasingly urgent.Known new energy technologies include carbon dioxide reduction,metal-air batteries,and electrolyzed water technologies,all of which have an oxygen evolution reaction process.However,the kinetics of the oxygen evolution reaction involving the four-electron transfer process is relatively slow,which requires the development of a more efficient catalyst for the oxygen evolution reaction.Commercialized oxygen evolution reaction catalysts include Ru O₂ and Ir O₂.Their performance and stability have been recognized by the market,but due to their small reserves and high price,they have greatly restricted their widespread use.With its adjustable porosity,high specific surface area,and abundant metal centers,metal organic framework materials have become a new type of electrocatalyst for oxygen evolution reaction.However,most metal-organic frameworks are non-conductive,and usually use high-temperature calcination to form carbon materials or grow on conductive substrates for oxygen evolution reaction.These methods are cumbersome and costly,which limits their practical application.The ultrathin shape of the two-dimensional metal organic framework materials greatly reduce the path of electron transfer,thus reducing the electrical conductivity requirements of the electrocatalyst.This type of material has great potential for electrocatalytic oxygen evolution reaction.This paper takes the ultrathin metal organic framework as the starting point,and improves the electrocatalytic performance of the metal organic framework by adjusting the electronic structure of the material.The specific research content includes the following two aspects:（1）Synthesis of ultrathin trimetallic organic framework by three-layer method.SEM,TEM,AFM and other methods confirmed that the resulting material was ultra-flaky,with a thickness of 8-9 nm.By simply changing the proportion of each metal element in the raw material,the content of the three metals in the two-dimensional metal organic framework is adjusted.The optimized trimetallic organic framework（Ni₃Co₁）₃Fe₁-MOFs showed excellent electrocatalytic oxygen precipitation performance in alkaline electrolytes.The current density of 10 m A cm^-2was only 245 m V,and the Tafel slope was 50.9 m V dec^-1,and the electrochemical stability is also relatively good.After 30,000 s test,the current density decreased by only 9%.Further with the help of XPS,XRD and Raman technology,we found that the active species of the trimetallic organic framework nanosheets during the oxygen evolution reaction may be hydroxides and oxyhydroxides.This research provides an idea.（2）The ultrathin trimetallic organic framework is synthesized by microwave method,and the trimetallic organic framework nanosheets can be synthesized in 30 minutes,which greatly shortens the synthesis time.The materials confirmed by SEM,TEM and AFM,which are ultra-flaky structures with a thickness of 2.12 nm.With the help of XPS,in the microwave reaction process,a certain amount of cobalt vacancies can be generated,resulting in changes in the electronic structure of the trimetallic organic framework nanosheets,thereby reducing the reaction barrier,and ultimately making the ultrathin trimetallic The electrocatalytic oxygen evolution reaction performance of the organic framework has been improved.Among them,after optimizing the metal ratio,the overpotential of MW-Ni₄Co₄Fe₂-UMOFNs synthesized by microwave method at 10 m A cm^-2 is only 243 m V,the slope of Tafel is 48.1 m V dec^-1,and the electrochemical stability is also comparative Well,after 10 hours of testing,the current density decreased by only 8%.This work not only provides a method for the rapid synthesis of ultrathin metal organic frameworks,but also demonstrates the strategy of adjusting the electronic structure in metal organic frameworks by microwave action.