Study Of Derivatives Of Metal-Organic Framework For Oxygen Evolution Reaction

Metal-organic frameworks are crystals,which are composed of organic ligands and metals.Its adjustable porosity,opened channels,and high specific surface areas are of great significance for rapid mass transfer and improvement of catalytic performance.However,the activity of MOFs’derivatives is usually affected by factors,such as poor electronic conductivity,low exposure of active centers,and low intrinsic activity.Recent research results show that by designing the precursors of MOFs,adjusting the synthesis process,adding auxiliary components,optimizing the annealing temperature and atmosphere,etc.This thesis takes MOFs as the main research object,and aims to explore the synthesis of MOFs-derived electrocatalytic material systems by etching through cation exchange method,thereby improving the electrocatalytic performance of MOFs-derived materials.This paper provides a reference for the regulation of MOFs-derived electrocatalytic materials.The main research is as follows:1.Taking Co/MOFs as the research object,using double cation exchange method,annealing in air,synthesized Fe Ni CoO_Xhierarchical hollow nanocages（Fe Ni CoO_XHHNCs）for oxygen evolution reaction.The experimental results show that the synthesized Fe Ni CoO_XHHNCs with hierarchical hollow nanocages can not only increase the contact area,but also further shorten the ion diffusion length.In addition,the composition of polymetallic elements increases the interaction between electrons and the synergistic effect of metals.Due to these designs,FeNiCoO_XHHNCs have achieved excellent electrochemical properties,the overpotential is 248mV(10 mA cm^-2),the Tafel slope is 45.4 mV dec^-1.2.Taking Co/MOFs as the research object,using single cation exchange method and high temperature annealing in argon,Co_0.7Fe_0.3alloys are strong coupled with oxygen-enriched CoFe₂O₄(Co_0.7Fe_0.3/CoFe₂O₄)for oxygen evolution reaction.The high porosity of the synthesized Co_0.7Fe_0.3/CoFe₂O₄hollow nanocages can suppress the volume expansion during the reaction and increase the contact area between the electrocatalysts and the electrolyte.In addition,a large number of oxygen vacancies and interconnected network structures generated in CoFe₂O₄ can significantly improve electronic conductivity,thereby improving the electrochemical performance of OER.Co_0.7Fe_0.3/CoFe₂O₄ have achieved excellent OER properties,with the overpotential of 296 mV(10 m A cm^-2),and the Tafel slope of 51.6 mV dec^-1.