Synthesis And Electrochemical Properties Of Metal-Organic Framework Derived Materials

The development of clean energy technology is the key to solve energy and environmental problems.Electrochemical energy storage and conversion technology,represented by lithium/sodium-ion battery and electrocatalytic oxygen evolution reaction,has been widely concerned because of its high conversion efficiency and environmentally friendly advantages.Although the reaction mechanism is different,the electrochemical active materials with high reactivity and excellent stability are of great importance to improve the performance of these electrochemical reactions.Therefore,it is very significant to design and synthesize electrochemical active materials with fine structure for the development of electrochemical energy storage and conversion technology.Metal-organic framework is a class of functional porous materials formed by self-assembly of metal centers and organic ligands.This paper develops a method for preparing multifunctional electrode materials using metal-organic framework materials as precursors,which fully reflects the high adjustability and universality of the metal-organic framework materials template method.In addition,the electrochemical performance of the electrode materials in oxygen evolution reaction and lithium/sodium ion batteries was studied.The main results are as follows:(1)A facile template-engaged strategy is adopted to fabricate hollow microspheres derived from a Co-MOF.After a thermally induced selenylation process under an argon atmosphere,the Co-MOF is successfully converted into CoSe2 microspheres at different temperatures.Notably,the hollow structure affords space for fast mass transport and charge transfer between the electroactive materials and the electrolyte.What's more,the well-distributed CoSe2 nanoparticles attached on the microspheres offer abundant electroactive sites for the OER.The optimized CoSe2-450 microspheres display excellent OER electrocatalytic performance in 1.0 M KOH aqueous solution,exhibiting 10 mA cm-2 at overpotential of 330 mV with a small Tafel slope of 79 mV dec-1,even superior to those of a commercial IrO2 catalyst.(2)Cobalt-nickel alloy nanoparticles coated with nitrogen-doped carbon were successfully prepared by one-step heat treatment using bimetal-organic framework as the template.The optimized graded Co2Ni@NC nanoparticles combine nanostructure engineering and component modulation together,with fast mass transfer capabilities and rich synergistic active sites.Remarkably,the optimized Co2Ni@NC exhibits a small overpotential of 310 mV to achieve a current density of 10 mA cm-2 and an excellent long-term stability in alkaline electrolyte.Furthermore,the underlying synergistic effect mechanism of Co-Ni model has been pioneeringly elucidated by density functional theory calculations.(3)In this work,with rationally designed metal-organic framework/graphene oxide as a precursor,a nitrogen doped ZnSe/reduced graphene oxide(rGO)composite was successfully prepared via a carbonization-selenylation procedure.On the one hand,the unique nitrogen-doped ZnSe polyhedron enriches the active sites for storing Li/Na ions.On the other hand,the rGO network can not only act as a conductive substrate to promote electron transport,but also effectively alleviate volume expansion during cycling.The optimized N-ZnSe@rGO delivers an ultrahigh capacity(836 mAh g-1 at 100 mA g-1)and displays ultrahigh stability(464 mAh g-1 at 2000 mA g-1 after 1000 cycles)as the anode in LIBs,while it shows a reversible capacity of 285 mAh g-1 after 500 cycles at 300 mA g-1 for SIBs.(4)With rationally designed hierarchical metal-organic framework(MOF)@MXene as a precursor,a novel sandwich-like CoP-NC@Ti3C2Tx composite has been successfully fabricated by the following phosphorization reaction.The well-designed sandwich-like composite effectively supports the easy access to electrolyte,facilitate the Li/Na ion transportation,and protect the active material from pulverization upon long cycling.As anode material for LIBs,the CoP-NC@Ti3C2Tx composite exhibits remarkable electrochemical performance with high-rate capability(147.8 mAh g-1 at 2000 mA g-1;245.6 mAh g-1 at 100 mA g-1)and ultralong cycling life(2000 cycles with a capacity retention over 100%).For SIBs,it delivers a discharge capacity of 101.6 mAh g-1 at a current density of 500 mA g-1 after 500 cycles.In addition,the electrochemical reaction kinetics and Li-migration kinetics of the CoP-NC@Ti3C2Tx composite has been pioneeringly illuminated by pseudocapacitive behavior calculation and density functional theory(DFT)computations,respectively.