Characterization And Energy Storage Applications Based On Novel Metal-organic Frameworks Derivatives

Metal-organic framework materials(MOFs)are a new class of crystal materials formed by organic ligands and metal or metal clusters connected by coordination bonds,which have received more and more attention in recent years.In addition,compared to complex and uncontrollable traditional synthesis methods,some functional materials such as porous carbon materials,metal oxides and their composite could be spontaneously derived from MOFs under proper regulation.These derivatives could also inherit many advantages of MOFs to show novelty.MOFs and their derived structures always demonstrate the virtues of high porosity,large specific surface area and strong structural tunability,etc.Accordingly,they have been widely applied in gas storage and separation,catalysis,energy storage and conversion,etc.This paper focused on the preparation and characterization of novel MOFs and their derived structures,and energy storage applications of the derivatives were aslo studied detailedly.We have successfully prepared novel bimetallic MOFs(Ni(II)-MOF-5)and rod-shaped lanthanide MOFs(Ce-BTC).Especially,for the first time,Ce-BTC(ST)microrods were synthesized by a solvothermal method.At the same time,two porous composite materials(Ni@C)were simply prepared from the bimetallic Ni(II)-MOF-5s,and we also used two rod-shaped Ce-BTCs as precursors to obtain CeO2@C composites by a two-step calcination method.These products retained rod-like morphologies,which composed of a CeO2 matrix with partial graphitized carbon well dispersed.These new Ni@C composites have been characterized efficiently to have good structural properties such as hierarchical porosity,large specific surface area,component uniformity and purity,which are potential for energy storage applications.Accordingly,we have studied these materials to apply in hydrogen storage and supercapacitors.Notably,Lithium borohydride(LiBH4)as a very promising lightweight hydrogen-storage material possesses very high theoretical gravimetric hydrogen-storage capacity of 18.5 wt.%.The optimized synergistic effects of nanoconfinement-destabilization of porous carbon and catalysis of well-dispersed Ni nanoparticles in Ni@C-1 could greatly lower the onset temperature and improve dehydrogenation kinetics of LiBH4.Meanwhile,Ni@C-2 consisted of more uniform fine metallic Ni nanoparticles and more turbostratic graphitic shells,also showed a higher degree of graphitization.Due to these features,their electrodes had excellent capacitor retention under different current densities and cycle life stability,which demonstrated the characteristics of the ideal electric double layer capacitor(EDLC).The prepared novel CeO2@C composites with regular rod-like micro-/nanostructures also had strong functionality.The CeO2@C(ST)contained hierarchically mesoporous structures and more graphitized carbon,which enhanced the ions diffusion and electron transfer ability.The electrode material exhibited good conductivity to obtain excellent electrochemical performances of pseudocapacitor.