Based On MOFs To Co-hollow/core-shell@Graphene Composite Materials:Preparation,Characterization And Properties

In this paper,metal organic compounds?MOFs?and zeolitic imidazolide frameworks?ZIFs?were used as pyrolytic precursors,and the metal?0?/metal oxides-carbon shells and metal?0?/metal oxide-carbon shell-graphene were synthesized by solvothermal-pyrolysis method.The spherical zeolitic imidazolide frameworks?ZIFs?structure was prepared by one-step solvothermal method.Using ZIFs as the pyrolysis precursor,and the nano-hollow spheres were formed by pyrolysis.We investigated their hydrogen production and anode materials performance in lithium ion batteries?LIBs?,all of them showed good performance.Firstly,Co-based metal organic frameworks?MOFs?with two shapes were used as pyrolysis precursor to synthesize multilayer core-shells composites loaded on reduced graphene oxide?rGO?sheets.The core-shell structures were obtained by the formation of cores from metal ions and carbon shells from carbonization of ligands.Controllable oxidation of Co cores to CoOx shells generated multilayer core-shell structures anchored onto the surface of rGO sheets.The N-doped composites were obtained by adding poly vinylpyrrolidone.The multilayer core-shells composites exhibited superior catalytic activity toward hydrogen generation compared to their single layer counterparts.By using the N-doped multilayer composites,high hydrogen generation specific rate of 5560 m L?min-1?g Co-1 was achieved at room temperature.The rGO sheets in composites improved their structure stability.These catalysts exhibited high stability after used five cycling.This synergistic strategy proposes simple,efficient,and versatile blue-prints for the fabrication of rGO composites from MOFs-based precursors.Secondly,a Co₃O₄ hollow sphere composite covered by carbon?CHS@C?was synthesized through pyrolysis of Co-ZIFs spheres.The hollow spheres structures of Co₃O₄ were covered by graphene sheets as carbon shells?CHS@CG?.The C from the graphene sheets in CHS@CG improved the electrical conductivity and structure stability of CHS@CG.By the electrochemical performance tests in 400 cycles,the reversible specific capacity reaches up to 831 m A?h?g–1 at 0.2 C current rate.In the constant charging and discharging process,coulomb efficiency reaches nearly 100%,exhibiting a good reversible cycle.The synthesis approach may be used in the design and preparation novel electrode materials of LIBs.