Preparation And Performance Of Single Or Multi-shelled Hollow Nano Materials

Hollow nanostructured materials and their composite structures have extensive applications in catalysts,super capacitors and lithium-ion battery electrodes etc.,due to their large specific surface area,low density and internal cavity.Compared with single shelled hollow structure,multi-shelled hollow structure exhibits unique properties and bright application prospect,owing to its unique internal spatial structure.The purpose of this paper is to prepare single and multi-shelled hollow nanomaterials and investigate their catalytic and electrochemical performance.Firstly,Ni/SiO₂ was prepared through in-situ thermal degradation for reducing the cost of catalyst and improving the catalytic activity.Double-shelled hollow silica spheres with large specific surface area and mechanical stability were selected as the support of Ni nanoparticles.Ni could be firmly attached to the surface of SiO₂ or embedded into the nanopores of SiO₂ shells with good dispersion.The as-sythesised catalysts are readily recycled and exhibit outstanding catalytic performance.The obtained catalysts can maintain high catalytic activity even with a high loading of 61.7%.After five cycles,the hydrolysis of ammonia borane can reach 94% within 9 min.Moreover,its catalytic performance remains outstanding,after the catalyst is placed in the air for two weeks,validating good chemical stability.Secondly,a series of three-shelled metal oxide spheres was prepared using hard template method.The ration of cobalt to nickel was optimized.The hollow nanoparticles were then applied as positive electrode of super capacitor to test its electrochemical performance.The resulting material has a uniform particle size with three-shelled architecture.Ni-Co_1.5-O electrode material exhibits superior capacitance(1884 F?g^-1 at 3 A?g^-1)and the corresponding value at 30 A?g^-1 can still reach 77% of that at 3A?g^-1.In addition,the prepared double-electrode asymmetric supercapacitor Ni-Co_1.5-O//RGO@Fe₃O₄ still retains 79.4% of its initial capacitance after 10000 cycles,delivering an energy density of 1541.5 Wh?kg^-1 at 505 W?kg^-1,and it still maintains a high energy density of 22.8 Wh?kg^-1 even at 7600 W?kg^-1.Finally,the hollow nanostructured material void@C-Fe₃O₄ was prepared by hard template method.The microspheres were then characterized and their electrochemical performance was tested.It was found that Fe₃O₄ was uniformly dispersed in the hollow carbon shell without agglomeration.In addition,void@C-Fe₃O₄ exhibits excellent performance as the negative electrode materials of lithium ion battery.At current density of 500 mA?g^-1,its capacity is 587 mAh?g^-1.After 100 cycles,its capacity decreased to 402 mAh?g^-1,and the Coulombic efficiency could still maintain 97.3%.This void@C-Fe₃O₄ electrode exhibit super high rate capability(583,508,425,322,209,146 mAh?g^-1 at 100,200,500,1000,2000,3000 mA?g^-1).When current density was reset to be 100mA?g^-1,the corresponding average capacity is 572 mAh?g^-1,remaining 98% of the original value.Double-shelled hollow nanometer-sized material void @C-Fe₃O₄@void@C-Fe₃O₄ has also been successfully prepared and its performance needs to be further studied.