Fangcai Zheng

Preparation and characterization of single phase γ-Fe nanopowder from cw CO2 laser induced pyrolysis of iron pentacarbonyl

Pure gamma-Fe particles were prepared from cw CO2 laser induced pyrolysis of iron pentacarbonyl. The synthesized particles were characterized by means of transmission electron microscopy, X-ray diffraction and vibrating sample magnetometer. The particle size ranged from 30 to 80 nm diameter and showed clear crystal habit of polyhedra. It is found that many planar defects, such as stacking faults and twins occurred in the gamma-Fe particles. The reason for the formation of defects is discussed. In addition, annealing experiments of the gamma-Fe ultrafine particles were carried out at 100-500-degrees-C and magnetic properties of the annealed powder were examined at room temperature. It is indicated that the gamma-Fe phase is stable at room temperature and the transformation of gamma-Fe to alpha-Fe starts at above 250-degrees-C.

Facile fabrication of highly porous Co3O4 nanobelts as anode materials for lithium-ion batteries

Highly porous Co3O4 nanobelts were successfully synthesized by using a hydrothermal technique, followed by calcination of the Co(OH)2 precursor. The as-prepared Co3O4 nanobelts were analyzed by scanning electron microscopy, X-ray power diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller methods. The electrochemical properties of porous Co3O4 nanobelts were examined by cyclic voltammetry and galvanostatic charge–discharge studies. Owning to the unique 2D structural features, the Co3O4 nanobelts exhibited a high specific capacity of 857 after 60 cycles at a current density of 100 mA g−1, and good cycling stability. These exceptional electrochemical performances could be attributed to the remarkable structural feature with a high surface area and large amounts of nanopores within the surface of nanobelts, which can provide large contact areas between electrolyte and active materials for electrolyte diffusion, improve structural stability and buffer volume expansion during the Li+ insertion/extraction processes.

Facile synthesis of MOF-derived ultrafine Co nanocrystals embedded in a nitrogen-doped carbon matrix for the hydrogen evolution reaction

Non-precious metal-based catalysts with low cost and rich reserves are emerging as promising alternatives for Pt-based catalysts for the hydrogen evolution reaction (HER). Herein, we reported a facile and large-scale strategy for Co nanocrystals embedded in a nitrogen-doped carbon matrix through direct carbonization of Co-based metal–organic frameworks (MOFs) in N2. After carbonization, the ultrafine Co nanocrystals are well dispersed in the nitrogen-doped carbon matrix. We further studied their electrocatalytic properties toward the HER in acidic media and found that the as-prepared catalyst exhibited enhanced catalytic activity and stability.

Facile synthesis of MOF-derived Mn2O3 hollow microspheres as anode materials for lithium-ion batteries

In this article, we report a facile and scalable route for the fabrication of Mn2O3 hollow microspheres by direct pyrolysis of Mn-based metal–organic frameworks at 450 °C with a heating rate of 10 °C min−1 in air. The effect of the heating rate on the morphology of the final samples has been also investigated. When evaluated as an anode material for LIBs, these Mn2O3 microspheres exhibited a reversible and stable capacity of 582 mA h g−1 after 60 cycles at a current density of 100 mA g−1. The improved capacity and excellent cycling stability of the as-prepared Mn2O3 microspheres could be attributed to the porous hollow structures, which can reduce diffusion length for lithium ions and electrons, and also can enhance structural integrity for buffering the volume expansion during the discharge/charge processes.