Simplifying the creation of iron compound inserted, nitrogen-doped carbon nanotubes and its catalytic application

The applicability of metals or their compound inserted, nitrogen-doped carbon nanotubes is blocked by the production although that its unique properties are outstanding in many fields. In this report, a synthetic strategy is developed to carbonize melamine in a CaCl2/FeCl3 molten salt medium and to prepare uniform iron or iron compound (including Fe3O4, Fe3C and Fe) inserted nitrogen-doped carbon nanotubes. The mechanism study of forming Fe3C@NCNTs find that the nanotubes with uniform structure are obtained from graphite sheets, which are formed at a relatively low temperature, and then the obtained graphite sheets transfer to tube shape with the catalysis of Fe at high temperature. The high catalytic activity of Fe3C@NCNTs is demonstrated by an onset oxidation potential of 0.27 V (vs. RHE) in the hydrazine oxidation reaction and an onset potential of 0.96 V (vs. RHE) for the oxygen reduction reaction. Based on DFT calculations, the good catalytic activity of Fe3C@NCNTs may be related to the decreased local work function on its surface. Fe3C@NCNTs also exhibit an enhanced reaction kinetics at higher potential, which make it a promising bifunctional catalyst for direct hydrazine fuel cells. Herein, highly efficient Nitrogen-doped carbon nanotubes filled with Fe3C nanorods was developed in CaCl2/FeCl3 molten-salt medium as HzOR and ORR electrocatalysts. [Display omitted] •Uniform Fe3C@NCNTs were prepared in CaCl2/FeCl3 molten salt.•Iron compound including Fe3O4, Fe3C and Fe were inserted NCNTs.•Fe3C@NCNTs exhibit good catalytic activity for HzOR and ORR.