Atomic Iron Coordinated by Nitrogen Doped Carbon Nanoparticles Synthesized Via a Synchronous Complexation-Polymerization Strategy as Efficient Oxygen Reduction Reaction Electrocatalysts for Zinc-Air Battery and Fuel Cell Application

Developing atomic transition metal coordinated by nitrogen doped carbon (M-N-C) eletrocatalysts for oxygen reduction reaction (ORR) is critical to achieve low cost metal-air batteries and fuel cells. Herein, a general method of synthesizing M-N-C was developed via a synchronous complexation-polymerization strategy, in which nitrogen-containing ligand was coordinated with specific transition metal ions and diamino aromatic compound was simultaneously polymerized by the metal ion as initiator; by the following pyrolysis in a molten NaCl bath, M-N-C was finally synthesized. Fe-N-C was synthesized by this strategy using 2, 4, 6-Tri (2-pyridyl)-1, 3, 5-triazine (TPTZ) as ligand for FeCl2 and 1, 8-Diaminonaphthalene (DAN) as monomer of polymerization. Results demonstrate that introducing DAN into TPTZ-Fe2+ significantly affect the derived carbon structure and electrochemical performance of corresponding Fe-N-C. The Fe-N-C prepared by TPTZ and DAN with the molar ratio of 1:1 shows excellent ORR activity and durability, whose initial half-wave potential is 0.90V in 0.1 M KOH and 0.80V in 0.5 M H2SO4 respectively, after 10K cycles, the potential is only 14mV loss in 0.1 M KOH and 20mV decay in 0.5 M H2SO4 . And the ORR performance as cathode was further proved by a single practical Zn-air battery with a maximum power density of 192 mWcm -2 and a specific capacity of 800 mAh gZn-1 , much higher than 137 mW cm-2 and 735 mAhgZn -1 of the same loading of commercial Pt/C catalyst and proton exchange membrane fuel cell with a high power output of 640 mW cm-2 . Attributed to the vast variety of ligands, metal ions and polymerizing monomers, this strategy provides a flexible platform of synthesizing advanced M-N-C catalysts, compared with previously reported methods.