Synthesis of nanoporous structured iron carbide/Fe N carbon composites for efficient oxygen reduction reaction in Zn air batteries
Large scale industrial level applications of fuel cells and metal air batteries have called for the development of highly efficient and low cost oxygen reduction electrodes. Here we report the effective and simple preparation of iron carbide embedded Fe N doped carbon (Fe3C/Fe N/C) composites using an iron phenanthroline (Fe Phen) complex and dicyandiamide (DCA) as the precursors that are subsequently heat treated. The optimal catalyst pyrolyzed at 800 degC (Fe Phen N 800) exhibits superior oxygen reduction activity with onset and half wave potentials of 0.99 and 0.86 V in 0.1 M KOH, respectively, which are higher than those of Pt/C (onset and half wave potentials of 0.98 and 0.84 V) at the same catalyst loading. Moreover, the obtained Fe Phen N 800 displays comparable activity to Pt/C in 0.1 M HClO4 solution. Notably, the well developed Fe Phen N 800 catalyst shows much higher long term stability and better methanol tolerance than Pt/C. The results suggest that our catalyst is one of the most promising candidates to replace Pt catalysts toward oxygen reduction. Strikingly, a primary Zn air battery using Fe Phen N 800 as the air cathode catalyst delivers higher voltages and gravimetric energy densities than those of a Pt/C based system at the discharge current densities of 10 and 25 mA cm 2, thus demonstrating the potential applications of our catalyst for energy conversion devices.