The design of Fe, N-doped hierarchically porous carbons as highly active and durable electrocatalysts for a Zn-air battery.

A new type of Fe, N-doped hierarchically porous carbons (N-Fe-HPCs) has been synthesized via a cost-effective synthetic route, derived from nitrogen-enriched polyquaternium networks by combining a simple silicate templated two-step graphitization of the impregnated carbon. The as-prepared N-Fe-HPCs present a high catalytic activity for the oxygen reduction reaction (ORR) with onset and half-wave potentials of 0.99 and 0.86 V in 0.1 M KOH, respectively, which are superior to commercially available Pt/C catalyst (half-wave potential 0.86 V vs. RHE). Surprisingly, the diffusion-limited current density of N-S-HPCs approaches ∼7.5 mA cm(-2), much higher than that of Pt/C (∼5.5 mA cm(-2)). As a cathode electrode material used in Zn-air batteries, the unique configuration of the N-Fe-HPCs delivers a high discharge peak power density reaching up to 540 mW cm(-2) with a current density of 319 mA cm(-2) at 1.0 V of cell voltage and an energy density >800 Wh kg(-1). Additionally, outstanding ORR durability of the N-Fe-HPCs is demonstrated, as evaluated by the transient cell-voltage behavior of the Zn-air battery retaining an open circuit voltage of 1.48 V over 10 hours with a discharge current density of 100 mA cm(-2).