Ferrocene-crosslinked polypyrrole hydrogel derived Fe-N-doped hierarchical porous carbon as an efficient electrocatalyst for pH universal ORR and Zn-air batteries

Herein, a cost-effective and high-efficiency Fe-N-doped carbon-based catalyst, denoted as PF-800, was facilely prepared via direct carbonization of a polypyrrole hydrogel (PF) using low cost and commercially mass-produced ferrocenedicarboxylic acid as the cross-linking agent and dopant, simultaneously. Combining the features of hierarchical pore structure and Fe-N-doped elemental composition, PF-800 displays impressive activity for the oxygen reduction reaction (ORR) in the whole pH range. Further application in practical devices validates that Zn-air batteries using PF-800 as the cathode catalyst present high power and energy density as well as excellent long-term running stability, outperforming the batteries equipped with commercial Pt/C (20%). This study paves a way for the rational design of low-cost Fe-N-C catalysts for renewable energy applications.