Tailoring hierarchically porous nanoarchitectured N-doped carbon decorated with FeIIN4 moiety and encapsulated Fe/Fe3C nanoparticles as a synergistic catalyst for ORR in Zn-air battery

Rational designing and exploiting non-noble metal electrocatalysts with desirable nanoarchitecture and abun-dant active sites are crucial but challenging requirements for the development of fuel cells and Zn-air batteries (ZABs). Herein, a highly efficient carbonous hybrid is developed using a facile and effective synthesis strategy via template-assisted and optimized post-pyrolysis processes. The optimized electrocatalyst (denoted as Fe@NC-700) has extremely large specific surface area (1262.8 m2 g-1), and presents a desirable hierarchically porous nano -architecture, including plenty micro-/meso-pores, which endows the catalyst with the enhanced mass transfer for the reaction species. More importantly, Fe@NC-700 possesses not only numerous FeIIN4 moiety uniformly dispersed in N-doped carbon matrix, but also encapsulated Fe/Fe3C nanoparticles, synergistically boosting the electrocatalytic activity towards oxygen reduction reaction (ORR) verified by density functional theory (DFT) calculation. Due to the beneficial microstructure and rich active sites, the catalyst has a positive half-wave po-tential (E1/2) of 0.865 V for ORR in alkaline electrolyte, intrinsic 4e- reaction path and robust stability (only 14 mV negative shift of E1/2 after 10,000 potential cycles), outperforming the Pt/C. Impressively, the aqueous and quasi-solid-state primary ZABs assembled with Fe@NC-700 as cathode catalyst demonstrate superior discharge performance and excellent durability, holding promising potential in practical application of energy conversion devices.