Pyrolysis-Mediated Polycyano Strategy for Directed Construction of Fe₃C-Synergized Fe─N Carbon Nanotubes...

Precise modulation of the coordination environment of Fe─N_x sites is crucial yet challenging for enhancing the intrinsic activity of single-atom Fe/N-codoped carbon catalysts toward the oxygen reduction reaction (ORR). Herein, N-doped carbon nanotubes embedded with Fe₃C nanoparticles with abundant pyridinic-N and Fe─N_x active sites are prepared by simple pyrolysis of precursors containing Zn²⁺/Fe²⁺ and cyano groups. The optimized Fe₃C/FeN@CNT-900 catalyst exhibits a remarkable ORR half-wave potential (E_1/2) of 0.89 V versus RHE, along with exceptional methanol tolerance and SCN^- resistance. The power density of the zinc-air battery with this cathode achieves 1.65 times of that of the battery using the Pt/C+RuO₂ catalyst. Experimental and theoretical analyses reveal that these enhancements arise from tailored electronic structures and optimized intermediate adsorption at Fe active centers. Synergistic catalysis between atomic Fe─N_x sites and Fe₃C nanoparticles lowers the energy barrier of the ORR rate-determining step by facilitating interfacial electron transfer, as evidenced by density functional theory calculations. This work provides a rational strategy for designing high-performance dual-active sites in metal-nitrogen-carbon electrocatalysts and highlights the critical role of atomic-nanoparticle interactions in advanced energy conversion systems.