Abstract: Developing efficient bifunctional oxygen catalysts is critical for advanced rechargeable zinc-air batteries (ZABs). Here, we report a substrate-free spatial separation pyrolytic deposition strategy to synthesize highly dispersed metal nanoparticles (iron (Fe), cobalt (Co), nickel (Ni), and their alloys) embedded in N-doped carbon matrices (M@NC). By spatially separating precursor decomposition and product deposition, this method achieves controlled growth of carbon nanotubes with uniformly distributed nanoparticles while preventing metal and carbon aggregation. Among mono-/bimetallic composites, FeNi@NC catalyst emerges as a superior bifunctional oxygen electrocatalyst, achieving a low potential gap (ΔE = 0.81 V) for oxygen reduction and evolution reactions in 0.1 mol·L^-1 KOH. The excellent bifunctionality is attributed to Fe-Ni alloy-induced electronic modulation and interfacial charge transfer between the alloy core and graphitic carbon shell. When integrated into ZABs, FeNi@NC catalyst demonstrates a peak power density of 234 mW·cm^-2 and exceptional cycling stability (>700 cycles), outperforming Pt/C + RuO₂. Systematic studies reveal that bimetallic synergy reduces nanoparticle size and enhances CNT growth, while excessive metal loading or ternary systems degrade performance. XPS analyses confirm the critical roles of pyridinic/graphitic N and M-N-C covalent bonds in stabilizing active sites. This work provides a scalable synthesis paradigm and mechanistic insights into composition-structure-activity relationships.

Key words: Electrochemistry, Nanoparticles, Transition metal/carbon, Interface, Reaction kinetics, Zinc-air batteries

摘要： Developing efficient bifunctional oxygen catalysts is critical for advanced rechargeable zinc-air batteries (ZABs). Here, we report a substrate-free spatial separation pyrolytic deposition strategy to synthesize highly dispersed metal nanoparticles (iron (Fe), cobalt (Co), nickel (Ni), and their alloys) embedded in N-doped carbon matrices (M@NC). By spatially separating precursor decomposition and product deposition, this method achieves controlled growth of carbon nanotubes with uniformly distributed nanoparticles while preventing metal and carbon aggregation. Among mono-/bimetallic composites, FeNi@NC catalyst emerges as a superior bifunctional oxygen electrocatalyst, achieving a low potential gap (ΔE = 0.81 V) for oxygen reduction and evolution reactions in 0.1 mol·L^-1 KOH. The excellent bifunctionality is attributed to Fe-Ni alloy-induced electronic modulation and interfacial charge transfer between the alloy core and graphitic carbon shell. When integrated into ZABs, FeNi@NC catalyst demonstrates a peak power density of 234 mW·cm^-2 and exceptional cycling stability (>700 cycles), outperforming Pt/C + RuO₂. Systematic studies reveal that bimetallic synergy reduces nanoparticle size and enhances CNT growth, while excessive metal loading or ternary systems degrade performance. XPS analyses confirm the critical roles of pyridinic/graphitic N and M-N-C covalent bonds in stabilizing active sites. This work provides a scalable synthesis paradigm and mechanistic insights into composition-structure-activity relationships.

关键词: Electrochemistry, Nanoparticles, Transition metal/carbon, Interface, Reaction kinetics, Zinc-air batteries