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Employing P-doped polypyrrole nanotubes as precursor, we have constructed a structure of N, P-codoped carbon nanotubes coupled with Co 2 P nanoparticles (Co 2 P/NPC). Herein, P element serves as a bridging agent enabling strong electronic coupling between NPC and Co 2 P. While Co 2 P with good electrical conductivity facilitates electron transfer during electrocatalytic process. As a result, Co 2 P/NPC can catalyze oxygen reduction reaction (ORR) in a direct 4e− pathway, reaching a half-wave potential of 0.835 V vs. RHE and a smaller Tafel slope of 45.9 mV dec−1 than commercially available Pt/C. On the other hand, Co 2 P/NPC can also catalyze oxygen evolution reaction (OER) in a low overpotential of 320 mV at 10 mA cm−2 and a smaller Tafel slope of 59.6 mV dec−1 than commercially available RuO 2. Finally, the potential application of Co 2 P/NPC catalyst is estimated in case of rechargeable Zn-air battery. As air electrode, Co 2 P/NPC achieves a power density of 154 mW cm−2 and good long-term cycling stability (over 90 h at 5 mA cm−2). Our work thus provides a facile strategy to achieve bifunctional ORR/OER performance for application in next-generation energy conversion systems. • N, P-codoped carbon nanotubes coupled with Co 2 P nanoparticles is constructed. • Co 2 P/NPC exhibits strong electronic coupling between NPC and Co 2 P. • Co 2 P/NPC can catalyze ORR and OER with good activity and stability. • Co 2 P/NPC demonstrates potential application in rechargeable Zn-air battery. [ABSTRACT FROM AUTHOR]

The development of highly efficient and bifunctional electrocatalysts is highly desirable for commercializing the rechargeable Zn-air battery. Herein, employing graphitic carbon nitride as carbon precursor, N-doped carbon sheets loaded with Ni 3 Fe nanoparticles (denoted as Ni 3 Fe/N-C) have been prepared via a simple pyrolysis strategy. Benefitting from the introduction of triethylene diamine as organic ligand, Ni 3 Fe nanoparticles with a mean size of 29 nm are dispersed on N C sheets uniformly. As a result, Ni 3 Fe/N-C exhibits excellent electrocatalytic activity toward both oxygen reduction and evolution reactions (For oxygen reduction reaction, the half-wave potential of Ni 3 Fe/N-C is 0.81 V; for oxygen evolution reaction, the overpotential at 10 mA cm−2 is 310 mV). Finally, when used as air electrode in rechargeable Zn-air battery, a high power density of 128 mW cm−2 and a long cycling life up to 134 h at 10 mA cm−2 are achieved. Our study thus provides a promising air electrode material for rechargeable Zn-air batteries. [ABSTRACT FROM AUTHOR]