Developing nitrogen and Co/Fe/Ni multi-doped carbon nanotubes as high-performance bifunctional catalyst for rechargeable zinc-air battery.

[Display omitted] • A strategy is developed to obtain CoFeNi/ N -doped carbon nanotubes CoFeNi@CNT. • CoFeNi@CNT consists of Co/Fe/Ni N C and CoFeNi nanoparticles active sites. • It shows oxygen bifunctional catalytic activities with an overpotential of 850 mV. • The CoFeNi@CNT electrode shows high power density and durability in Zn-air battery. • The catalyst is low cost with tunable components and lenient reaction conditions. Rational construction of advanced bifunctional catalysts with dual-active-sites is still challenging for both oxygen reduction (ORR) and oxygen evolution reactions (OER). Herein, metal-doped dicyandiamide formaldehyde resin is innovatively exploited to synthesize N/Co/Fe/Ni multi-doped carbon nanotubes (denoted as CoFeNi@CNT) with metal-nitrogen-carbon (M N C) and CoFeNi nanoparticles as the ORR and OER active sites, respectively. Abundant active sites and high degree of graphitization enable CoFeNi@CNT with a high ORR half-wave potential of 0.82 V and a low OER overpotential of 440 mV at 10 mA cm−2, which are comparable or superior to noble-metal catalysts. Particularly, the CoFeNi@CNT air electrode of rechargeable Zn-air batteries shows remarkable open circuit potential (1.46 V), discharge power density (152.3 mW cm−2), specific capacity (814 mAh g−1), and cycling stability for more than 250 h. It is worth emphasizing that this synthesis strategy is rather simple, low-cost, high yield, and the proportion and amount of doped metal ions can be easily adjusted according to the needs for different applications. [ABSTRACT FROM AUTHOR]