Bimetallic organic framework-derived rich pyridinic N-doped carbon nanotubes as oxygen catalysts for rechargeable Zn-air batteries

Abstract

Developing of low-cost and high-performance electrocatalysts provides a promising method to alleviate the burden of noble metals for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The oxygen catalysts play an increasingly greater role in expanding the energy conversion efficiencies of rechargeable Zn-air batteries. Metal organic frameworks (MOFs) have greatly noticed as versatile precursors to design and establish highly efficient bifunctional catalysts owing to their adjustable component, flexible tailing capability and high surface area. Herein, a highly active OER/ORR catalyst was synthesized by a facile metal induction pyrolysis strategy using bimetallic NiCo-ZIF-67 as precursor, obtaining a special characteristics with high pyridinic N doping level (~42.6%) and ultrafine metal nanocrystals embedded in carbon nanotubes. The as-prepared Ni1Co3@N-CNTs demonstrates a moderate OER activity with a low overpotential of only ~290 mV at 10 mA cm−2 and a low Tafel slop of 56 mV dec−1. Meanwhile, it reaches a much higher half-wave potential of 0.85 V for ORR, which could rival the most of reported materials. Importantly, when being applied as oxygen catalyst in rechargeable Zn-air batteries, decent electrochemical performance of open-circuit potential and high power density were achieved, even superior than those of the commercial Pt/C and RuO2 electrode.