Bifunctional ligand Co metal-organic framework derived heterostructured Co-based nanocomposites as oxygen electrocatalysts toward rechargeable zinc-air batteries.

A heterostructured Co-based electrocatalyst is successfully synthesized using bifunctional ligand Co metal–organic frameworks as precursors. The bifunctional ligands provide enough N and O atoms that can simultaneously convert Co ions into CoN x moieties, Co nanoparticles and Co oxides via one-step pyrolysis. The obtained electrocatalysts with heterostructured CoO x /Co nanoparticles encapsulated by porous conductive carbon rich in CoN x active sites deliver remarkable oxygen reduction reaction and oxygen evolution reaction activities. With the synergistic effects among these multifunctional components, a rechargeable zinc–air battery built with this electrocatalyst exhibits a high-power density and long-lasting rechargeability. [Display omitted] Rational construction of efficient and robust bifunctional oxygen electrocatalysts is key but challenging for the widespread application of rechargeable zinc-air batteries (ZABs). Herein, bifunctional ligand Co metal–organic frameworks were first explored to fabricate a hybrid of heterostructured CoO x /Co nanoparticles anchored on a carbon substrate rich in CoN x sites (CoO x /Co@Co N C) via a one-step pyrolysis method. Such a unique heterostructure provides abundant CoN x and CoO x /Co active sites to drive oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. Besides, their positive synergies facilitate electron transfer and optimize charge/mass transportation. Consequently, the obtained CoO x /Co@Co N C exhibits a superior ORR activity with a higher half-wave potential of 0.88 V than Pt/C (0.83 V vs. RHE), and a comparable OER performance with an overpotential of 346 mV at 10 mA cm−2 to the commercial RuO 2. The assembled ZAB using CoO x /Co@Co N C as a cathode catalyst displays a maximum power density of 168.4 mW cm−2, and excellent charge–discharge cyclability over 250 h at 5 mA cm−2. This work highlights the great potential of heterostructures in oxygen electrocatalysis and provides a new pathway for designing efficient bifunctional oxygen catalysts toward rechargeable ZABs. [ABSTRACT FROM AUTHOR]