Ni/Fe Clusters and Nanoparticles Confined by Covalent Organic Framework Derived Carbon as Highly Active Catalysts toward Oxygen Reduction Reaction and Oxygen Evolution Reaction

Developing bifunctional electrocatalysts with high activity toward the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of great significance for metal-air batteries. Herein, a covalent organic framework (COF)-derived bifunctional electrocatalyst toward the ORR and the OER is demonstrated, in which the COF-derived carbon on carbon nanotubes is used as the support to anchor active bimetal Ni/Fe clusters and nanoparticles. Since Ni/Fe ions are immobilized in the pore channels of the COFs, the aggregation and migration of ions under pyrolysis are effectively hindered. In addition, the COF-derived carbon-made catalyst features abundant nitrogen content and a high mesoporous volume. As a result, the catalyst displays ultrahigh ORR activity, with a half-wave potential of 0.87 V versus reversible hydrogen electrode in 0.1 m KOH electrolyte. Moreover, the catalyst achieves a low operating potential of 1.55 V at a current density of 10 mA cm(-2), with a Tafel slop of 61 mV decade(-1) for OER in 0.1 m KOH, superior to most oxygen electrocatalysts. Furthermore, the catalyst also exhibits remarkable performance in Zn-air batteries. This work demonstrates a new insight into developing bifunctional catalysts from COFs.