Bimetallic covalent organic frameworks for constructing multifunctional electrocatalyst.

Covalent organic frameworks (COFs) are a new class of crystalline porous polymers, which comprise mainly of carbons and are versatile for integrating heteroatoms such as B, O and N to the skeletons. The designable structure and abundant composition render COFs useful as precursors for heteroatom-doped porous carbons for energy storage and conversion. Herein, we describe a multifunctional electrochemical catalyst by pyrolysis of a bimetallic COF. The catalyst possesses hierarchical pores and abundant iron and cobalt nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibited excellent electrochemical catalytic activity in oxygen reduction reaction (ORR), with a 50 mV positive half-wave potential, a higher limited diffusion current density, and a much smaller Tafel slope than Pt-C catalyst. Moreover, the catalyst displayed superior electrochemical performance towards hydrogen evolution reaction (HER) with over potentials of -0.26 V and -0.33 V in acidic and alkaline aqueous solution at a current density of 10 mA cm-2, respectively. And the overpotential in catalyzing oxygen evolution reaction (OER) was 1.59 V at the same current density.