Crafting core–shell heterostructures of carbon nanotubes and N,O-coordinated cobalt site-impregnated conjugated porous polymers for highly efficient oxygen reduction

Abstract

The ability to develop high-efficiency carbon-based single-metal-atom catalysts (SMACs) via facile routes represents an important endeavor toward high-performance oxygen reduction reaction (ORR). Herein, we report a simple yet viable one-step pyrolysis-free approach via cobalt ion-mediated in situ Schiff-base condensation of π-conjugated monomers in the presence of highly conductive carbon nanotubes (CNTs) for crafting core–shell coaxially heterostructured CNTs/N,O-coordinated cobalt site-impregnated conjugated porous polymers (denoted as CNTs/Co–N,O-CPs) as a superior electrocatalyst for highly efficient ORR. Notably, the CNTs/Co–N,O-CPs possess an advantageous 1D heterostructure with abundant hierarchical porosity, thereby greatly favoring the efficient exposure of active sites and fast electron and mass transport. More importantly, theoretical calculations reveal that the strong orbital interaction between central Co and coordinated O atoms considerably optimizes the adsorption strengths of ORR-relevant intermediates, accounting for the markedly enhanced intrinsic activity of CNTs/Co–N,O-CPs. Consequently, the CNTs/Co–N,O-CPs manifest superior performance for the ORR (i.e., onset potential of 1.004 V and half-wave potential of 0.868 V) and zinc–air batteries (i.e., maximal power density of 181 mW cm⁻² and specific capacity of 814 mA h g_Zn⁻¹) in an alkaline medium, outperforming most previously reported carbon-based SMACs and even surpassing the state-of-the-art Pt/C catalyst. As such, the rationally crafted pyrolysis-free CNTs/Co–N,O-CPs may stand out as a robust ORR electrocatalyst for high-performance energy conversion devices.