Cobalt nanoparticles incorporated into hollow doped porous carbon capsules as a highly efficient oxygen reduction electrocatalyst

Abstract

Platinum-based materials have been the dominant and best electrocatalysts for promoting the oxygen reduction reaction (ORR). However, going beyond state-of-the-art catalysts remains a great challenge. Recently, nanostructured composites of conductive carbons and earth-abundant metals have emerged as promising electrocatalysts. Herein, we report a facile and practical approach for the synthesis of cobalt nanoparticles embedded into hollow nitrogen/cobalt-doped porous carbon capsules (Co@NPCC). The fabrication of this material was achieved via the thermal decomposition of sacrificial metal-organic framework nanocrystals coated with a metal-tannic acid coordination polymer shell, upon pyrolysis, which delivers zerovalent cobalt nanoparticles embedded in the walls of hollow capsules. Co@NPCC proved to be a superb catalyst for the electrochemical ORR, showing a highly positive onset potential (∼1.02 V vs. RHE) and current density (∼5.2 mA cm-2) in 0.1 M KOH electrolyte. These values are in excellent agreement with those reported for the state-of-the-art Pt/C catalyst. Significantly, materials produced via this approach can be manufactured on a large scale, thereby providing access to next-generation catalysts for important electrochemical processes.