A metal–organic framework route to in situ encapsulation of Co@Co3O4@C core@bishell nanoparticles into a highly ordered porous carbon matrix for oxygen reduction

Abstract

Rational design of non-noble metal catalysts with an electrocatalytic activity comparable or even superior to Pt is extremely important for future fuel cell-based renewable energy devices. Herein, we demonstrate a new concept that a metal–organic framework (MOF) can be used as a novel precursor to in situ encapsulate Co@Co₃O₄@C core@bishell nanoparticles (NPs) into a highly ordered porous carbon matrix (CM) (denoted as Co@Co₃O₄@C–CM). The central cobalt ions from the MOF are used as a metal source to produce Co metal cores, which are later transformed into a fancy Co@Co₃O₄ nanostructure via a controlled oxidation. The most notable feature of our Co@Co₃O₄@C–CM is that the highly ordered CM can provide much better transport pathways than the disordered pure MOF derived nanostructure that can facilitate the mass transport of O₂ and an electrolyte. As a result, the well-designed Co@Co₃O₄@C–CM derived from the MOF shows almost identical activity but superior stability and methanol tolerance for the ORR relative to the commercial Pt/C in alkaline medium. Our work reports a novel Co@Co₃O₄@C nanostructure from a MOF for the first time and also reveals the important role of the introduction of a highly ordered carbon matrix into the MOF derived catalyst in enhancing the ORR activity and stability. To the best of our knowledge, the Co@Co₃O₄@C–CM is the most efficient non-noble metal nanocatalyst ever reported for the ORR.