Cobalt, Nitrogen-Doped Porous Carbon Nanosheet-Assembled Flowers from Metal-Coordinated Covalent Organic Polymers for Efficient Oxygen Reduction

The breakthrough of nonprecious metal catalysts replacing platinum-based catalysts toward the oxygen reduction reaction (ORR) is extremely urgent for the development of high-efficiency energy conversation systems. Herein, a solution-processed condensation polymerization using cyanuric chloride and piperazine as the monomers was proposed for the synthesis of a nitrogen-rich covalent organic polymer (COP). High contents of precisely tailored pyridinic-N within the COP facilitate the formation of the Co/N coordination between Co ions and N species. As a result, the subsequent carbonization of the Co-coordinated COP led to the formation of the cobalt, nitrogen dual-doped porous carbon nanosheet-assembled flowers (Co/N-PCNF). The as-obtained Co/N-PCNF catalyst with a nearly 4-electron oxygen reduction pathway exhibits an excellent ORR catalytic activity with a half-wave potential of 0.835 V comparable to the commercial Pt/C catalysts (0.865 V). Most impressively, the Co/N-PCNF catalyst displays a long-term stability and a much better resistance to methanol than the Pt/C catalyst because of its high surface area, well-defined porous structure, and homogeneous distributions of active sites within the carbon matrix. Therefore, this work establishes an operating rule for tailored synthesis of COP-derived nonprecious metal catalysts offering high activity for the ORR in electrochemical energy conversations.