Heteroatom-Doped Carbon Electrocatalysts Derived from Nanoporous Two-Dimensional Covalent Organic Frameworks for Oxygen Reduction and Hydrogen Evolution

Electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are vital in the renewable energy platform, particularly fuel cells and rechargeable batteries, where construction of efficient electrocatalysts is a crucial task. In contrast to noble-metal catalysts, heteroatom-doped carbons have recently emerged as new-generation electrocatalysts because of their low cost and high stability/activity. Although unique features of covalent organic frameworks (COFs) including high surface areas, adjustable apertures, and easy introduction of diverse heteroatoms render them promising precursors for heteroatom-doped carbons, development of electrocatalysts derived from COFs with simultaneously high activities of ORR/HER is still at an early stage. Here, we report the creation of metal-free heteroatom-doped carbon catalysts derived from four types of newly designed nanoporous two-dimensional COFs with ordered pores smaller than 1 nm. Both preincorporated N in the pristine COFs and postdoped P heteroatoms are uniformly distributed into the graphitized carbons and functioning as effective active sites for electrocatalysis. Furthermore, the obtained heteroatom (N, P) codoped carbons possess nanoporosity beneficial for efficient introduction of reactants. Therefore, the N, P codoped nanoporous carbons demonstrate robust electrochemical performances for both ORR and HER with a half-wave potential of 0.81 V in alkaline medium and low overpotential of 260 mV in acid solutions. In addition, their catalytic activities are not changed after a long-time cycle. These findings will promote creation of robust COF-derived carbon catalysts in energy storage and conversion as well as development of new COFs with tunable nanopores.