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Tailoring N-Coordination Environment by Ligand Competitive Thermolysis Strategy for Efficient Oxygen Reduction.

The synergy of fully-exposed active sites and optimized N-dopant configurations in three-dimensional (3D) N-doped carbon (N/C) is highly pivotal for efficient catalysis and energy conversion but lacks effective methods. Meanwhile, to understand the active sites, excluding the size effect of the π-conjugated system, especially in N/C derived from metal-organic-frames (MOFs), is significant but challenging. Herein, an elegant and general strategy, ligand competitive thermolysis, was developed to construct hierarchical-pore structures and tailor their N-coordination environment in the MOF-derived, 3D N/C catalysts. Due to sufficient interior mesopores and predominant active-N species, the metal-free catalysts achieved efficient activity (E1/2 = 0.84 V) and impressive durability (20,000 cycles, E1/2 = 5 mV). The relationship between half-wave potential and the content of N species were also investigated. This work not only offers valuable inspiration for developing high-performance electrocatalysts, but also motivates deep understanding of the active sites in N/C catalysts.