Solvent effect to modulate nitrogen dopant in Co-N-C catalysts for oxygen reduction reaction acceleration.

[Display omitted] • The content of pyridinic N in Co-N-C catalysts is modulated via solvent effect. • DFT calculations reveal that the synergy of pyridinic-N and CoN x significantly accelerate the ORR. • The content of pyridine N in the prepared atomically dispersed Co-N-C catalyst is up to 43.7%. • The optimal Co-N-C catalyst exhibits high ORR activity in acid media. Rational design of platinum group metal (PGM)-free catalysts, e.g., M−N−C catalysts, with well-defined structure is highly essential to replace the conventional PGM-based catalysts towards oxygen reduction reaction (ORR), which, however, is still challenging. Particularly, extra nitrogen plays an important role in the ORR performance of M−N−C but the mechanism remains unclear. In this work, a facile modulation strategy based on solvent effect is proposed to tailor nitrogen dopants in the metal organic frameworks (MOFs)-derived Co-N-C catalysts. DFT calculations reveal that the synergy of pyridinic-N and CoN x significantly accelerate the ORR. Reasonably, the optimized Co-N-C catalyst shows superior onset potential (E onset) of 0.915 V and half-wave potential (E 1/2) of 0.785 V toward ORR. This work may pave an avenue for the precise construction of active moieties in large-scale preparation of PGM-free ORR catalyst. [ABSTRACT FROM AUTHOR]