Dual active sites of the Co₂N and single-atom Co–N₄ embedded in nitrogen-rich nanocarbons: a robust electrocatalyst for oxygen reduction reactions

The development of low-cost, highly efficient and durable non-precious-metal (NPM) electrocatalysts for the oxygen reduction reaction (ORR) is of great significance. Herein, we report an ingenious two-step strategy for the fabrication of NPM electrocatalysts containing multifarious cobalt species embedded in nitrogen-rich nanocarbons (Co–N–C). Firstly, Co ions were fixed by coordination with 1H-Imidazo[4,5-f][1,10]phenanthroline (Hip), and secondly the Co–Hip precursor with abundant Co, C and N sources was subjected to calcination at various temperatures (700–900 °C). The obtained Co–N–C catalysts exhibited excellent activity in terms of the ORR in alkaline conditions, with a half-wave potential of 0.82 eV versus the reversible hydrogen electrode, which is close to that of commercial Pt/C. Moreover, the Co–N–C exhibited an unexpected catalytic activity with long-term stability and immunity to methanol which is better than commercial Pt/C catalyst, suggesting that Co–N–C with dual active sites of the single-atom Co sites (Co–N₄) and Co₂N can be a promising alternative to replace Pt-based electrocatalysts in fuel cells. This work can provide a new route to designing promising catalysts with dual active sites for ORR. (paper)