Co-Zn-MOFs Derived N-Doped Carbon Nanotubes with Crystalline Co Nanoparticles Embedded as Effective Oxygen Electrocatalysts.

The oxygen reduction reaction (ORR) is a crucial step in fuel cells and metal-air batteries. It is necessary to expand the range of efficient non-precious ORR electrocatalysts on account of the low abundance and high cost of Pt/C catalysts. Herein, we synthesized crystalline cobalt-embedded N-doped carbon nanotubes (Co@CNTs-T) via facile carbonization of Co/Zn metal-organic frameworks (MOFs) with dicyandiamide at different temperatures (t = 600, 700, 800, 900 °C). Co@CNTs- 800 possessed excellent ORR activities in alkaline electrolytes with a half wave potential of 0.846 V vs. RHE (Reversible Hydrogen Electrode), which was comparable to Pt/C. This three-dimensional network, formed by Co@CNTs-T, facilitated electron migration and ion diffusion during the ORR process. The carbon shell surrounding the Co nanoparticles resulted in Co@CNTs-800 being stable as an electrocatalyst. This work provides a new strategy to design efficient and low-cost oxygen catalysts.