Apically Co- nanoparticles- wrapped nitrogendoped carbon nanotubes from a single- source MOF for efficient oxygen reduction

Metal-organic framework (MOF)-derived transition metal/carbon nanotubes composites (TM/CNTs) have been developed as a promising oxygen electrocatalyst for energy conversion devices. However, relatively complicated synthesis limits current research to a handful of MOFs precursors. Herein, we used a single-source dicyanamide-based Co-MOF to prepare cobalt nanoparticles-wrapped bamboo-like nitrogen-doped carbon nanotubes (Co@BNCNTs) by a short-term (3 h) one-step pyrolysis at a lower temperature (as low as 700 degrees C). Organic dicyanamide linkers on the framework of Co-MOF not only served as the nitrogen source but also conduced to the formation of CNTs, and inorganic Co nanoparticles are enclosed in situ in graphitic carbon shells. Co@BNCNTs exhibited comparable oxygen reduction electrocatalytic activity and enhanced stability to commercial 20 wt% Pt/C catalyst in alkaline solution. Remarkably, rechargeable Zn-air batteries based on Co@BNCNTs as the air cathode demonstrated excellent cycling stability with no increase in polarization even after 65 h. The single-source MOF as precursor offers more facile and designable method for highly active and durable catalysts for various specific reactions.