Bimetallic Mn and Co encased within bamboo-like N-doped carbon nanotubes as efficient oxygen reduction reaction...

The development of oxygen reaction reduction (ORR) electrocatalysts that are low-cost, highly-active and have long-term stability for use in energy conversion and storage applications such as fuel cells and metal-air batteries is very important. In this paper, a facile one-step pyrolysis method was used to prepare bamboo-like N-doped carbon nanotubes (BNCNTs) as effective ORR electrocatalysts. Manganese and cobalt salts were used as the metal precursors, and urea was the C and N source. The resulting catalysts were characterized by the scanning electron microscopy, high resolution-transmission electron microscopy, X-ray photoelectron spectroscopy, Raman microscopy and X-ray power diffraction. The BNCNTs contained Mn and Co nanoparticles that were coated with graphitic carbon. The electrochemical performances of the catalysts in alkaline media were evaluated using cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The BNCNTs prepared with a Mn to Co molar ratio of 1:1 at 800 °C had the best catalytic activity. The reaction followed a quasi-4 electron reaction pathway with a smaller Tafel slope (57.5 mV dec^-1) than that of the commercial Pt/C (72.8 mV dec^-1). In addition, the limiting current density, durability and methanol crossover resistance were all superior to those of Pt/C. The above results indicate that Mn/Co-BNCNTs-800 is an active electrocatalyst with earth-abundant non-precious elements for ORR.