Confining Iron Carbide Nanocrystals inside CNx@CNT toward an Efficient Electrocatalyst for Oxygen Reduction Reaction.

The development of low-cost electrocatalysts with comparable activity for oxygen reduction reaction (ORR) to substitute platinum-based catalysts is imperative but still challenging for the commercialization of fuel cells. Herein, we reported a strategy to effectively confine iron carbide nanocrystals in N-doped carbon coated on carbon nanotubes (CNx@CNT), which prevented the agglomeration of iron carbide during pyrolysis and thus provided the sufficient highly active catalytic sites. Together with the benefit from three-dimensional conductive network of CNT-based core-shell structure for fast electron transfer and rapid mass transfer, the developed nanocatalyst exhibited the significantly enhanced electrocatalytic activity for ORR, as well as high durability and methanol tolerance. Moreover, it was interestingly found that the types of the confined iron compounds appreciably affected the performance of the catalysts, and Fe3C might be most effective on improving ORR activity in this case.