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It is an urgent and difficult task to develop low-cost, high-performance catalysts for the oxygen reduction reaction (ORR) to overcome the inherent defects of platinum-based catalysts, including low abundance, high cost, poor stability, and poor methanol tolerance. In this study, N-doped carbon nanotubes (N-CNTs) and Co/N-CNT catalysts are synthesized by grinding and subsequent calcination, and the whole process does not require strict control of the reaction conditions, thus greatly simplifying the synthesis route of the catalysts. The unique structure, in which Co nanoparticles are evenly embedded in the tube and tip of CNTs, exhibits outstanding ORR performance and electrochemical stability as a result of the Co–CNT interactions. Furthermore, due to the catalytic graphitization ability of Co nanoparticles, a high graphitization degree, large specific surface area, and abundant pore structure are achieved by adjusting the calcination temperature, thus accelerating electron transfer and oxygen diffusion. The optimized catalyst, calcined at 750 °C (Co/N-CNT-750), exhibits better ORR activity and excellent methanol tolerance in alkaline media, indicating its great potential for large-scale application in storage technologies.

It is of significant implication to fabricate high-performance, durable and low-cost catalysts toward to oxygen reduction reaction (ORR) to drive commercial application of fuel cells. In our work, we synthesize the Fe/N-CNT catalyst via one-pot grinding combined with calcination using a mixture of carbamide, CNTs and iron salts as precursors, the as-synthesized catalysts show the structure that Fe nanoparticles are encapsulated in the tube of intertwined CNTs with abundant active sites. The catalyst is synthesized at 800 °C (Fe/N-CNT-800–20) obtain high graphitization degree and high N doped content, especially the high content and proportion of Fe–N and pyridinic-N, exhibiting outstanding ORR activity. Moreover, too high calcination temperature (850 °C) and high Fe content (25%) lead to the agglomeration of Fe during the calcination, which blocked some catalytic sites, leading to poor ORR activity. This facile synergy route will provide new thoughts for the fabrication and optimization of catalysts.