Non-noble bimetallic alloy encased in nitrogen-doped nanotubes as a highly active and durable electrocatalyst for oxygen reduction reaction

Exploring highly active, cost-effective and durable oxygen reduction reaction (ORR) electrocatalysts as substitutes for the rare platinum-based catalysts is of great significance in energy conversion and storage devices, such as alkaline fuel cells, metal-air batteries, etc. Herein, we fabricated a new type ORR electrocatalyst of NiCo nanocrystal alloy encapsulated in N-doped carbon nanotubes (NCNTs) through a facile, scalable route utilizing nickel acetate and cobalt chloride as metallic Ni and Co precursors, thiourea as a nitrogen and carbon source, respectively, under a Ni/Co atomic ratio of 3:7 at 700 °C. The obtained nanocomposite catalyst NiCo@NCNT-700 exhibited an outstanding ORR activity close to that of the state-of-the-art Pt/C catalyst and superior operational durability under alkaline conditions, which could be attributed to the co-contributions among the uniformly distributed NiCo alloy nanoparticles, graphitic NCNTs and the formation of CoN species. This work provides a new insight for the rational design and development of efficient non-noble metal electrocatalysts by integrating electrochemically active units into the nanocomposite for challenging electrochemical energy-related technologies.

A new type of noble metal-free ORR electrocatalyst of NiCo nanocrystal alloy encapsulated in N-doped carbon nanotubes (NiCo@NCNT-700) is fabricated through a facile pyrolysis route. The NiCo@NCNT-700 demonstrates outstanding ORR activity highly comparable to the commercial Pt/C and excellent operational durability, markedly better than commercial Pt/C under alkaline conditions.195