Water-regulated and bioinspired one-step pyrolysis of iron-cobalt nanoparticles-capped carbon nanotubes/porous honeycombed nitrogen-doped carbon composite for highly efficient oxygen reduction

To achieve commercial applications of green fuel cells and rechargeable metal-air batteries, rational design and synthesis of low-cost, high-efficiency and ultra-stable transition metal-based electrocatalysts are of significant importance for alkaline oxygen reduction reaction (ORR). In this work, iron-cobalt (FeCo) nanoparticles-capped carbon nano-tubes/-porous nitrogen-doped honeycombed carbon composite (FeCo-CNTs/NHC-800) is synthesized by a water-regulated and bioinspired one-step pyrolysis method at 800 °C, where l-histidine behaves as the C and N sources combined by working as a chelating agent of Fe/Co. The formation mechanism is discussed by adjusting the pyrolysis temperature and water amount. The resultant FeCo-CNTs/NHC-800 exhibits a positive onset potential (Eonset = 1.091 V) and half-wave potential (E1/2 = 0.88 V), showing promising ORR activity, outperforming home-made controls and many lately reported catalysts. The hierarchically porous honeycombed structures have fascinating open porous spaces for fast diffusion of active species, large specific surface area, high conductivity, and stable sites for anchoring FeCo nanoparticles (NPs). Moreover, the N-doped carbon nanotubes coupling with homogeneous FeCo NPs greatly improve the catalytic activity and stability of ORR. This work provides some valuable insights to prepare hierarchical, reliable, and high-efficiency carbon-based ORR catalysts for new energy-correlated devices.