Gas-phase synthesis of metal (M=Co, Cu, Mn, Ni, Fe) nanoparticles on N-doped carbon nanofibers as excellent oxygen electrocatalyst.

The particle size and dispersity of metal particles are key factors affecting the activity of electrocatalysts. Herein, employing N-doped carbon fiber as support, we report a facile gas-phase transport strategy for the synthesis of a series of transition metal nanoparticles (denoted as M/N-CF, M = Co, Cu, Mn, Ni, Fe). The current synthesis strategy not only yields metal nanoparticles with ultra-small size (∼5 nm) and good monodispersity, but also introduces a porous nanostructure with large surface area (730 m2 g−1) and rich M-N species. When used for catalyzing oxygen reduction reaction, all the M/N-CF catalysts adopt a highly efficient 4e− ORR pathway, reaching a most positive half-wave potential of 0.87 V vs. RHE for Mn/N-CF, quite approaching that of commercial Pt/C (0.88 V vs. RHE). Among them, Co/N-CF can also catalyze oxygen evolution reaction in an overpotential of 380 mV at 10 mA cm−2, approaching that of commercial RuO 2 (295 mV). Furthermore, as air electrode for rechargeable Zn-air battery, Co/N-CF based device achieves a high power density (163 mW cm−2) and good long-term cycling stability (over 50 h at 10 mA cm−2), suggesting the potential application of M/N-CF catalysts in energy conversion and storage systems. Image 1 • A facile and universal gas-phase transport strategy is presented to synthesize a series of transition metal based oxygen electrocatalysts (M/N-CF). • M/N-CF catalysts possess a porous nanostructure with large surface area and rich M − N species. • All the M/N-CF catalysts can catalyze ORR in a highly efficient 4e− ORR pathway. • Co/N-CF can simultaneously catalyze ORR and OER, achieving a high power density (163 mW cm−2) and good long-term cycling stability as air electrode in Zn-air battery. [ABSTRACT FROM AUTHOR]