Bimetallic 3D hollow-nanoshell FeCo-oxynitride/N and S co-doped carbon nanotubes as a robust bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Herein, a novel 3D hierarchically hollow-shell porous structure of iron cobalt oxynitride anchored nitrogen and sulfur-doped bamboo-like carbon nanotubes (FeCo 2 ON/NSCNTs) are fabricated using a pyrolysis of Fe doped-ZIF-8/67@S-doped g-C 3 N 4 . The strong synergistic effects between hollow FeCo 2 ON, NC nanoshells, and NSCNTs lead to accelerating the mass and electron transfer between the active sites which is favorable for electrochemical activities. The introduction of Fe into the nanohybrid and nitrogen/sulfur atoms doped on CNTs leading to increase electrical conductivity and decrease the activation energy barrier of the rate-determining step. The electrocatalyst exhibit a more half-wave potential of 0.903 V vs. RHE, outperform to Pt/C. Moreover, the low overpotential of 268 mV at 10 mA cm −1 is attained for FeCo 2 ON/NSCNTs. Its superiority as the air-electrode electrocatalyst corroborates in a Zn–air battery with a higher power density and specific capacity (235.4 mW cm −2 , and 781 mAh g −1 , respectively) than Pt/C + RuO 2 (184.6 mW cm −2 , and 701 mAh g −1 ). Graphical abstract