Facile Synthesis of 3D Fe/N Codoped Mesoporous Graphene as Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

Exploring the oxygen electrocatalysts with both high oxygen reduction reaction (ORB.) and oxygen evolution reaction (OER) performance is crucial to developing the rechargeable Zn-air batteries (ZABs). Herein, we prepared a bifunctional three-dimensional graphene-like iron-nitrogen doped oxygen electrocatalyst (3D Fe/N-G#4, polyacrylamide (PAM):-NaCl = 1:4, mass ratio) by a facile synthesis with PAM and iron as precursors and NaCl as template. The NaCl template melted during the pyrolysis process, which could fabricate a stable 3D network structure in the precursors to form more mesopores, higher specific surface area, and more exposed active sites and prevent the loss of precursors. The low-cost and water-soluble PAM as the N precursor provided abundant N and dissolved adequately with NaCl solution. The Fe precursor coordinated with the N to form Fe-N-x active sites that were investigated by HR-TEM, XRD, XPS, and RDE techniques. The 3D Fe/N-G#4 exhibited excellent electrochemical activity with a high half-wave potential (0.852 V vs RHE) for ORR and a low overpotential (393 mV at 10 mA cm(-2)) for OER in the alkaline conditions. In addition, the homemade rechargeable ZAB based on the prepared 3D Fe/N-G#4 exhibits high power density (168.2 mW cm(-2)) and excellent discharge-charge cycling stability (over 60 h) at 20 mA cm(-2). This work provides a cost-efficient, simple, and eco-friendly method to synthesize excellent bifunctional non noble electrocatalysts for commercialization of ZABs.