Dichotomizing the Oxygen Electrocatalytic Properties of Doped Carbon Catalysts in Acid through a Salt-Activated Synthesis

Scalable Synthesis of Micromesoporous Iron-Nitrogen-Doped Carbon as Highly Active and Stable Oxygen Reduction Electrocatalyst

Micromesoporous metal-nitrogen-doped carbons have attracted incremental attention owning to their high activities for the electrocatalyzing oxygen reduction reaction (ORR). However, scalable synthesis of micromesoporous metal-nitrogen-doped carbons having superior electrocatalytic activity and stability remains a challenge. Here, an iron-nitrogen-doped carbon with highly electrocatalytic properties was simply prepared by ZnCl₂ activation of an in situ polymerized iron-containing polypyrrole (PPy@FeCl_x) at high temperature. High yields of polypyrrole (∼98 wt %) and iron-nitrogen-doped carbon (∼47 wt %) could be reached. The eutectic state of FeCl_x-ZnCl₂ and its derived ZnFe₂O₄ maskant played important roles in making micromesopores, scattering iron atoms, and trapping nitrogen atoms, leading to numerous micromesopore defects, a larger specific surface area, a more nitrogen doping content, and active sites for the material. The electrochemical tests and Zn-air battery measurements showed that the micromesoporous iron-nitrogen-doped carbon could achieve much positive onset and half-wave potentials at 0.98 and 0.90 V, respectively, as well as a large current density (6.06 mA/cm²) and good cycling stability. The combination of the iron-nitrogen doping and micromesopore defects by the eutectic salt activation method provided an effective way to scalable synthesize iron-nitrogen-doped carbon as highly active and stable oxygen reduction electrocatalytsts.