Pyrolysis of Iron‐Containing Polyanilines under Micropore Generation Control: Electrocatalytic Performance in the Oxygen Reduction Reaction

Pyrolyzed iron‐containing polyaniline (C−Fe‐PANI) is one of the most promising candidates as a non‐precious metal based electrocatalyst for oxygen reduction reaction (ORR). Although the ORR activity depends on the surface area arisen from pyrolysis‐generated micropores on C−Fe‐PANI particles, the micropore generation is hindered by pyrolysis‐formed iron nanoparticles (Fe NPs) embedded inside C−Fe‐PANI particles. Here, we demonstrate the pyrolysis of iron‐containing PANIs under suppression of micropore‐generation hindrance by blocking the Fe NPs formation. The higher‐molecular‐weight (MW: 100,000) PANI was dispersed in an FeCl 3 solution before pyrolysis for preventing FeCl 3 penetration inside PANI particles. As a result, as compared to the case of lower‐MW (5,000) PANI, the Fe NPs formation was more suppressed inside catalyst particles to give 1.9 (1.8) times micropore volume (specific surface area), leading to a 11 % higher current density in ORR electrocatalytic performance test in acidic media.