Heat-treated 2,2′-bipyridine iron complex supported on polypyrrole-coated carbon for oxygen reduction reaction

Nitrogen-containing non-noble metal catalysts for oxygen reduction reaction (ORR) are prepared by supporting 2,2′-bipyridine iron complex on polypyrrole-coated carbon support followed by pyrolysis at various temperatures (600, 700, 850, and 1000 °C). The prepared catalysts and support are characterized by IR, elementary analysis, TEM, and XPS. Revealed is that the contents of pyridinic nitrogen on a catalyst would not be a determining factor for ORR activity. The concentration of pyridinic nitrogen diminishes with the increasing pyrolysis temperature, while the ORR performance is observed to be enhanced with a maximum at 850 °C. It is believed that the pyridinic nitrogen added as a precursor should be activated to serve as an active site for ORR, indicating that an increasing pyrolysis temperature is favored to form a highly active site. However, the pyrolysis at too high of temperature (1000 °C) turns out to be undesirable due to a considerable loss of active nitrogen.