Analysis of forming process of nitrogen-doped carbon catalyst derived from Fe 1,10-phenanthroline compound and its oxygen reduction reaction activity

•1,10-phenanthroline was used as a nitrogen-doped carbon catalyst precursor.•Pyrolysis behavior of iron 1,10-phenanthroline compound was investigated. > Drastic mass loss was observed above 650 °C.•Iron carbide (Fe3C) was formed at 700 °C.•ORR activity of nitrogen-doped carbon catalyst was drastically improved between 600 and 700 °C.•The pyridine-like nitrogen to quaternary nitrogen ratio might affect the improvement of ORR activity.

The pyrolysis behavior of iron 1,10-phenanthroline compound, the change of crystalline structure of iron in the iron 1,10-phenanthroline compound, and nitrogen chemical state of nitrogen doped carbon catalyst derived from iron 1,10-phenanthroline compound were investigated to clarify the process of improvement of oxygen reduction reaction (ORR) activity on nitrogen-doped carbon catalyst by TGA, EGA-MS, HT-XRD, XRD, and XPS technique. The ORR activity drastically improved at a synthesis temperature of 700 °C, and was the highest at a synthesis temperature of 800 °C. But the ORR activity significantly dropped at a synthesis temperature of 900 °C. This low ORR activity of NC-900 is probably due to the increase of quaternary nitrogen ratio with progression of excessive carbonization, and the quaternary nitrogen to pyridine-like nitrogen ratio might be an important factor for improvement of the ORR activity.

Graphical abstractFig. ORR activities of nitrogen-doped carbon catalysts compared with TGA curve of iron 1,10-phenanthroline compound.Figure optionsDownload full-size imageDownload as PowerPoint slide