Elucidating the mechanism of the oxygen reduction reaction for pyrolyzed Fe-N-C catalysts in basic media

• DOI: 10.1016/j.elecom.2019.04.005
• Publication Date: 2019-04-05T09:27:46Z
• Authors: César Zúñiga; Christian Candia-...; Ricardo Venegas; Karina Muñoz; Jonathan Urra; María Sánchez-Are...; José F. Marco; José H. Zagal; Francisco J. Recio
• Keywords: Chemistry; Industrial electrochemistry; Pyrolyzed catalysts; Cyanide poisoning; Mechanism; Redox potential; QD1-999; 01 natural sciences; TP250-261; Oxygen reduction reaction; 0104 chemical sciences

The study of non-precious metal catalysts (NPMCs) as alternatives to platinum for oxygen reduction is crucial if the use fuel cells become more widespread. Among NPMCs, pyrolyzed (Fe-N-C) are particularly promising in both basic and acid media. characterization active sites understanding reaction (ORR) mechanism design Fe-N-C catalysts. In this study, we have tested involvement centre ORR process at pH 13 two iron porphyrins. present a FeN4 site structure similar that porphyrin precursors. Regarding mechanism, found evidence role Fe(II) centres. There direct relation between Fe(III)/(II) redox transition onset potential ORR, showing electrogeneration from Fe(III)OH– controls catalysis. poisoning centres with CN− induces decrease activity. However, H2O2 generation remains unchanged. Tafel plots show different slopes high low overpotentials. Based on these results, propose mechanisms, dependent FeO2 binding energy.