title: Unravelling the structure of electrocatalytically active Fe-N complexes in carbon for the oxygen reduction reaction.
abstract: Non-precious Fe/N co-modified carbon electrocatalysts have attracted great attention due to their high activity and stability in oxygen reduction reaction (ORR). Compared to iron-free N-doped carbon electrocatalysts, Fe/N-modified electrocatalysts show four-electron selectivity with better activity in acid electrolytes. This is believed relevant to the unique Fe-N complexes, however, the Fe-N structure remains unknown. We used o,m,p-phenylenediamine as nitrogen precursors to tailor the Fe-N structures in heterogeneous electrocatalysts which contain FeS and Fe3 C phases. The electrocatalysts have been operated for 5000 cycles with a small 39 mV shift in half-wave potential. By combining advanced electron microscopy and Mössbauer spectroscopy, we have identified the electrocatalytically active Fe-N6 complexes (FeN6, [Fe(III)(porphyrin)(pyridine)2]). We expect the understanding of the FeN6 structure will pave the way towards new advanced Fe-N based electrocatalysts.
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, Liaoning, 110016 (China); School of Chemistry and Life Science, Anshan Normal University, Anshan, Liaoning, 114005 (China).
authors.forename: Yansong
authors.initials: Y
authors.lastname: Zhu
authors.forename: Bingsen
authors.initials: B
authors.lastname: Zhang
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Wang
authors.forename: Dang Sheng
authors.initials: DS
authors.lastname: Su
keywords: Mössbauer spectroscopy; active sites; electrocatalysts; iron; oxygen reduction reaction