Noble-Metal-Free Fe–N/C Catalyst for Highly Efficient Oxygen Reduction Reaction under Both Alkaline and Acidic Conditions

• Published in: Journal of the American Chemical Society Vol. 136; no. 31; pp. 11027 - 11033
• Main Authors: Lin, Ling, Zhu, Qing, Xu, An-Wu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06.08.2014
• Subjects: active sites; catalysts; coordination polymers; durability; electrochemistry; iron; ligands; methanol; nitrogen; oxygen; perchloric acid; potassium hydroxide; pyrolysis; surface area
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/ja504696r

In this work, we report the synthesis and assessment of a new non-precious-metal oxygen reduction reaction (ORR) catalyst from pyrolysis of an iron-coordinated complex which manifests superior activity in both alkaline and acidic media. 11,11′-bis­(dipyrido­[3,2-a:2′,3′-c]­phenazinyl) (bidppz) was selected as a ligand for the formation of a nitrogen-rich iron-coordinated coordination polymer (Fe–bidppz) which forms a self-supporting catalyst containing high densities of nitrogen and iron doping by pyrolysis. The catalyst pyrolyzed at 800 °C (Fe–N/C-800) shows the highest ORR activity with onset and half-wave potentials of 923 and 809 mV in 0.1 M KOH, respectively, which are comparable to those of Pt/C (half-wave potential 818 mV vs RHE) at the same catalyst loading. Besides, the Fe–N/C-800 catalyst has an excellent ORR activity with onset and half-wave potentials only 38 and 59 mV less than those of the Pt/C catalyst in 0.1 M HClO4. The optimal Fe–N/C-800 catalyst displays much greater durability and tolerance of methanol than Pt/C. We propose that the Fe–N/C-800 catalyst has a considerably high density of surface active sites because Fe–N/C-800 possesses excellent ORR activity while its specific surface area is not so high. Electrochemical measurements show that the Fe–N/C-800 catalyst in KOH and HClO4 follows the effective four-electron-transfer pathway.