Fe–N∕C Oxygen Reduction Catalysis Prepared by Covalent Attachment of 1,10-Phenanthroline to a Carbon Surface

Abstract

Nonprecious metal catalysts ͑NPMC͒ for the oxygen reduction reaction were prepared by surface modification of a carbon black with 5,6-diamino-1,10-phenanthroline through diazonium and benzimidazole coupling chemistry. Both methodologies covalently attach 1,10-phenanthroline to the surface. Oxygen-free cyclic voltammograms ͑CV͒ obtained for these modified carbons showed a clearly defined redox peak at ca. 650 mV versus normal hydrogen electrode, which we attribute to phenanthroline-type groups on the carbon surface. Introduction of Fe and subsequent pyrolysis at 700°C under a NH 3 /N 2 atmosphere yielded catalysts that were highly active toward the oxygen reduction reaction. The redox peak at 650 mV was present in the oxygen-free CVs for the most active catalysts, though less intense. Nevertheless, this indicates the presence pyridinic-type active sites in the heat treated catalysts and may be a useful tool in the study of NPMC.

Electrochemical Formation of an Ultrathin Electroactive Film from 1,10-Phenanthroline on a Glassy Carbon Electrode in Acidic Electrolyte

“…They could be tentatively attributed to the redox behavior of pyridinic-type species present at the carbon electrode surface. 11,19 However, this is unlikely because a redox response is not observed for a glassy carbon electrode immersed into solution of 1 mM phenanthroline in 0.1 M H 2 SO 4 and cycled between 0 and 1.2 V (not shown). The chemical transformation occurring during these electrochemical processes and the nature of the resulting films will be investigated by time-of-flight secondary ion mass spectroscopy.…”

“…26 1,10-Phenanthroline can also be electrografted on a substrate by electrochemical reduction of the corresponding diazonium cations. 11,27 Very recently, the electrochemical reduction of 5bromo-1,10-phenanthroline afforded the generation of 1,10phenanthroline radical and the subsequent passivation of a gold electrode. 28 Despite great interest in the chemistry of metallic 1,10-phenanthroline complexes, there is a limited number of reports on the covalent modification of an electrode surface with 1,10-phenanthroline by using only phenanthroline as reagent.…”

Effect of Transition Metals on the Oxygen Reduction Reaction Activity at Metal‐N3/C Active Sites

“…Interestingly, after heat treatment the V-tpy/Sn-700 sample shows a drastic decrease in nitrogen, almost half of what it was before heat treatment. Further indicating that the metal acts to help retain nitrogen in the pyridinic state, without it the nitrogen functionalities do not survive well [32] ( Figure S5). There is still a significant amount of tin in the sample, however, slightly less than the original V-tpy/ Sn sample.…”

“…While it has been reported in the literature that a N 3 site might be a defect to the most widely accepted active site, we deliberately formed these sites specifically on the surface to assess the activity of sites that differ from the N 2+2 type site [28–31] . A surface modification approach was adapted to functionalize the surface with the nitrogen and then iron was added to create coordination motifs on the surface [27,32] . Next, we investigated the role that carbon supports played on our novel catalyst design and found that the least porous support (Vulcan XC‐72 carbon) yielded the highest activity [33] .…”

“…[28][29][30][31] A surface modification approach was adapted to functionalize the surface with the nitrogen and then iron was added to create coordination motifs on the surface. [27,32] Next, we investigated the role that carbon supports played on our novel catalyst design and found that the least porous support (Vulcan XC-72 carbon) yielded the highest activity. [33] In this work we altered the nature of the transition metal of the N 3 site to study metal influence in our novel N 3 site for its effectiveness for the ORR.…”