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Oxygen Reduction Reaction Activity in Non-Precious Single-Atom (M−N/C) Catalysts − Contribution of Metal and Carbon/Nitrogen Framework-Based Sites

  • We examine the performance of a number of single-atom M−N/C electrocatalysts with a common structure in order to deconvolute the activity of the framework N/C support from the metal M−N4 sites in M−N/Cs. The formation of the N/C framework with oordinating nitrogen sites is performed using zinc as a templating agent. After the formation of the electrically conducting carbon−nitrogen metal-coordinating network, we (trans)metalate with different metals producing a range of different catalysts (Fe−N/C, Co−N/C, Ni−N/C, Sn−N/C, Sb−N/C, and Bi−N/C) without the formation of any metal particles. In these materials, the structure of the carbon/nitrogen framework remains unchanged-only the coordinated metal is substituted. We assess the performance of the subsequent catalysts in acid, near-neutral, and alkaline environments toward the oxygen reduction reaction (ORR) and ascribe and quantify the performance to a combination of metal site activity and activity of the carbon/nitrogen framework. TheWe examine the performance of a number of single-atom M−N/C electrocatalysts with a common structure in order to deconvolute the activity of the framework N/C support from the metal M−N4 sites in M−N/Cs. The formation of the N/C framework with oordinating nitrogen sites is performed using zinc as a templating agent. After the formation of the electrically conducting carbon−nitrogen metal-coordinating network, we (trans)metalate with different metals producing a range of different catalysts (Fe−N/C, Co−N/C, Ni−N/C, Sn−N/C, Sb−N/C, and Bi−N/C) without the formation of any metal particles. In these materials, the structure of the carbon/nitrogen framework remains unchanged-only the coordinated metal is substituted. We assess the performance of the subsequent catalysts in acid, near-neutral, and alkaline environments toward the oxygen reduction reaction (ORR) and ascribe and quantify the performance to a combination of metal site activity and activity of the carbon/nitrogen framework. The ORR activity of the carbon/nitrogen framework is about 1000-fold higher in alkaline than it is in acid, suggesting a change in mechanism. At 0.80 VRHE, only Fe and Co contribute ORR activity significantly beyond that provided by the carbon/nitrogen framework at all pH values studied. In acid and near-neutral pH values (pH 0.3 and 5.2, respectively), Fe shows a 30-fold improvement and Co shows a 5-fold improvement, whereas in alkaline pH (pH 13), both Fe and Co show a 7-fold improvement beyond the baseline framework activity. The site density of the single metal atom sites is estimated using the nitrite adsorption and stripping method. This method allows us to deconvolute the framework sites and metal-based active sites. The framework site density of catalysts is estimated as 7.8 × 1018 sites g−1. The metal M−N4 site densities in Fe−N/C and Co−N/C are 9.4 × 1018 sites−1 and 4.8 × 1018 sites g−1, respectively.zeige mehrzeige weniger

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Metadaten
Autor*innen:M. Gong, Asad MehmoodORCiD, B. Ali, K.-W. Nam, A. KucernakORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):ACS Catalysis
Jahr der Erstveröffentlichung:2023
Organisationseinheit der BAM:3 Gefahrgutumschließungen; Energiespeicher
3 Gefahrgutumschließungen; Energiespeicher / 3.6 Elektrochemische Energiematerialien
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Verlag:American Chemical Society
Jahrgang/Band:13
Ausgabe/Heft:10
Erste Seite:6661
Letzte Seite:6674
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Angewandte Physik
Freie Schlagwörter:Active site density; Fuel cells; M−N/Cs; Oxygen reduction reaction; PGM-free catalysts; Single-atom catalysts
Themenfelder/Aktivitätsfelder der BAM:Energie
DOI:10.1021/acscatal.3c00356
URN:urn:nbn:de:kobv:b43-575640
ISSN:2155-5435
Verfügbarkeit des Dokuments:Datei für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - CC BY - Namensnennung 4.0 International
Datum der Freischaltung:31.05.2023
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:31.05.2023
Schriftenreihen ohne Nummerierung:Wissenschaftliche Artikel der BAM
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