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Differentiation and quantification of surface acidities on MWCNTs by indirect potentiometric titration

  • Wet-chemically oxidized carbon nanotubes (CNTs) generally exhibit both covalently-bound acidic functional groups on the surface and surface-adsorbed acidic substances, i.e. carbonaceous CNT fragments from the oxidation procedure. Direct potentiometric titration of oxidizable high surface area materials with dynamically desorbing acidic fragments is slow and inaccurate. Adsorbed acidic fragments are deprotonated by sodium hydroxide and form anions in solution which is not the case for covalently bound acidic groups on the CNTs, so the following filtration after NaOH treatment separates desorbable acidic substances from non-desorbable or covalently bound groups. For a known concentration of NaOH, titration of the eluate with hydrochloric acid (HCl) allows determination of the concentrations of both types of acidities. However, contrary to reports in the literature, the NaOH consumed by non-desorbed acidic groups has to be accounted for and impedes distinction of desorbed acidic groupsWet-chemically oxidized carbon nanotubes (CNTs) generally exhibit both covalently-bound acidic functional groups on the surface and surface-adsorbed acidic substances, i.e. carbonaceous CNT fragments from the oxidation procedure. Direct potentiometric titration of oxidizable high surface area materials with dynamically desorbing acidic fragments is slow and inaccurate. Adsorbed acidic fragments are deprotonated by sodium hydroxide and form anions in solution which is not the case for covalently bound acidic groups on the CNTs, so the following filtration after NaOH treatment separates desorbable acidic substances from non-desorbable or covalently bound groups. For a known concentration of NaOH, titration of the eluate with hydrochloric acid (HCl) allows determination of the concentrations of both types of acidities. However, contrary to reports in the literature, the NaOH consumed by non-desorbed acidic groups has to be accounted for and impedes distinction of desorbed acidic groups via their pKa values. Results are presented of a study on the information content and the reliability of indirect potentiometric Boehm titration for different oxidized multi-walled CNTs.zeige mehrzeige weniger

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Metadaten
Autor*innen:Sven Hanelt, Guillermo Orts Gil, Jörg Florian Friedrich, Asmus Meyer-Plath
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Carbon
Jahr der Erstveröffentlichung:2011
Verlag:Pergamon Press
Verlagsort:New York, NY
Jahrgang/Band:49
Ausgabe/Heft:9
Erste Seite:2978
Letzte Seite:2988
DOI:10.1016/j.carbon.2011.03.016
ISSN:0008-6223
ISSN:1873-3891
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:19.02.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:09.05.2011
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