Please use this identifier to cite or link to this item: https://doi.org/10.15480/882.3507
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dc.contributor.authorSilva Olaya, Alex Ricardo-
dc.contributor.authorZandersons, Birthe-
dc.contributor.authorWittstock, Gunther-
dc.date.accessioned2021-05-04T11:24:16Z-
dc.date.available2021-05-04T11:24:16Z-
dc.date.issued2021-04-09-
dc.identifier.citationElectrochimica Acta 383: 138348 (2021-07-01)de_DE
dc.identifier.issn0013-4686de_DE
dc.identifier.urihttp://hdl.handle.net/11420/9425-
dc.description.abstractNanoporous gold (NPG) obtained by potentiostatic dealloying of an AuAg master alloy was pulverized, filled into a cavity microelectrode and its surface electrochemistry was investigated in NaOH and KOH solutions. This method yielded highly resolved undistorted voltammograms of this polycrystalline material with clear evidences for surface segregation of Ag during storage in air. One cycle in 0.1 M H SO can remove most of the residual Ag from the surface as evidenced by voltammetry after back transfer to alkaline solution and by X-ray photoelectron spectroscopy (XPS). After removal of residual Ag from the surface, the surface undergoes rephasing forming wider 111 and 110 terraces as evidenced by Pb underpotential deposition (UPD). By adjustment of the bulk concentration of Pb species, a selective partial coverage of the high internal surface area of NPG could be intentionally adjusted. Lead species remain attached to the NPG surface at potentials positive of the UPD regions either as plumbates or Pb species as evidenced by XPS. Those tools enable to disentangle effects on the electrocatalysis of the methanol oxidation reaction (MOR) in different potential regions for 1 M methanol in different concentrations of NaOH and KOH. The MOR commences at lower potentials in the presence of residual Ag. At very high potential, the presence of Ag species promotes the oxidation to CO /CO . Tafel analysis after selective blocking of specific facets shows that the 110 terraces promote especially the first step of MOR while the 111 terraces enhance the rate of further steps that are rate-limiting at higher potentials. While high coverages by Pb UPD layers or adsorbed plumbate anions inhibit electrooxidation, the behavior of NPG electrodes with low coverages of Pb species is reminiscent to NPG electrodes with residual Ag. This could be caused by promoting the methoxide and/or OH adsorption at low overpotentials and catalyzing complete oxidation by a surface bound Pb species at higher potentials. The catalytic currents increase with base concentration and are higher for KOH compared to NaOH. Comparable effects of base concentration on the parameters of the Tafel lines suggest that this effect is a result of slightly stronger deprotonation of methanol in bulk KOH solutions. 2 4 2 3 II IV 2- - IVen
dc.description.sponsorshipDeutsche Forschungsgemeinschaft (DFG)de_DE
dc.language.isoende_DE
dc.publisherElsevierde_DE
dc.relation.ispartofElectrochimica actade_DE
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/de_DE
dc.subjectElectrocatalysisde_DE
dc.subjectMethanol oxidationde_DE
dc.subjectNanoporous goldde_DE
dc.subjectSurface structurede_DE
dc.subjectUnder potential depositionde_DE
dc.subject.ddc600: Technikde_DE
dc.titleEffect of the residual silver and adsorbed lead anions towards the electrocatalytic methanol oxidation on nanoporous gold in alkaline mediade_DE
dc.typeArticlede_DE
dc.identifier.doi10.15480/882.3507-
dc.type.diniarticle-
dcterms.DCMITypeText-
tuhh.identifier.urnurn:nbn:de:gbv:830-882.0133661-
tuhh.oai.showtruede_DE
tuhh.abstract.englishNanoporous gold (NPG) obtained by potentiostatic dealloying of an AuAg master alloy was pulverized, filled into a cavity microelectrode and its surface electrochemistry was investigated in NaOH and KOH solutions. This method yielded highly resolved undistorted voltammograms of this polycrystalline material with clear evidences for surface segregation of Ag during storage in air. One cycle in 0.1 M H SO can remove most of the residual Ag from the surface as evidenced by voltammetry after back transfer to alkaline solution and by X-ray photoelectron spectroscopy (XPS). After removal of residual Ag from the surface, the surface undergoes rephasing forming wider 111 and 110 terraces as evidenced by Pb underpotential deposition (UPD). By adjustment of the bulk concentration of Pb species, a selective partial coverage of the high internal surface area of NPG could be intentionally adjusted. Lead species remain attached to the NPG surface at potentials positive of the UPD regions either as plumbates or Pb species as evidenced by XPS. Those tools enable to disentangle effects on the electrocatalysis of the methanol oxidation reaction (MOR) in different potential regions for 1 M methanol in different concentrations of NaOH and KOH. The MOR commences at lower potentials in the presence of residual Ag. At very high potential, the presence of Ag species promotes the oxidation to CO /CO . Tafel analysis after selective blocking of specific facets shows that the 110 terraces promote especially the first step of MOR while the 111 terraces enhance the rate of further steps that are rate-limiting at higher potentials. While high coverages by Pb UPD layers or adsorbed plumbate anions inhibit electrooxidation, the behavior of NPG electrodes with low coverages of Pb species is reminiscent to NPG electrodes with residual Ag. This could be caused by promoting the methoxide and/or OH adsorption at low overpotentials and catalyzing complete oxidation by a surface bound Pb species at higher potentials. The catalytic currents increase with base concentration and are higher for KOH compared to NaOH. Comparable effects of base concentration on the parameters of the Tafel lines suggest that this effect is a result of slightly stronger deprotonation of methanol in bulk KOH solutions. 2 4 2 3 II IV 2- - IVde_DE
tuhh.publisher.doi10.1016/j.electacta.2021.138348-
tuhh.publication.instituteWerkstoffphysik und -technologie M-22de_DE
tuhh.identifier.doi10.15480/882.3507-
tuhh.type.opus(wissenschaftlicher) Artikel-
dc.type.driverarticle-
dc.type.casraiJournal Article-
tuhh.container.volume383de_DE
dc.relation.projectFOR 2213: Teilprojekt "Auf Quantenmechanik basierende, quantitative Modellierung von Metalllegierungsoberflächen als Funktion ihrer Umgebung"de_DE
dc.relation.projectFOR 2213: Teilprojekt "Gefügeentwicklung und Auswirkungen der Mechanik auf die Katalyse"de_DE
dc.rights.nationallicensefalsede_DE
dc.identifier.scopus2-s2.0-85104482932de_DE
tuhh.container.articlenumber138348de_DE
local.status.inpressfalsede_DE
local.type.versionpublishedVersionde_DE
local.funding.infoThe support of Deutsche Forschungsgemeinschaft is gratefully acknowledge for funding the Research Group FOR2213-255613253 [subprojects 3 and 4] as well as for partial funding of the central facilities of the School of Mathematics and Science for SEM (INST 184/107-1 FUGG) and XPS instrumentation (INST 184/144-1 FUGG).de_DE
item.grantfulltextopen-
item.openairetypeArticle-
item.creatorOrcidSilva Olaya, Alex Ricardo-
item.creatorOrcidZandersons, Birthe-
item.creatorOrcidWittstock, Gunther-
item.openairecristypehttp://purl.org/coar/resource_type/c_6501-
item.fulltextWith Fulltext-
item.cerifentitytypePublications-
item.mappedtypeArticle-
item.languageiso639-1en-
item.creatorGNDSilva Olaya, Alex Ricardo-
item.creatorGNDZandersons, Birthe-
item.creatorGNDWittstock, Gunther-
crisitem.funder.funderid501100001659-
crisitem.funder.funderrorid018mejw64-
crisitem.project.funderDeutsche Forschungsgemeinschaft (DFG)-
crisitem.project.funderDeutsche Forschungsgemeinschaft (DFG)-
crisitem.project.funderid501100001659-
crisitem.project.funderid501100001659-
crisitem.project.funderrorid018mejw64-
crisitem.project.funderrorid018mejw64-
crisitem.project.grantnoMU 1648/7-1-
crisitem.project.grantnoWE 1424/17-1-
crisitem.author.deptWerkstoffphysik und -technologie M-22-
crisitem.author.orcid0000-0003-2915-6618-
crisitem.author.orcid0000-0002-8526-5803-
crisitem.author.orcid0000-0002-6884-5515-
crisitem.author.parentorgStudiendekanat Maschinenbau-
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