Simulation of electrochemical processes during oxygen evolution on Pb-MnO2 composite electrodes

dc.contributorAalto-yliopistofi
dc.contributorAalto Universityen
dc.contributor.advisorForsén, Oloffi
dc.contributor.authorSchmachtel, Sönke
dc.contributor.authorMurtomäki, Lassefi
dc.contributor.authorAromaa, Jarifi
dc.contributor.authorLundström, Marifi
dc.contributor.authorBarker, Michael H.fi
dc.contributor.departmentKemian laitosfi
dc.contributor.departmentDepartment of Chemistryen
dc.contributor.labLaboratory of Physical Chemistry and Electrochemistryen
dc.contributor.schoolKemian tekniikan korkeakoulufi
dc.contributor.schoolSchool of Chemical Technologyen
dc.date.accessioned2019-10-22T09:01:43Z
dc.date.available2019-10-22T09:01:43Z
dc.date.issued2017
dc.description.abstractThe geometric properties of Pb-MnO2 composite electrodes are studied, and a general formula ispresented for the length of the triple phase boundary (TPB) on two dimensional (2D) compositeelectrodes using sphere packing and cutting simulations. The difference in the geometrical properties of2D (or compact) and 3D (or porous) electrodes is discussed. It is found that the length of the TPB is theonly reasonable property of a 2D electrode that follows a 1/r particle radius relationship. Subsequently,sphere packing cuts are used to derive a statistical electrode surface that is the basis for the earlierproposed simulations of different electrochemical mechanisms. It is shown that two of the proposedmechanisms (conductivity and a two-step-two-material kinetic mechanism) can explain the currentincrease at Pb-MnO2 anodes compared to standard lead anodes.The results show that although MnO2 has low conductivity, when combined with Pb as the metal matrix,the behaviour of the composite is not purely ohmic but is also affected by activation overpotentials,increasing the current density close to the TPB. Current density is inversely proportional to the radius ofthe catalyst particles, matching with earlier experimental results. Contrary to earlier SECM experiments,mass transport of sulphuric acid is not likely to have any influence, as confirmed with simulations.A hypothetical two-step-two-material mechanism with intermediate H2O2 that reacts on both the Pbmatrix and MnO2 catalyst is studied. It was found that assuming quasi-reversible generation of H2O2followed by its chemical decomposition on MnO2, results are obtained that agree with the experiments.If the quasi-reversible formation of H2O2 occurs near the peroxide decomposition catalyst, currentincreases, leading to an active TPB and to the current density that scales with 1/r. It is furtheremphasised that both the Pb matrix and MnO2 catalyst are necessary and their optimum ratio dependson the used current density. Yet, additional experimental evidence is needed to support the postulatedmechanism.en
dc.description.versionPeer revieweden
dc.format.extent28+6
dc.format.mimetypeapplication/pdfen
dc.identifier.citationSchmachtel, Sönke & Murtomäki, Lasse & Aromaa, Jari & Lundström, Mari & Barker, Michael H. 2017. Simulation of electrochemical processes during oxygen evolution on Pb-MnO2 composite electrodes. Electrochimica Acta. Volume 245. 28+6.en
dc.identifier.urihttps://aaltodoc.aalto.fi/handle/123456789/40758
dc.identifier.urnURN:NBN:fi:aalto-201705103815
dc.language.isoenen
dc.publisherElsevieren
dc.relation.ispartofseriesElectrochimica Actafi
dc.relation.ispartofseriesVolume 245fi
dc.rights© 2017 Elsevier. This is the post print version of the following article: Schmachtel, Sönke & Murtomäki, Lasse & Aromaa, Jari & Lundström, Mari & Barker, Michael H. 2017. Simulation of electrochemical processes during oxygen evolution on Pb-MnO2 composite electrodes. Electrochimica Acta. Volume 245. 28+6, which has been published in final form at http://www.sciencedirect.com/science/article/pii/S001346861730912X. This post-print is published with permission from Elsevier under CC BY-NC-ND 4.0 license (http://creativecommons.org/licenses/by-nc-nd/4.0/)en
dc.rights.holderElsevier
dc.subject.keywordOxygen evolution on composite electrodeen
dc.subject.keywordmetal electrowinningen
dc.subject.keywordtriple phase boundary lengthen
dc.subject.keywordtwo-step two-material mechanismen
dc.subject.keyworddiffusion domain approachen
dc.subject.otherChemistryen
dc.subject.otherMetallurgyen
dc.subject.otherTechnologyen
dc.titleSimulation of electrochemical processes during oxygen evolution on Pb-MnO2 composite electrodesen
dc.typeA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessäfi
dc.type.dcmitypetexten
dc.type.versionPost printen
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