Towards identifying platinum anchor sites on carbon via a model electrochemical system

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dc.contributor.advisorLevecque, Pieter
dc.contributor.advisorScherer, Günther
dc.contributor.authorFortuin, Adrian Charles
dc.date.accessioned2018-08-30T07:03:10Z
dc.date.available2018-08-30T07:03:10Z
dc.date.issued2018
dc.date.updated2018-08-15T09:14:02Z
dc.description.abstractThe interaction between Pt and its carbon support was investigated by a model electrochemical system. This entailed aggressively oxidising a two-dimensional carbon substrate, i.e. highly orientated pyrolytic graphite (HOPG) and mirror finish graphite (MFG) quartz crystal, to incorporate oxygen terminated groups into the graphitic matrix. This study focusses on potential cycling to determine the mobility of Pt across these carbon surfaces and the effect of the Pt anchoring to carbon on the electrocatalyst durability. This work incorporates both a conventional three electrode electrochemical setup and the use of the electrochemical quartz crystal nano-balance (EQCN). The objectives of this study were to better understand the Pt mobility across the carbon substrate surface and to gain insight into the solid-liquid interface of Pt dissolution due to potential cycling. Initial results on HOPG as discussed in chapter 2, indicated minimal Pt dissolution of between 13% and 15% of total electrochemical active surface area loss. These results, however, did not provide adequate evidence to conclusively determine the extent of Pt mobility on the carbon surface and the effect of oxygen terminated groups in hindering Pt dissolution. In order to gain a more thorough understanding of the Pt dissolution processes, the use of the EQCN technique was utilised. Firstly, it was shown that the mirror finished graphite quartz crystals used in the EQCN technique, are qualitatively comparable to the electrochemical measurements recorded with the HOPG samples. Secondly, potential cycling under the same conditions as HOPG produced similar electrochemical results. The frequency response curves from the EQCN yielded the most promising results. This study showed, qualitatively, that the surface of Pt is non-monotonic, and that the surface charge changes with increased potential cycling. Pt/MFG-A had consistent frequency responses over the entire potential range during Pt dissolution, thus, with the above understanding of surface charge, it is concluded that acid treated carbon substrates show a stronger affinity for Pt anchoring.
dc.identifier.apacitationFortuin, A. C. (2018). <i>Towards identifying platinum anchor sites on carbon via a model electrochemical system</i>. (). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/28347en_ZA
dc.identifier.chicagocitationFortuin, Adrian Charles. <i>"Towards identifying platinum anchor sites on carbon via a model electrochemical system."</i> ., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2018. http://hdl.handle.net/11427/28347en_ZA
dc.identifier.citationFortuin, A. 2018. Towards identifying platinum anchor sites on carbon via a model electrochemical system. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Fortuin, Adrian Charles AB - The interaction between Pt and its carbon support was investigated by a model electrochemical system. This entailed aggressively oxidising a two-dimensional carbon substrate, i.e. highly orientated pyrolytic graphite (HOPG) and mirror finish graphite (MFG) quartz crystal, to incorporate oxygen terminated groups into the graphitic matrix. This study focusses on potential cycling to determine the mobility of Pt across these carbon surfaces and the effect of the Pt anchoring to carbon on the electrocatalyst durability. This work incorporates both a conventional three electrode electrochemical setup and the use of the electrochemical quartz crystal nano-balance (EQCN). The objectives of this study were to better understand the Pt mobility across the carbon substrate surface and to gain insight into the solid-liquid interface of Pt dissolution due to potential cycling. Initial results on HOPG as discussed in chapter 2, indicated minimal Pt dissolution of between 13% and 15% of total electrochemical active surface area loss. These results, however, did not provide adequate evidence to conclusively determine the extent of Pt mobility on the carbon surface and the effect of oxygen terminated groups in hindering Pt dissolution. In order to gain a more thorough understanding of the Pt dissolution processes, the use of the EQCN technique was utilised. Firstly, it was shown that the mirror finished graphite quartz crystals used in the EQCN technique, are qualitatively comparable to the electrochemical measurements recorded with the HOPG samples. Secondly, potential cycling under the same conditions as HOPG produced similar electrochemical results. The frequency response curves from the EQCN yielded the most promising results. This study showed, qualitatively, that the surface of Pt is non-monotonic, and that the surface charge changes with increased potential cycling. Pt/MFG-A had consistent frequency responses over the entire potential range during Pt dissolution, thus, with the above understanding of surface charge, it is concluded that acid treated carbon substrates show a stronger affinity for Pt anchoring. DA - 2018 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2018 T1 - Towards identifying platinum anchor sites on carbon via a model electrochemical system TI - Towards identifying platinum anchor sites on carbon via a model electrochemical system UR - http://hdl.handle.net/11427/28347 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/28347
dc.identifier.vancouvercitationFortuin AC. Towards identifying platinum anchor sites on carbon via a model electrochemical system. []. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2018 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/28347en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Chemical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherchemical engineering
dc.subject.otherplatinum anchor sites
dc.subject.otherelectrochemical system
dc.titleTowards identifying platinum anchor sites on carbon via a model electrochemical system
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhD
uct.type.filetypeText
uct.type.filetypeImage
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