000125885 001__ 125885
000125885 005__ 20190717172516.0
000125885 0247_ $$2doi$$a10.5075/epfl-thesis-4181
000125885 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis4181-6
000125885 02471 $$2nebis$$a5641723
000125885 037__ $$aTHESIS
000125885 041__ $$aeng
000125885 088__ $$a4181
000125885 245__ $$binfluence of catayst loading and electrode kinetics$$aEffectiveness factor of thin-layer IrO2 electrocatalyst
000125885 269__ $$a2008
000125885 260__ $$bEPFL$$c2008$$aLausanne
000125885 300__ $$a176
000125885 336__ $$aTheses
000125885 520__ $$aDimensionally Stable Anodes (DSA®) are electrodes composed of a metal support and an oxide coating (catalyst). Particularly in this thesis, the Ti/IrO2 electrode was used for the study of the fraction of the surface which participates effectively in the investigated reactions (effectiveness factor, Ef ). Four reactions with different kinetics have been investigated: (a) Fe3+/Fe2+ (fast reaction), (b) O2 and (c) Cl2 evolutions (slow reactions), and (d) isopropanol oxidation (complex reaction involving redox catalysis). This study has allowed us to apply for the first time in electrocatalysis the term, effectiveness factor, Ef , used before in other fields like in heavy metals recovery with 3D electrodes and in heterogeneous catalysis. On the other hand, in order to achieve the main objective of this thesis, an analytical and a qualitative approach was proposed. Furthermore, the Ti/IrO2 electrodes were characterized electrochemically using the cyclic voltammetry (CV) technique in which the voltammetric charge was measured at different potential scan rates, potential windows, and electrolyte temperatures using various Ti/IrO2 loadings. From the voltammetric charge, two contributions were found. The first contribution is related to the double layer capacitance and the second with the redox couples present on the electrode surface. The first reaction investigated in this work was the Fe3+/Fe2+ redox couple. In the first part of the investigation of this reaction, the CV technique was used; however, some issues related to the uncompensated electrolyte resistance were encountered. Therefore the effectiveness factor for this particular case was not possible to obtain. On the other hand, using rotating Ti/IrO2 disk electrodes (RDE) for the same reaction, the effectiveness factor, Ef , has been estimated, however, this value is much lower than the predicted one. The other investigated reactions in this work were O2 and Cl2 evolutions. The investigated kinetics of both reactions showed that the evolution of chlorine is much faster than that of oxygen. The effectiveness factor, Ef , for the oxygen evolution was close to the unity for all IrO2 loadings, contrary to the chlorine reaction that decreased with the loading. This behaviour was predicted according to what is given in the analytical approach. The last reaction investigated in this work was the oxidation of isopropanol. In this case a model was proposed based on three main reactions: Electrochemical IrO2 oxidation to IrO3, chemical oxidation of isopropanol via IrO3, and chemical decomposition of IrO3 to IrO2. The effectiveness factor, for the electrochemical reaction seemed not to correlate with the loading, whereas for the chemical one, it diminished with the loading.
000125885 6531_ $$aTi/IrO2
000125885 6531_ $$avoltammetric charge
000125885 6531_ $$areal surface area
000125885 6531_ $$aeffectiveness factor
000125885 6531_ $$aroughness factor
000125885 6531_ $$aTi/IrO2
000125885 6531_ $$acharge voltamétrique
000125885 6531_ $$asurface réelle
000125885 6531_ $$afacteur d'efficacité
000125885 6531_ $$afacteur de rugosité
000125885 700__ $$aHerrera Calderon, Erika
000125885 720_2 $$aComninellis, Christos$$edir.$$g104807$$0240416
000125885 720_2 $$aWüthrich, Rolf$$edir.
000125885 8564_ $$zTexte intégral / Full text$$yTexte intégral / Full text$$uhttps://infoscience.epfl.ch/record/125885/files/EPFL_TH4181.pdf$$s2497167
000125885 909C0 $$xU10173$$pGGEC$$0252005
000125885 909C0 $$pLSRO$$0252016
000125885 909CO $$pDOI$$ooai:infoscience.tind.io:125885$$qDOI2$$qGLOBAL_SET$$pSTI$$pthesis$$pthesis-bn2018
000125885 918__ $$dEDPR$$cISIC$$aSTI
000125885 919__ $$aGGEC
000125885 919__ $$aLSRO1
000125885 920__ $$b2008
000125885 970__ $$a4181/THESES
000125885 973__ $$sPUBLISHED$$aEPFL
000125885 980__ $$aTHESIS