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Pt/electrolyte interface

The Pt surface electro-oxidation process observed in the absence of dioxygen to form chemisorbed OH from water is driven by the potential difference at the Pt/ electrolyte interface, according to the reaction... [Pg.14]

Anderson AB. 2002. O2 reduction and CO oxidation at the Pt-electrolyte interface. The role of H2O and OH adsorption bond strengths. Electrochim Acta 47 3759-3763. [Pg.307]

The total number of molecules produced or consumed in the reaction is proportional to the surface area of the Pt/electrolyte interface. The plain interface shown in Figure 1.2 would give a very small current suitable for electrochemical studies, but would be of no practical interest for energy conversion devices. In practical fuel cells, the Pt/electrolyte interface should be as large as possible. This is achieved by mixing tiny carbon-supported catalyst particles with the polymer electrol3de and filling voids of carbon cloth or paper with this mixture. [Pg.7]

The polymer electroljde can be thought of as a plasma in which positive charges (protons) can move under the action of the electric field, whereas the negative charges are fixed at the polymer backbone. In the presence of feed molecules, positive and negative charges at the Pt/electrolyte interface separate and an electric double layer forms (Figure 1.1). [Pg.8]

However, this apparent simplicity hides a lot of complex and poorly understood processes inside the cell. Feed molecule ionization and ion recombination run on a surface of precious catalyst particles (Pt, as a rule), which is in contact with the electrolyte. A giant electric field arises at the Pt/electrolyte interface. The electrochemical reactions in this environment have been intensively investigated for more than fifty years, but their mechanisms still remain controversial. [Pg.299]

Figure 3.51 shows the impedance spectra for a Pt/FTO sandwich cell at different bias potentials reported by Hauch and Georg.The impedance element on the left of the spectrum (high frequencies) is the Pt/ electrolyte interface (charge-transfer resistance and double layer capacitance) on the right (low frequencies) there is the Nernst diffusion impedance. The diameter of the high frequency semicircle in the impedance... [Pg.163]

Hauch and George have suggested the mechanism below for oxidation of r at the Pt electrode from analysis of the impedance measurements and Langmuir isotherms for the Pt/electrolyte interface. The ratedetermining step of the suggested mechanism is the oxidation of iodide at the Pt surface. [Pg.164]

The reference electrode-solid electrolyte interface must also be non-polarizable, so that rapid equilibration is established for the electrocatalytic charge-transfer reaction. Thus it is generally advisable to sinter the counter and reference electrodes at a temperature which is lower than that used for the catalyst film. Porous Pt and Ag films exposed to ambient air have been employed in most previous NEMCA studies.1,19... [Pg.118]

As already analysed in Chapter 5, once the backspillover species originating from the solid electrolyte have migrated at the metal/gas interface, then they act as normal (chemical) promoters for catalytic reactions. For example, Lambert and coworkers via elegant use of XPS18 have shown that the state of sodium introduced via evaporation on a Pt surface interfaced with P"-A1203 is indistinguishable from Na5+ introduced on the same Pt surface via negative (cathodic) potential application. [Pg.283]

Figure A.l. Schematic presentation of a catalytic cylindrical Pt cluster interfaced with an O2 -conducting solid electrolyte (YSZ) showing the flux, N, of the promoting species. Figure A.l. Schematic presentation of a catalytic cylindrical Pt cluster interfaced with an O2 -conducting solid electrolyte (YSZ) showing the flux, N, of the promoting species.
Previously, we have proposed that SFG intensity due to interfacial water at quartz/ water interfaces reflects the number of oriented water molecules within the electric double layer and, in turn, the double layer thickness based on the p H dependence of the SFG intensity [10] and a linear relation between the SFG intensity and (ionic strength) [12]. In the case of the Pt/electrolyte solution interface the drop in the potential profile in the vicinity ofelectrode become precipitous as the electrode becomes more highly charged. Thus, the ordered water layer in the vicinity of the electrode surface becomes thiimer as the electrode is more highly charged. Since the number of ordered water molecules becomes smaller, the SFG intensity should become weaker at potentials away from the pzc. This is contrary to the experimental result. [Pg.81]

TR-SFG measurements at a Pt electrode/electrolyte interface covered with a CO monolayer excited by the irradiation of picosecond visible pulses showed that the... [Pg.88]

Akemann W, Friedrich KA, Linke U, Stimming U. 1998. The catal)4ic oxidation of carbon monoxide at the platinum/electrolyte interface investigated by optical second harmonic generation (SHG) Comparison of Pt(l 11) and Pt(997) electrode surfaces. Surf Sci 404 571-575. [Pg.403]

The adsorption of CO on Pt is perhaps the most throughly studied system using vibrational spectroscopy. Studies have been made using both supported catalysts (2-5) and single crystals (5-10). Sample environments have included gas phase, vacuum, and aqueous solution (11-13). The similarities between many of these results have led to a remarkably unified understanding of CO adsorption phenomena in all three environments. Features which are relevant to further studies of the metal/electrolyte interface are summarized briefly ... [Pg.370]

Role of the bulk transport path. In section 3 we saw that for Pt the dissociation of oxygen and transport of reactive intermediates to the electrode/ electrolyte interface is confined to the material surface. With mixed conductors, it is possible for oxygen reduced at the surface to be transported through the bulk of the material to the electrode/ electrolyte interface. If bulk transport is facile, this path may dominate, extending both the accessible surface for O2 reduction as well as broadening the active charge-transfer area from the TPB to include the entire solid—solid contact area. [Pg.576]

Like all cathodes, early electrochemical kinetic studies of LSM focused heavily on steady-state d.c. characteristics, attempting to extract mechanistic information from the Tand F02 dependence of linear and Tafel parameters.As recently as 1997, some workers have continued to support a view that LSM is limited entirely by electrochemical kinetics at the LSM/electrolyte Interface based on this type of analysis. However, as we have seen for other materials (including Pt), the fact that an electrode obeys Butler—Volmer kinetics means little in terms of identifying rate-limiting phenomena or in determining how close the reaction occurs to the TPB. To understand LSM at a nonempirical level, we must examine other techniques and results. [Pg.578]

In this type of cell both electrodes are immersed in the same constant pH solution. An illustrative cell is [27,28] n-SrTiOs photoanode 9.5-10 M NaOH electrolyte Pt cathode. The underlying principle of this cell is production of an internal electric field at the semiconductor-electrolyte interface sufficient to efficiently separate the photogenerated electron-hole pairs. Subsequently holes and electrons are readily available for water oxidation and reduction, respectively, at the anode and cathode. The anode and cathode are commonly physically separated [31-34], but can be combined into a monolithic structure called a photochemical diode [35]. [Pg.124]


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Electrolyte interface

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