INDEX overpotential

From gas phase measurements CO is known to prefer top sites on all three low index faces, with the CO molecule perpendicular to the surface and bonded through the carbon end of the molecule except at high coverages (27). It is likely that HCOOH and COOH are adsorbed in a similar way. It is not likely that they could "enter the "troughs , which seems to be possible for anions. For Pt(100) on the other hand, upon sweep reversal and gradual oxide reduction, anions are immediately adsorbed on that "flat" surface. They block adsorption of HCOOH. Adsorption of anions decreases as potential becomes more negative. The oxidation of HCOOH commences and the rate increases as at more negative potentials, i.e. at lower overpotential. A competition between anions and HCOOH adsorption explains this apparently anomalous behaviour. The explanation of the "anomalous behaviour of the Pt(110) surface can be also found in the data for stepped surface vicinal to the (100) and (110) orientations. 

In the solutions containing gelatin, the morphology of the electrodeposits was also of the unorientated dispersion type. Consequently, the (002) orientation index of the deposited Zn depended on the overpotential for Zn deposition as shown in Fig.5(b). This result can be explained well by the Pangarov s two-dimensional nucleation theory (9) that the crystal orientation of the deposited metals is determined by the deposition overpotential of the metals. 

Theory of the Conversion of Resistance to an Overpotential. The correlation between impedance measurements and current/potential curve was first described by Wagner [2002] and is given schematically in Figure 4.5.40 and Figure 4.5.41. The polarization resistance of the cell Rceii) measured at [/ (index n = counter) corresponds to the tangent to the current/potential curve at that potential ([/ ). The polarization resistance of the cell is the impedance at frequencies near 0 Hz where only ohmic parts attract attention. To obtain the polarization resistance of the cell, one has to extrapolate the simulated impedance (model) at very low fre-... 

Bai L, Harrington DA, Conway BE. Behavior of overpotential-deposited species in Faradaic reactions-II. AC Impedance measurements on H2 evolution kinetics at activated and unactivated Pt eathodes. Electrochim Acta 1987 32(12) 1713-31. Markovic NM, Grgur BN, Ross PN. Temperature-dependent hydrogen electrochemistry on platinum low-index single-crystal surfaces in acid solutions. J PhysChemB 1997 101(27) 5405-13. 

Potential drops Acpi2 and Acp j across the metal-oxide and oxide-electrolyte interfaces and Aq>, across the oxide film for stationary (index s) and instationary (index i) conditions. Instationary conditions after potential increase cause a larger voltage drop Aipi within the layer and an overpotential Tij 3 at the oxide-electrolyte interface where oxide growth and the related O " production occur. (From Strehblow, H.-H., in Passivity of Metals, R.C. Alkire, D.M. Kolb, eds., Advances in Electrochemical Science and Engineering, Vol. 8, Wiley-VCH, Weinheim, Germany, pp. 271-374,2003.)... 

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