Potential of maximum

Figure 7.10 Potential of maximum entropy (PME) of a Pt(lll) electrode modified by Bi, Pb, Se, and S deposition in 1 mM HCIO4 + 0.1 M KCIO4 solution, as a function of adatom coverage. The dashed, zero-slope line corresponds to the averaged reference PME value of unmodified Pt(lll). The cartoons show the schematic interpretation for the effect of the adatoms at high coverage on the potential transients. (Reprinted with permission from Garcia-Araez et al. [2008].)...

Climent V, Coles BA, Compton RG. 2002b. Coulostatic potential transients induced by laser heating of a Pt(lll) single-crystal electrode in aqueous acid solutions. Rate of hydrogen adsorption and potential of maximum entropy. J Phys Chem B 106 5988-5996. 

Climent V, Garcia-Araez N, Compton RG, Feliu JM. 2006. Effect of deposited bismuth on the potential of maximum entropy of Pt(lll) single-crystal electrodes. J Phys Chem B 110 21092-21100. 

Figure 10.4. Adsorption isotherms for n-decylamine on Ni, Fe, Cu, Pb, and Pt at the potential of maximum adsorption. (From Ref. 5, with permission from the Electrochemical Society.)...

Adsorption of -hexanol on Ag(lOO) and Ag(llO) from aqueous 0.05 M KCIO4 solutions has been studied by Foresti et al. [59], who performed capacitive charge measurements and compared the results with those obtained for Ag(lll). The calculated adsorption free energy (at the potential of maximum adsorption) was = —17.7 kJ mol for Ag(lOO),... 

A simple equation results if we use the BDM isotherm for potentials far removed from the potential of maximum adsorption. In this case the high field aligns all water molecules in one orientation, leading to Z +. The term Za in the exponent of Eq. 27J will be nearly constant and small compared to pF, so that this equation can be simplified to ... 

The corresponding plots of the relative surface excess as a function of potential appear in Fig. 12H. We note that the potential of maximum adsorption (which is usually denoted for simp-... 

This is the BDM isotherm, not taking into account the small shift between the potential of zero charge and the potential of maximum adsorption, which arises from the different chemical energies of interaction of water with the surface in its two allowed orientations. 

In Fig. 49 the band center frequency is plotted against the potential for the 1220-1280 cm mode at both pH values. Potentials in this plot are referred to the normal hydrogen electrode. The wavenumbers for the band centers coincide at both pHs, giving a common slope of 112cm V. Other parameters, such as the halfwidths measured at the potential of maximum adsorption, are also similar (36.5 and 37.5 cm at pH 2.8 and 0.23, respectively). These properties, which are a... 

Figure 45. Coverage as a function of concentration for adsorption of cyclo-hexanol at zinc face curve 1, (0001), curve 2, (lOTO), and curve 3, (1120) at potential of maximum adsorption. " ...

For the (0001) face of zinc, a systematic change of the chain length of the adsorbate was analyzed. For n-propyl, n-butyl, and n-amyl alcohols (in 100 mM KCl + 0.1 mM H2SO4), the coverage varies with the concentration (at potential of maximum adsorption), as shown in Fig. 47. ... 

By comparing cyclic voltammetry with in-situ STM recorded simultaneously it seems that the cathodic current peak of bulk metal electrodeposition reflects the termination of metal deposition rather than a potential of maximum metal growth [11]. 

Since AE is small, the potential of maximum current lies close to En2. Also, given that A is negative in this experiment, we see that the peak anticipates E i2 by A /2. 

This maximum point is independent of nearly all experimental variables, for example, A ", Cq, and, most notably, A and co. The difference between Ey2 and the potential of maximum cot (f) provides access to the transfer coefficient a. 

Actual cot (f) data are shown in Figure 10.5.4 for TiCl4 in oxalic acid solution (25). The electrode reaction is the one-electron reduction of Ti(IV) to Ti(III). Note that the potential of maximum cot cf) is independent of frequency, as predicted above. 

One of the problems in electrocatalysis is that electrochemical reactions are generally carried out in aqueous or nonaqueous solution. Thus, the solvent may intervene in the over-all reaction. In addition, it is necessary to carry out the reaction under highly purified conditions. Otherwise, impurities in the solution may affect the kinetics of the reaction concerned, so that mechanism studies become difficult. For gas phase reactions, though impurity concentrations are generally lower than in electrochemical reactions, one uses high-vacuum techniques for purification. Electrochemical purification techniques— pre-electrolysis or adsorption of impurities near the potential of maximum adsorption—are often simpler. The activation of a poissoned catalyst is often difficult or impossible. An electrocatalyst can often be reactivated in situ, by pulse techniques (cf. Section VII,D). 

The adsorption is accompanied by a decrease in the differential capacity C in the region of E x, the potential of maximum in adsorption. At potentials more positive or more negative than Emwc the organic adsorbate is desorbed giving rise to typical adsorption-desorption peaks. 

Moreover, it is observed that the maximum of the three curves in Fig. 10 is located very close to om = 0. Therefore, the potential of maximum AS, AS and A5 di, is very close to the F pzfc. Close... 

V. WATER REORIENTATION ON SINGLE-CRYSTAL ELECTRODES FROM NANOSECOND LASER-PULSED EXPERIMENTS. POTENTIAL OF MAXIMUM ENTROPY OF DOUBLE-LAYER FORMATION... 

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