Single-crystal faces

It appears that no comprehensive review was published after Perkins and Andersen s work. Nevertheless, articles devoted to particular aspects have been written. Thus collections of data were compiled by Hamelin et al.24 for single-crystal face electrodes (Cu, Ag, Au, Sn, Pb, Zn, and Bi) in 1983, by Trasatti75,26 in 1986 and 1992, by Khrushcheva and Kazarinov27 in 1986, and by Lust et al.2 in 1996 for Bi, Sb, and Cd. 

While from a structural point of view metal/solution and metal/vac-uum interfaces are qualitatively comparable even if quantitatively dissimilar, in the presence of ionic adsorbates the comparability is more difficult and is possible only if specific conditions are met.33 This is sketched in Fig. 7. A UHV metal surface with ions adsorbed on it is electrically neutral because of a counter-charge on the metal phase. These conditions cannot be compared with the condition of a = 0 in an electrochemical cell, but with the conditions in which the adsorbed charge is balanced by an equal and opposite charge on the metal surface, i.e., the condition of zero diffuse-layer charge. This is a further complication in comparing electrochemical and UHV conditions and has been pointed out in the case of Br adsorption on Ag single-crystal faces.88... 

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Figure 9. Theoretical C,E curves (1, 2, 3) for single-crystal faces and (4) for a model polycrystalline surface calculated by the superposition of the C,E curves at E= const [Eq. (49)] with = 02 = = 1/3 1. (a) Faces with strong hydrophilicity and (b, c) faces with...

The idea in these papers67,223,224 was to identify the potential of the capacitance minimum in dilute electrolyte solutions with the actual value of Ea=o (i.e., <7ge0m( min) = Ofor the whole surface) and to obtain the value of R as the inverse slope of the Parsons-Zobel plot at min.72 Extrapolation of Cwom vs- to Cgg0m = 0 provides the inner-layer capacitance in the / C geom, and not C ea as assumed in several papers.67,68,223,224 In the absence of ion-specific adsorption and for ideally smooth surfaces, these plots are expected to be linear with unit slope. However, data for Hg and single-crystal face electrodes have shown that the test is somewhat more complicated.63,74,219,247-249 More specifically,247,248 PZ plots for Hg/... 

K. The electrical double-layer structure at Ag single-crystal faces has been studied extensively.6,10,i5,22,24,32,61,63,75,ss, 149-151,177a, 188,250-... 

The adsorption of aliphatic alcohols, which adsorb on metals with the hydrocarbon tail facing the electrode surface, shows different patterns on real Ag crystal faces440,441 with respect to quasi-perfect single-crystal face electrodes.442-444 This specific point will be discussed in detail in Section III. 

The value of Emin in the pseudo-stable state has been found to increase in the sequence (111) (100)aqueous solutions. It has been concluded that the Au-DMSO interactions vary much more with the atomic structure of the gold surface than the Au-H20 interactions and that the Au-DMSO interactions are stronger than forH20.477 Following Trasatti s relation,7 the values of A(<5 m - have been obtained for different planes of Au. It has been found that the difference (<5/M - S/s) for Au( 110) and Au( 111) planes is greater than 0.5 V.477 It should be noted that the same order of Au( 111) and Au(210) has been found in a 2.5 x 10-3 M KPF6 + AN solution.63,392,477... 

Over the past 10 years it has been demonstrated by a variety of in situ and ex situ techniques187,188 485 487 488 534 that flame-annealed Au faces are reconstructed in the same way as the surfaces of samples prepared in UHV,526-534 and that the reconstructed surfaces are stable even in contact with an aqueous solution if certain precautions are taken with respect to the potential applied and the electrolyte composition 485,487,488 A comprehensive review of reconstruction phenomena at single-crystal faces of various metals has been given by Kolb534 and Gao etal.511,513... 

Potentials of Zero Charge of Au Single-Crystal Faces in Aqueous... 

Eemo at 298 K and dE0 JdT for Au Single-Crystal Faces In 0.01 M HCIO4 Aqueous Solutions ... 

The R of electropolished Zn single-crystal face electrodes has been obtained from the shape of the adsorption-desorption peak of cyclohex-anol at various Zn and Hg surfaces.154 The roughness factor of Zn electrodes has been found to increase in the order Zn(0001) < Zn(lOlO) < Zn(llZO) with values in the range 1.1 to 1.25. 

Electrical Double-Layer Parameters of Bi Single-Crystal Faces in Various Solvents... 

The influence of the surface pretreatment of Bi single-crystal faces has been studied, and a noticeable dependence of Ea=0 on the surface structure has been established.152,133... 

The effect of the addition of various surface-active organic compounds (cyclohexanol, camphor) to an aqueous solution of Na2S04 in contact with Bi single-crystal faces has been studied by Raud etal 9 in using ellipsometry. SQ - was not specifically adsorbed, but at E> -0.5 V (SCE), slight oxidation of the Bi faces was possible. 

The C, values for Sb faces are noticeably lower than those for Bi. Just as for Bi, the closest-packed faces show the lowest values of C, [except Bi(lll) and Sb(lll)].28,152,153 This result is in good agreement with the theory428,429 based on the jellium model for the metal and the simple hard sphere model for the electrolyte solution. The adsorption of organic compounds at Sb and Bi single-crystal face electrodes28,152,726 shows that the surface activity of Bi(lll) and Sb(lll) is lower than for the other planes. Thus the anomalous position of Sb(lll) as well as Bi(lll) is probably caused by a more pronounced influence of the capacitance of the metal phase compared with other Sb and Bi faces28... 

Ni single-crystal faces in HzO + HCIO4 or H2SO4 solutions have been investigated by Arold and Tamm using impedance.743 Ni (100), (110), and (111) single-crystal faces were prepared by the method described by... 

Some measurements with Pt single-crystal faces have been published recently.140,210,773 Iwasita and Xia210 prepared platinum single crystals according to the method of Clavilier et a/.186 773 After flame annealing and cooling in an H2 + Ar mixture, the electrode was protected... 

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