MECHANISM OF SURFACE-DIFFUSION OF GOLD ADATOMS IN CONTACT WITH AN ELECTROLYTIC SOLUTION

被引:115
作者
DONA, JM [1 ]
GONZALEZVELASCO, J [1 ]
机构
[1] UNIV AUTONOMA MADRID,FAC CIENCIAS,DEPT QUIM,E-28049 MADRID,SPAIN
关键词
D O I
10.1021/j100120a026
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Temperature, potential, and time-dependent measurements of the change of the roughness factor of electrodispersed gold electrodes allowed a derivation of the activation enthalpy and entropy values for the surface diffusion process of gold adatoms in contact with a 0.5 M H2SO4 aqueous solution. The measurements were carried out at five different potential values, negative and positive with respect to the zero charge potential of polycrystalline gold (E(z) = -0.41 V(MSE)) and a potential value within the potential range at which gold oxides are formed. The low preexponential factors deduced from In D vs T-1 plots give rise to negative values for the activation entropies, instead of the expected positive value for the same magnitude derived from measurements made at the gold-vacuum interface. The activation enthalpy values measured in the potential range between 0 and 1000 mV(SHE) decrease with the potential value, while the activation entropies increase with them, showing an example of the so-called compensation effect. These values are interpreted as the consequence of the formation of an activated complex for the surface diffusion process that is more ordered than the system: electrode surface + adatom original. The enhancement of order might be produced by the fact that before surface diffusion can take place, a partial charge transfer from the adatom to the electrode surface occurs which accumulates a positive charge on the adatom original, with the consequent orientating effect on the solvent dipoles forming part of the double layer.
引用
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页码:4714 / 4719
页数:6
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