Potential induced reconstruction

Besides surface reconstructions induced by heat treatment, potential-induced reconstruction has recently become a topic of interest in electrochemistry. It has been observed that at potentials negative with respect to the potential of zero surface charge, [Kolb, 1996, 2002 Dakkouri, 1997], the reconstructions found under UHV conditions are also stable in contact with an electrolyte. Although aU low index faces of Au and Pt undergo potential-induced reconstruction, it has been particularly well characterized for Au(lOO) (Fig. 5.5). 

In the first study of its kind, second harmonic generation has been used to study potential induced reconstruction on Au(lll) and Au(100) by Kolb and coworkers [156]. These surfaces have been known to reconstruct in UHY when they are clean [153, 157], Surface reconstruction occurs when the surface atoms of a solid rearrange themselves in a structure different from that expected from simple termination of the bulk lattice. Various studies by cyclic voltammetry, electroreflectance spectroscopy and ex situ electron diffraction have suggested that flame-treated crystals form stable reconstructions in solution. Unfortunately, due to the lack of in situ probes, very little direct evidence for this reconstruction has been available. 

Fig. 3 Cyclic voltammogram for Au(lll) in 0.05 M H2SO4, scan rate 10mVs In-situ STM-images represent the substrate surface structure at various stages of the potentio-dynamic experiment A large-scale image of a thermally reconstructed Au(lll)-(px.y/3) surface, E = - 0.20 V B atomic resolution of A C Au(lll)-(1 x 1) surface with monatomic high gold islands after lifting the surface reconstruction, E = 0.60 V D atomic resolution of C E disorder/order transition of the ( 3 x 7) (hydrogen) sulfate overlayer F potential-induced reconstructed Au(lll)-(px.y/3) surface at = - 0.20 V...

Flame-annealed Au single crystals were more frequently used for various studies including the potential induced reconstruction investigated by several groups [6, 7, 17]. However, it must be emphasized that the flame-anneaUng method can be applied only to Au, Pt, Rh, Pd, Ir, and possibly Ag. 

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