Spectroscopy of Metal/Electrolyte Interfaces

It is still a long way to reach the same holistic understanding of properties and processes at metal/ electrolyte interfaces as has been reached for surfaces in ultrahigh vacuum (UHV). In order to over-come this backlog i) more surface physisists should venture to "interfacial electrochemistry", because ii) new analytical techniques need to developed which replace all particle beam based methods which work successfully only in vacuum.

In this lecture I will present and discuss investigations of several electrochemical interface pheno-mena as they occur in electro-catalysis, anion-adsorption, metal-deposition, molecular self-assembly, structural phase transitions, etc., using a number of in-situ methods like various modes of optical spectroscopy (IRRAS, RAS, etc.), X-ray diffraction (XRD) and scanning tunneling microscopy/ spectros-copy (STM/STS) as well as (still unavoidably) ex-situ methods like electron spectroscopies (XPS; AES), low energy electron diffraction (LEED) and ion scattering spectroscopy (ISS). As an example Fig.1 shows EC-STM images and IRRAS spectra of a) the "stripe-structure" and b) the "cavitand-structure" of dibenzyl-viologen molecules adsorbed on Cu(100) in HCl-solution. XPS proves the monocationic [dicationic] state of the molecular building blocks in a) [b)], while IRRAS enables a structural refine-ment of the orientation of the individual molecular cations in the respective structure (see models).

References

[1] T.-D. Pham, K. Wandelt, P. Broekmann, Chem. Phys. Chem. 8 (16) (2007) 2318-2320

[2] M.Röefzaad, PhD-thesis, Univ. Bonn, Germany; and M.Röefzaad, K.Wandelt, in preparation

Fig. 1 EC-STM images and IRRAS spectra of a) the "stripe-structure" and b) the "cavitand-structure" of dibenzyl-viologen adsorbed on Cu(100) in HCl-solution (see text)