SFG and DFG investigation of Au(111), Au(210), polycrystalline Au, Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing KCN and 4-cyanopyridine

Abstract

We report on potential-dependent in situ SFG and DFG spectroscopy carried out at Au(111), Au (210), polycrystalline Au, Au-Cu and Au-Ag-Cu electrodes in contact with aqueous solutions containing CN -and 4-cyanopyridine (4CP). Spectroelectrochemical work was complemented by cyclic voltammetry. The chief stress has been placed on systematising and quantifying the interaction between 4CP and CN -and the attending effects on the vibrational and electronic structures of the interface. The voltammetric behaviour of the investigated electrodes, modified by the addition of 4CP to the CN -electrolyte, denote changes in the CN -adsorption characteristics and effects of the adsorbed CN -layer on the electrodic reactivity of 4CP. The differences among the investigated electrodes can be explained in terms of their respective degrees of atomic packing or with alloying effects on the stability of adsorbed CN -. The potential-dependent spectra have been analysed quantitatively with a model for the second order non linear susceptibility accounting for vibrational and electronic effects. The spectral changes induced by addition of 4CP denote interaction of the aromatic with the electrode through the CN -monolayer. The non-resonant contribution yields information on the effects of 4CP on the fine structure of the bound electron density of states.

Observation of gold electrode surface response to the adsorption and oxidation of thiocyanate in acidic electrolyte with broadband sum-frequency generation spectroscopy

“…The NR contribution from gold is much larger than that from other metal electrodes (Ag, Co, Ni, Pt) due to the interband transition of Au lies in the visible range. Tadjeddine et al systematically modelled the metal surface contribution [26] (and references therein), and showed the difference between the phases of the NR contributions of SFG and DFG (difference frequency generation) spectroscopy of electrochemistry interfaces [26][27][28]. The electrode NR contribution is potential dependent and drastically depending on the nature of the electrode material.…”

An in situ IR-Vis Sum Frequency Generation Spectroscopy study of cyanide adsorption during zinc electrodeposition

“…We employed free CN¯-based aqueous electrolytes: a Zn(II)-cyanocomplex bath containing free CN¯ for the electrodeposition studies and a CN¯ solution for adsorption investigations on Au and Zn. The CN¯ solutions were obtained by dissolving 25 mM KCN and 0.1 M NaClO4 in milli-Q water or by prolonged cathodic reaction of 25 mM 4-cyanopyridine in the same perchlorate supporting electrolyte [17]. The cyanocomplex bath was obtained by dissolving 5 mM ZnO to the KCN solution, whereby the Zn(II) cyanocomplex forms spontaneously.…”