Copper electrodes, Raman enhancement

Thierry D., Leygraf C., The influence of photoalteration on surface-enhanced Raman-scattering from copper electrodes, Surf. Sci. 1985 149 592-600. 

Liang, E. J., Yang, Y., and Kiefer, W. (1999). Surface-enhanced Raman spectra of fulvic and humic acids adsorbed on copper electrodes. Spectrosc. Lett. 32, 689-701. 

Rubim J, Gutz IGR, Sala O, Orville-Thomas WJ. Surface enhanced Raman spectra of benzotriazole adsorbed on a copper electrode. J Mol Struct 1983 100 571. 

V vs. SHE by surface enhanced Raman spectroscopy, and on a Cu deposited Pt electrode by infrared absorption spectroscopy.2° These facts established tliat CO is intermediately formed at a copper electrode during CO2 reduction and further reduced to hydrocarbons and alcohols. 

Raman scattering gives information about molecular or sohd-state vibrations. In the presence of some electrode materials (e.g. silver or copper) a considerably enhanced sensitivity for molecules adsorbed at the electrode surface in the form of a monolayer can be achieved. This surface-enhanced Raman scattering effect can be transferred to other electrode materials coated in the form of a very thin layer onto a silver or copper substrate [32]. The recently developed TERS technique (Tip-Enhanced Raman Spectroscopy [33]) provides additional and highly resolved mapping information. 

Investigation of electrode solution interfaces by in situ vibrational spectroscopy has two principal advantages firstly the species present and their structures are directly characterized by their spectra and, secondly, these spectra are sensitive to the environment and therefore can be used to probe complex interactions. Raman spectroscopy is particularly well suited to the investigation of aqueous systems and in certain cases the adsorption of neutral species, of anions in the double layer and of the solvent (as well as interactions between these species) can now be characterized[48]. Vibrational spectroscopy of systems of practical importance is illustrated by the Surface Enhanced Raman Spectra (SERS) of the corrosion inhibitor thiourea adsorbed at silver and copper electrodes[49] it should be noted that inhibitors such as thiourea are also used as plating additives. 

Costa, L.A.E., Breyer, H.S. and Rubim, J.C. (2010) Surface-enhanced Raman scattering (SERS) on copper electrodes in l-n-butyl-3-methyhmidazolium tetrafluorborate (BMI.BF4) The adsorption of benzolriazole (BTAH). Vibrational Spectroscopy, 54,103-106. 

Chemical origins of surface-enhanced Raman scattering by cyanide on copper electrodes. /. Chem. Soc., Faraday Trans. 1, 81 (9), 2123-2130. 

Niaura, G. and Malinauskas, A. (1993) Surface-enhanced Raman scattering from chloride on copper electrodes. Chem. Phys. Lett., 207 (4), 455—460. 

Niaura, G. (2000) Surface-enhanced Raman spectroscopic observation of two kinds of adsorbed OH ions at copper electrode. Electrochim. Acta, 45 (21), 3507-3519. 

Fortunately, in favorable cases enhancement mechanisms operate which increase the signal from the interface by a factor of 105 — 106, so that spectra of good quality can be observed - hence the name surface-enhanced Raman spectroscopy (SERS). However, these mechanisms seem to operate only on metals with broad free-electron-like bands, in particular on the sp metals copper, silver and gold. Furthermore, the electrodes must be roughened on a microscopic scale. These conditions severely limit the applicability of Raman spectroscopy to electrochemical interfaces. Nevertheless, SERS is a fascinating phenomenon, and though not universally applicable, it can yield valuable information on many interesting systems, and its usefulness is expected to increase as instrumentation and preparation techniques improve. 

Recent surface enhanced Raman scattering (SERS) measurements, carried out during the reduction of CO2 on the Cu surface [29], provide some insight into a series of events associated with deactivation of the electrode. These include (i) the time-dependent decay of the SERS bands corresponding to adsorbed CO paralleled by (ii) the increase of a new band attributed to the formation of a "patina" like species (including copper oxide, hydroxide and carbonate). At this stage, the latter surface compound appears as the most likely poisoning species. 

SM Angel, LF Katz, DD Archibald, LT Lin, DE Honigs. Near-infrared surface-enhanced Raman spectroscopy. 1. Copper and gold electrodes. Appl Spectrosc 42 1327-1331, 1988. 

---