Single-crystal surfaces cyclic-voltammetry

Hamelin A. 1996. Cyclic voltammetry at gold single-crystal surfaces. Part 1. Behaviour at low-index faces. J Electroanal Chem 407 1-11. 

Figure 2A. Cyclic voltammetry for the single crystal surfaces laying on the 111 zone line. Sweep rate 50 mV/s.

Tlie low index svirfaces of platinum single crystals were examined with cyclic voltammetry. As mentioned in Chapter 2, single crystal surfaces are reconstructed by Pt-OH formation and reduction at a higher potential. Therefore, it was impossible to clean the surface thoroughly by potential steps without disturbing the surface structure. 

This result is consistent with the observed effective poisoning of the CO oxidation reaction as reflected in the increased potential induced by bismuth in the cyclic voltammetry on the supported platinum electrodes (Figure 10a). The voltammetry of CO stripping on the supported catalysts indicates a similar behavior to that found on Pt(llO) in that bismuth results in a higher overpotential for CO oxidation. One must conclude that the morphology of the supported platinum catalyst results in facets more akin to the more open-packed Pt(l 10) surface than the Pt(lll) surface, a conclusion supported by comparison of the bismuth redox chemistry on the supported catalyst and the single-crystal surfaces [77]. 

One of the main uses of these wet cells is to investigate surface electrochemistry [94, 95]. In these experiments, a single-crystal surface is prepared by UHV techniques and then transferred into an electrochemical cell. An electrochemical reaction is then run and characterized using cyclic voltammetry, with the sample itself being one of the electrodes. In order to be sure that the electrochemical measurements all involved the same crystal face, for some experiments a single-crystal cube was actually oriented and polished on all six sides Following surface modification by electrochemistry, the sample is returned to UHV for... 

The surface electrochemistry of Pt single-crystal electrodes has been exhaustively studied using cyclic voltammetry.100 186 188 197 209 412 753-756,771,-773,779-788,794-796 qq g technique has been proved to be highly... 

Activation (of noble metal electrodes) — Noble metal electrodes never work well without appropriate pretreatment. Polycrystalline electrodes are polished with diamond or alumina particles of size from 10 pm to a fraction of 1 pm to obtain the mirror-like surface. The suspensions of polishing microparticles are available in aqueous and oil media. The medium employed determines the final hydrophobicity of the electrode. The mechanical treatment is often followed by electrochemical cleaning. There is no common electrochemical procedure and hundreds of papers on the electrochemical activation of -> gold and platinum (- electrode materials) aimed at a particular problem have been published in the literature. Most often, -> cyclic and - square-wave voltammetry and a sequence of potential - pulses are used. For platinum electrodes, it is important that during this prepolarization step the electrode is covered consecutively by a layer of platinum oxide and a layer of adsorbed hydrogen. In the work with single-crystal (- monocrystal) electrodes the preliminary polishing of the surface can not be done. 

---