Polycrystalline electrode activated

Anion adsorption and charge transfer on single-crystal electrodes—Continued experimental procedure, 157-159 polycrystalline electrode activated by electrochemical cycling, 165,167 Pt(531) electrode, 167,168/ state of electrode surface using cyclic voltammetry, 164,165/ voltammetric profile, 158/, 160 Antigen-antibodies, use in glass surfaces, 202-209... 

AE = 0. In the overpotential region, where the final coverage should be independent of E, the overlayer is formed faster as the overpotential increases. The result suggests that activation energy is supplied by the overpotential. Similar results were reported in related SHG measurements of the UPD kinetics of thallium deposition on polycrystalline electrodes within the overpotential region [54]. 

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. 

Pt particles supported on high surface-area carbon substrates to form supported catalyst (abbreviated as Pt/C) is the most widely used ORR catalyst at the current state of technology. The surface characteristics of Pt particles supported on carbon are similar to that of Pt polycrystalline electrode surface, which can be observed by their surface CVs. However, the ORR activity of Pt/C is different from what can be observed for polycrystalline Pt surface. This difference is possibly due to some differences in the superficial structure, or a too strong adsorption of oxygenated species on very small particles. In addition, the ORR activity of carbon-supported Pt particles might also be affected by the electronic properties of Pt atoms from carbon. 

Aaronson, B. D. Chen, C.-H. Li, H. Koper, M. T. Lai, S. C. Unwin, P R., Pseudo-single-crystal electrochemistry on polycrystalline electrodes Visualizing activity at grains and grain boundaries on platinum for the Fe2-H /Fe3H- redox reaction. Journal of the American Chemical Society 2013,135, 3873-3880. 

In their pioneering work on the formation of photoelectrochemically active metal sulfides by oxidation of the parent metal electrode. Miller and Heller [29] reported the anodic formation of polycrystalline Bi2S3 on a bismuth metal electrode in a sodium polysulfide cell, wherein this electrode was used in situ as photoanode. When a Bi metal electrode is anodized in aqueous sulfide solutions a surface film is formed by the reaction... 

In Chapter 2, the electrochemical oxidation of carbon monoxide, which is considered as the key intermediate for methanol oxidation, is investigated using electrochemical and spectroscopic methods for polycrystalline and single crystal platiniim electrodes. In Chapter 3, the electrochemical oxidation of methanol on the same electrodes was treated. In Chapter 4, electrocatalytic activities of platinum modified by adding secondary elements will be disciissed. 

In the case of alloys [593, 594], the amorphous alloy of Fe60Co2oB10Silo has been identified as among the most active electrocatalysts, with an activity comparable to polycrystalline Pt. However, the Tafel slope is always close to or higher than 120 mV, and it normally increases with temperature [593] so that the latter has no activating effect on the state of the surface. It has been proposed [594] that the application of amorphous alloys to both electrodes in a water electrolyzer can reduce the expenditure of electrical energy by about 6%. However, the polycrystalline Pt taken as a reference for these studies showed [593] b - 140 mV and jo 10-4 A cm-2. At 1 A cm-2 this polycristalline Pt exhibits an overpotential of 560 mV. If we compare this activity with that claimed [5, 519], for instance, for thermal Ni-Mo alloys, the expectations for amorphous phases cannot be great. 

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