Interface compound-electrolyte

Thus in Figure 19 lattice vacancy with a trapped hole is injected at the compound electrolyte interface, the imperfection at the metal-compound interface reacts to release a vacancy into the metal. Alternatively, in Figure 20 the exchange process injects a lattice vacancy on the cation lattice which appears at the metal compound interphase to release an electron and transfer a metal ion into the surface region. 

Figure 20. Model boundary interphase exchange currents involving lattice vacancy injection at the compound-electrolyte interface and vacancy exchange into the metal releasing an electron and transferring a metal ion into the compound layer (12)...

Adsorption of various organic compounds (e.g., cyclohexanol, adamantanol-1, and camphor) has been studied at a renewed Sn + Pb alloy/electrolyte interface.820-824 The time variation of the surface composition depends on the solution composition, the nature and concentration of the surface-active substance, and on E. The " of cyclohexanol for just-renewed Sn + Pb alloys shifts toward more negative E with time, i.e., as the amount of Pb at the Sn + Pb alloy surface increases. 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

Most earlier papers dealt with the mercury electrode because of its unique and convenient features, such as surface cleanness, smoothness, isotropic surface properties, and wide range of ideal polarizability. These properties are gener y uncharacteristic of solid metal electrodes, so the results of the sohd met electrolyte interface studies are not as explicit as they are for mercury and are often more controversial. This has been shown by Bockris and Jeng, who studied adsorption of 19 different organic compounds on polycrystaUine platinum electrodes in 0.0 IM HCl solution using a radiotracer method, eUipsometry, and Fourier Transform Infrared Spectroscopy. The authors have determined and discussed adsorption isotherms and the kinetics of adsorption of the studied compounds. Their results were later critically reviewed by Wieckowski. ... 

Beyond any doubt, the electrode/electrolyte interfaces constitute the foundations for the state-of-the-art lithium ion chemistry and naturally have become the most active research topic during the past decade. However, the characterization of the key attributes of the corresponding surface chemistries proved rather difficult, and significant controversy has been generated. The elusive nature of these interfaces is believed to arise from the sensitivity of the major chemical compounds that originated from the decomposition of electrolyte components. 

In this paper our results to simulate the photoactive semiconductor/ electrolyte interface in UHV by adsorbing halogens and H20 on semiconductor surfaces are described. For these experiments layer type compounds and ternary chalcogenides have been considered because clean faces can easily be prepared by cleaving the crystals in UHV and because the reactions with halogens are intensively studied for photoelectrochemical solar cells. 

Table 3, which presents the various surface compounds formed on Li electrodes in the various solutions, together with reaction schemes 1-10, describes well the basic surface chemistry developed on the carbons. Similar results concerning the surface chemistry developed on carbons in alkyl carbonate mixtures have also been obtained by others [363-365], Hence, carbon electrodes are also solid electrolyte interface (SEI) electrodes, similar to lithium i.e., the overall insertion process of Li into the carbons requires the necessary step of Li ion... 

Surface-active substances — are electroactive or elec-troinactive substances capable to concentrate at the interfacial region between two phases. Surface-active substances accumulate at the electrode-electrolyte - interface due to -> adsorption on the electrode surface (see -> electrode surface area) or due to other sorts of chemical interactions with the electrode material (see - chemisorption) [i]. Surface-active substances capable to accumulate at the interface between two immiscible electrolyte solutions are frequently termed surfactants. Their surface activity derives from the amphiphilic structure (see amphiphilic compounds) of their molecules possessing hydrophilic and lipophilic moieties [ii]. 

Also contained in the compilation in Table 5 are some early studies oriented toward the mechanistic aspects of the photoelectrochemical oxidation of water (and other compounds) at the n TiCh electrolyte interface, as exemplified by Entries 23 and 29 (Refs. 243 and 249 respectively). More recent and representative studies of this genre include Refs. 258-289. 

The last decade has seen an explosion of activity in the field as electrochemists have wrestled with unfamiliar, and often intractable, problems generated by the very wide range of materials investigated, difficulties often compounded by the use of polycrystalline samples whose bulk and surface properties have proved resistant to control. In addition to the elemental semiconductors and the III/V materials, a huge range of n- and p-type oxides, sulphides, selenides, and tellurides have been described and surface and bulk modifications carried out in the hope of enhancing photoelectrochemical efficiency. New theoretical and experimental tools have developed apace and our fundamental understanding of the semiconductor-electrolyte interface has deepened substantially. 

Becquerel Photovoltaic Effect in Binary Compounds. Appears to be the first study on die mechanism of the photovoltaic effect on a CdS/electrolyte interface. 486... 

After the absorption of a photon sufficiently close to the semiconductor/ electrolyte interface, primary separation of the electron and hole will occur. The minority carrier (hole) may diffuse to the inner edge of the depletion layer, and migrate through the depletion layer towards the surface. Diffusion occurs in a time equal to the life time of the minority carrier in the bulk, t, which for compound semiconductors is often in the microsecond or nanosecond range (in very pure Si, the minority carrier life time is much larger (ms) [158]). In section 2.2, it was shown that... 

One needs to know optical constants to calculate IRRAS spectra of molecules either adsorbed at the electrode surface or resident inside the thin-layer cavity. The isotropic optical constants of a given compound are usually determined from transmittance spectra. A pressed peUet, prepared by grinding the dispersion of the compound with a KBr or KCl powder, is typically used as a sample. Recently, Arnold et al. [41] have demonstrated that this method can yield non-reproducible results due to different histories of the sample preparation. In addition, the optical constants determined using the powder method can be quite different from those of the film at the metal/electrolyte interface because of the difference in the environment. 

The reactive semiconductor-electrolyte interface makes stability a major issue in photoelectrochemical solar energy conversion devices, and aspects of thermodynamic and kinetic stability are briefly reviewed here. Thermodynamic stability considerations are based on so-called decomposition levels [56, 57] that are determined by combining the decomposition reaction with the redox reaction of the reversible hydrogen reference electrode. The anodic and cathodic decomposition reactions of a compound semiconductor MX can be written for aqueous solutions as... 

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