Conductor proton/electronic

MIXED PROTON/ELECTRONIC CONDUCTORS 8.8.1 Proton Mixed Conductors... 

Platinum electrodes catalyze the breakdown of hydrogen into hydrogen nuclei [protons] and electrons. The electrons travel in a conductor, and the protons travel through the electrolyte, meeting at the other side, where platinum electrodes catalyze the combination of protons, electrons, and oxygen into water. 

The use of a mixed oxygen ion-electronic conductor membrane for oxygen separation with direct reforming of methane, followed by the use of a mixed protonic-electronic membrane conductor for hydrogen extraction has also been proposed in the literature [34]. The products are thus pure hydrogen and synthesis gas with reduced hydrogen content, the latter suitable, for example, in the Fish-er-Tropsch synthesis of methanol [34]. 

Proton-conducting materials [38-47], analogous to oxygen conductors but with stationary oxygen anions, can show mixed protonic-electronic conductivity, without considerable oxygen transport in hydrogen or water atmospheres [40,41], These materials have not been widely studied in comparison... 

Reduction of a,fi-unsaturated ketonesThis highly hindered borane accepts an electron from sodium metal to give a blue solution of the radical anion which can serve as a conductor of electrons for reduction of a,/3-unsaturated ketones. Thus A1,9-octalone-2 (1) is reduced by TMB, sodium, and a proton source (t-butanol) in anhydrous 1,2-dimethoxyethane (nitrogen) in high yield (85-95%) to a mixture of / j-2-decalone (70%) and cw-2-decalone (30%), the equilibration point for this reduction. Overreduction to the alcohol is negligible. If the reduction... 

In the proton-electron conductors, charged carriers are protons (OH ), vacancies (Vq), electrons (e ), and electron holes (h ). The concentrations of the defect species in a typical proton conductor can be described by the following stoichiometric equation [22] ... 

Li L, Iglesia E. Modeling and analysis of hydrogen permeation in mixed proton-electronic conductors. Chem Eng Sd. 2003 58 1977-88. 

Figure 1.1a shows schematically the operation of a membrane that is permeable to hydrogen molecules (corresponding to a porous membrane or a dense material in which molecules dissolve and diffuse) or to neutral hydrogen atoms (corresponding to a material in which hydrogen dissolves dissociatively, as in a metal). Figure 1.1b shows schematically how a mixed proton-electron conductor performs the same process by so-caUed ambipolar diffusion of both protons and electrons in the same direction to maintain electroneutrality and zero net current. 

Surface Kinetics of Hydrogen Permeation in Mixed Proton-Electron Conductors 21... 

Tab. 2.2 S ummary of transport numbers of various mixed protonic-electronic conductors in various gas concentration cells. 

Intercalated or surface adsorbed species in the electron conductor. Protons and li ions, if present in the hole conductor, may be capable of intercalating into the oxide film, affecting both the potential energy for electron stabilization and the ease of electronic conduction. Surface absorbed cations influence electronic states near the surface. Adsorption of OH groups influences electronic states and proton transport. Water molecules, which are expected to be present around the oxide surface even in dry solvent, may be dissociatively adsorbed leaving adsorbed OH species and mobile protons, which influence electronic states and conductivity. 

Fig. 37.1. Principle of an all solid battery with a protonic conductor as electrolyte and two mixed protonic-electronic conductors as electrodes.

Zuo, CJ5., Dorris, S.E., Balachandran, U., and Liu, M.L (2006) Effect of Zr-doping on the chemical stability and hydrogen permeation of the Ni-BaCeo.8Yo.203 a mixed protonic-electronic conductor. Chem. Mater., 18,4647-4650. 

A novel method for improving the conductivity of DNA involves close association or even incorporation of divalent metal ions such as Zn, Ni, and Co into the hehx at pH>8.5 to form metallated DNA (M-DNA). Other divalent metals such as Mg + and Ca " do not form M-DNA. In photophysical studies using ds-DNA where one strand is labeled with a fluorescein fluorophore and the complementary strand carries a rhodamine quencher, the fluorescein fluorescence is quenched only under conditions where M-DNA forms. M-DNA is an efficient conductor of electrons over distances as long as 500 basepairs and possibly as long as several micrometers. It was proposed that in M-DNA the Zn cations replace the imino protons of every thymine and guanine in addition to saturating the backbone phosphates as do other cations such as Mg (Scheme 6). Importantly, M-DNA... 

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