Migration of protons

Some investigators have reported the isotope effect of migration by replacing protons with deuterons . Scherban et al. observed non-classical behaviour in Yb-doped SrCeOs the ratio of conductivity o-h/ 7d is about 2.5 which is significantly greater than the classical value of /l, although the reason for this is not yet clear. 

Using the values of proton concentration [H] calculated as above, the mobility of protons can be evaluated from the Einstein equation  

Fukatsu et al. have also estimated the mobility in SrCeo.gsYbo.osOj-, by means of a polarization method, and the values were close to those obtained from the thermal desorption method and Eqn (8.12) . 

Chandra, Proton Conductors in Superionic Solids and Solid Electrolytes, S. Chandra et al. (eds) (Academic Press (1989)) 185-226. 

Poulsen, Proton Conduction in Solids in High Conductivity Solid Ionic Conductors T. Takahashi (ed) (World Scientific (1989)) 166-200. 

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Annular prototropy in pyrans involves migration of protons between different sites in the ring. The equilibrium situation is depicted in equation (6). The systems in which this... 

Under these conditions the main mechanism describing the transfer of OH groups corresponds to condensation via disordered migration of protons on the surface (a process of the activated diffusion of OH groups). At the final stage, water is evolved, owing to the interaction of two OH groups that accidentally approach each other to a... 

From Table 5 and Table 6 it can be seen that all the samples of different calcination time and aging time possess nearly the same acidity at a particular calcination temperature, revealing the negligible effect of the calcination time and aging time on the surface total acidity. However, Table 7 shows that the total number of acid sites and the number of the BrOnsted acid sites on the catalysts decrease with an increase in calcination temperature. It is known that the surface acid sites of hydroxyl-Zr bentonite mainly stem from surface hydroxyl and exposed metal cation [6], and the Bronsted acid sites result from protons on the surface of the octahedral layers. When the calcination temperature increases, the migration of protons to the octahedral layers of montmorillonite will become easier, leading to the decrease of the number of BrGnsted acid sites. 

J. Turkevich The slide was from an earlier published work presented at the Amsterdam International Congress on Catalysis. It indicates first that the catalytic activity per site is not constant as one increases the number of sites, but more dramatically that it increases with increases in site number even when these new sites are not available to the substrate (cumene) or poison quinoline. This we interpret to be owing to interaction and migration of protons (and/or electrons) among the various sites. 

An appropriate model of CCL operation should account for the interdiffusion of oxygen, nitrogen, and water vapor, migration of protons and electrons, and kinetics of the electrochemical reaction. The pertinent theory was developed in Refs. 8, 9, 15. A model similar to that was more recently studied analytically [17, 107, 108], and we will dwell on these transparent closed form results. We will see that having such solutions at hand helps in revealing the reserves for optimization of the structure and function of the catalyst layers. 

The basic feature derived by the model of Stuchebrukchov, that transient protonation of surface groups accelerated the migration of protons on the surface has been confirmed in real time measurements carried out by Nachliel and Gutman [17]. Figure 20.1 depicts time-resolved measurements of the protonation of the in-... 

The fundamental reaction in the hydrolysis of metal alkoxides is a nucleophilic substitution (Sn ) that involves a nucleophilic addition of OH group onto the electrophilic metal center (M ). As a result, the coordination number (CN) of the metal atom is increased in the transition state, which leads to the migration of proton toward an alkoxy group, consequently knocking off the protonated ROH ligand (Figure 12). The chemical reactivity of metal alkoxides toward nucleophilic reactions mainly depends on the strength of the nucleophile, the electrophilic character of the metal atom, and its ability to increase the CN. 

One elementary reaction which features in all of the mechanisms outlined above, is the migration of protons between sulfur and metal atoms as shown in Equation (2). 

Liu JF, Nowick AS. The incorporation and migration of protons in nd-doped BaCeOs. Solid... 

Tab. 2 Data for net reactions (spaces) and partial reactions (lines) described in the text, ne = number of involved electrons mH+ = number of involved protons. The total cathodic reduction is described for an island mechanism differing from anodic formation. Partial current densities give the local current dependent on the coordinate x. Transference numbers t have to be considered within the oxide, for example, in case of oxide formation i = /i5 = /i6 + (17 = (f+ + t )i = i i4. In case of partial oxidation/reduction of an oxide by a combined ITR/ETR the local current densities of and have to be added i(x) = / is = ii7(x) + inM = ( e(x) + t-(x))/ = /14. Cathodic intercalation of protons takes place by a process analogue to anodic partial oxidation, differing only by the sign of / and the migration of protons instead of -ions...

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