Anodic oxidation stoichiometric coefficient

Reactions (3.9) to (3.11) proceed rapidly to equilibrium in most anodic solid oxide fuel cell (SOFC) environments and thus H2 (Eq. 3.8) rather than CH4 is oxidized electrochemically resulting in low polarization losses. Upon doubling the stoichiometric coefficients of equation (3.8), summing equations (3.8) to (3.11) and dividing the resulting coefficients by two one obtains ... 

The governing equations - that is, mainly the component and the total mass balances in the anode channels - are provided here in dimensionless form. The five ordinary differential equations (ODE) with respect to the spatial coordinate describe the development of the five unknowns in one single anode channel, namely the mole fractions, with i = CH4, H2O, H2, CO2, as well as the molar flow density inside the anode channel, y. Here, the Damkohler numbers, Da/, are the dimensionless reaction rate constant of the reforming and the oxidation reaction, respectively, the rj are the corresponding dimensionless reaction rates, and the v, j are the stoichiometric coefficients ... 

The second item that needs to be fixed is the number of species and the reactions, including the stoichiometric coefficients and also the kinetics of the processes. In this context, in electrochemical oxidation processes it is important to discern between two types of anodes those that behaves only as electrons sinks (named nonactive) and those that suffer changes during the electrochemical oxidation which influence on the treatment (named active electrodes). In both cases, the main processes related to removal of the pollutant that involves irreversible oxidative routes. Consequently, the reductive processes are less important and it can be presumed that in the cathodic zone only hydrogen evolution occurs. Nevertheless, if some organic compound can be reduced at the cathode, the mass-transfer and the reduction processes must be included in the model scheme. 

The sign of the current density follows the sign of the stoichiometric coefficient. If Vg is plus, electrons appear on the product side, and the reaction is an oxidation. The current is an anodic current and has a positive sign. The symbol for an anodic current density is i+ or. If is minus, electrons appear on the reactant side, and the reaction is a reduction. The current is a cathodic current and has a negative sign. The symbol for a cathodic current density is i or i. ... 

Stoichiometric coefficient of the anodic oxide layer as a function of oxidation potential lead electrode in H2SO4 solution [116],... 

The stoichiometric coefficient of the oxide in the corrosion layer has been determined by conventional analysis to ascertain whether low valency oxides are formed at high potentials [116]. Figure 2.42 shows that, despite the high positive potential, the stoichiometric coefficient of the oxide layer does not reach values higher than 1.75. This is an integral value of the stoichiometric coefficient and refers to all oxides formed throughout the anodic layer, from the metal surface to the interface corrosion layer solution. The lead oxidation process sustains this... 

Electrochemical reactions are heterogeneous reactions characterized by at least one electron charge-transfer step. The electron e appears thus in the reaction equation with its stoichiometric coefficient n. The anodic oxidation of a reagent A to form the product B can be written as... 

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