Current-voltage characteristics thermodynamic

Ihe actual from the thermodynamic electrode potential. The polarization is Ihe result of the irreversibility of the electrode process, that is, the activation polarization and the voltage loss, which develops from concentration gradients nf the reactants. This leads to the current-voltage characteristics as shown in Fig. 2,... 

The thermodynamic treatment of electrochemical processes presented in Sec. 2.2 describes the equilibrium condition of a system but does not present information on nonequilibrium conditions such as current flow resulting from electrode polarization (overvoltage) imposed to effect electrochemical reactions. Experimental determination of the current-voltage characteristics of many electrochemical systems has shown that there is an exponential relation between current and applied voltage. The generalized expression describing this relationship is called the Tafel equation. 

The most characteristic parameter of a compound, when examined polarographically by d.m.e. or r.d.e. is the half-wave potential. It is a potential measured in the half height of the wave on the current-voltage curve. In the case of a thermodynamically reversible redox process, the half-wave potential virtually corresponds to the redox potential of the... 

At the effective property or continuum level, the simulation of electrode and cell performance basically requires only a parameterised electrochemical model. Such an electrochemical model is usually described as a current-voltage relation, or I-V curve, for a single cell, in terms of parameters that are effective cell properties and operational parameters. The I-V relation describes the voltage (potential) loss at a specified current with respect to the ideal thermodynamic performance, which is called overpotential or polarisation (q). This cell I-V curve is specific for the materials, structural characteristics, and operational parameters (gas compositions, pressure, temperature) of a given PEN element. 

PEM fuel cell characteristics are generally described with polarization curves. The thermodynamic equilibrium potential of the hydrogen/oxygen reaction is reduced by various overvoltage terms that depend on mass transport, kinetic, and ohmic phenomena within cell. In other words, the output voltage of a single cell is attributable to different current, temperature, and pressure dependant factors [1]. 

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