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Table 4.1. Analogy between the kinetics of a fuel cell and that of a catalytic reactor
where
i = P exp{fl
i = Current density (C/s/area) = kinetic parameter
jg =
where 4
= Exchange or spec current
density (A/area= C/s/area)
‘ = Reference oxygen pressure (atm)
e = Effectiveness factor (dimensionless) = Oxygen partial pressure in the fuel cell
(atm)
= aF/RT = 1/Tafel slope where a = Transfer coefficient =kinetic
parameter
F = Faraday ‘s constant (C/mo!)
R = Ideal gas constant (J/mol/K)
T = Temperature (K)
A V = Voltage difference needed to drive the reaction (J9 = Vihermo — Vcat
where Vthermo = Thermodynamic voltage (V) V = Cell voltage at catalyst
surface (T’7 = V +
AV
where V = Voltage measured at fuel cell terminals
A V Voltage difference between external point and catalyst surface = iRa where R is the
resistance (ohm-cm between the two points
*
b
I E’
Rate =k exp1— cat
where
Rate* = Reaction rate (mol O2/mcatalys/s) I = Spec rate (mol O2/mcatalys/s/atm
02) = kinetic parameter
e = Effectiveness factor
= Oxygen partial pressure in the reactor (atm)
E* =E/R(K)
where E = Activation energy (J/mol) = kinetic parameter
R = Ideal gas constant (J/mol/K)
Tcat = Temperature at the catalyst surface
= Texjernai + AT
where AT = Temperature dtfference between external surface and catalyst surface
Fuel Cells
(Electrochemical Systems)
Catalytic Reactors
(Chemical Systems)
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