Abstract
The concentration and potential gradients across an electrolyte-containing membrane of the hydrogen-oxygen fuel cell have been calculated taking into account the following processes: diffusion of all solution components, ion migration in the electric field, permeation flux of the solution, external water vapour flows, water vapour transport in gas bubbles. A theory of the self-regulation of water removal has been developed, which takes account of the mass exchange conditions in the membrane and in the whole fuel cell, as well as the concepts of the buffer capacity of a fuel cell with a capillary membrane. The self-regulation of water removal during changes of the current or during changes of parameters influencing the rate of water removal, as well as the self-regulation in the case of a non-uniform process distribution over the electrode surface have been considered.
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Abbreviations
- c :
-
concentration of KOH in solution
- c 0 :
-
mean KOH concentration in the membrane
- \(c_{H_2 O}\) :
-
water concentration in the KOH solution
- D :
-
diffusion coefficient
- F :
-
Faraday constant
- i :
-
current density
- i 1,i cr :
-
limiting current densities due to a drop ofc at the anode to zero or to a beginning of KOH crystalization at the cathode.
- J:
-
external water vapour flux from the electrode
- j:
-
flux of ions or water molecules in the cell from anode to cathode
- k :
-
water transfer coefficient (Equation 4)
- p :
-
water vapour concentration at the electrode surface
- ¯p :
-
water vapour concentration at the surface of the condenser (evaporator)
- Q :
-
buffer capacity of the cell (Equation 6)
- R :
-
gas constant
- ¯T :
-
temperature at the electrode surface
- T :
-
temperature at the surface of the condenser (evaporator)
- t :
-
ion transfer number
- u :
-
ion mobility
- V :
-
solution volume in the cell (for unit electrode area)
- v :
-
permeation speed of the solution
- v * :
-
value ofv for a cell withα=0
- x :
-
relative electrolyte content (Equation 7)
- y :
-
coordinate perpendicular to membrane surface
- α :
-
stoichiometric coefficient of water transfer (Equation 8)
- β :
-
proportionality factor defined by Equation (18)
- γ :
-
proportionality factor between Δp and -Δc
- δ :
-
membrane thickness
- ε:
-
factor of transfer decrease in the membrane
- τx, τΔC :
-
characteristic time of establishment of the balance solution content in the cell and the concentration gradient in the membrane
- ψ :
-
electrostatic potential in the solution
- Δψohm :
-
ohmic potential difference
- Δψdiff :
-
diffusion potential difference
- A:
-
anode
- C:
-
cathode
- +:
-
cation
- −:
-
anion
- 0:
-
ref. tox=0
- 1:
-
ref. tox = 1
- g:
-
gas phase
- 00:
-
free solution
- *:
-
ref. to balance state
References
W. Vielstich, ‘Brennstoffelemente’, Verlag Chemie, Weinheim/Bergstrasse, 1955, chapter 4.
V. S. Bagotzky, M. S. Beletsky, Yu. M. Volfkovichet al., Inzh.-Fis. Zhurnal,21 (1971) 627.
V. S. Bagotzky, Yu. M. Volfkovich, L. M. Pismen and S. I. Kuchanov,Elektrokhimiya,8 (1972) 1013.
L. M. Pismen and S. I. Kuchanov,Doklady AN SSSR,203 (1972) 163.
N. S. Lidorenko and V. L. Onishchuk,Doklady AN SSSR,201 (1971) 1389.
I. A. Kukushkina, G. V. Shteinberg, Yu. M. Volfkovich and V. S. Bagotzky,Elektrokhimiya,8 (1972) 1451.
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Bagotzky, V.S., Volfkovich, Y.M. Mass exchange in a hydrogen-oxygen fuel cell with a capillary membrane. J Appl Electrochem 2, 315–325 (1972). https://doi.org/10.1007/BF00615279
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DOI: https://doi.org/10.1007/BF00615279