MASS TRANSFER IN POROUS GAS DIFFUSION ELECTRODES. I. MASS TRANSFER THROUGH A SINGLE CYLINDRICAL PORE TO A SEMI-INFINITE REACTIVE ANNULUS.
Summary rept. no. 8,
FLORIDA UNIV GAINESVILLE
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The object of this investigation was to develop and solve a mathematical model of the mass trans fer processes that occur in porous gas diffusion electrodes. In summary, the work covered in this report leads to the following conclusions for the system O2 gas-water at one atmosphere pressure and 300 K and the model of a single pore of uni form circular cross-section, closed at its end by a plane surface of electrolyte, and surrounded by a semi-infinite annular electrode at right angles to the pore axis at which instantaneous and ir reversible reaction is assumed to occur 1 the maximum current density supportable by mass transport of oxygen to the reactive site is cal culated to be 1.45 ampssq for a pore length electrode thickness of 0.1 cm 2 the optimum pore radius is calculated to be 1.80 x cm 180 A 3 if the pore length is increased by a factor of ten, either through increase in electrode thick ness or of pore tortuosity, the current density supportable by mass transport will be reduced to about 0.5 ampssq cm and 4 the gas in the pore is in Knudsen flow. Therefore, impurities in the gas, and back diffusion of gaseous products will not affect the current density supportable by mass transport. Author