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1 (a) Plot the j-V curve for an anode-supported SOFC that has a 1000-yim-thick anode and a 50-um-thick cathode. Consider both the anodic and the cathodic overvolt- ages by using Equations 6.27 and 6.67. Use the properties provided in Table 6.4. (Assume that the Table 6.4 jo and a values apply to the SOFC cathode. For the SOFC anode, use jo.A = 10 A/cm2 and ag = 0.5.) (b) Plot the anodic overvoltage and cathodic overvoltage for this fuel cell. (c) Find the limiting current for each overvoltage curve. Which electrode shows more loss? Explain the consequence of ignoring the anodic overpotential in an anode-supported SOFC.
ј RT cathode = 4aF --I love ) In (6.27) loPC {xo,la - CRT/ (4Fp© D...) (0₂,N2 (6.67) RT j Manode = 2aF JOPA | XH₂ la - (A. ( jRT – 2 Fpa Deff H2,H20
values 1.0 1073 0.95 0.21 #.#20(m/s) riysical properues Thermodynamic voltage, Ethermo (V) Temperature, T(K) Hydrogen inlet mole fraction, Xhela Oxygen inlet mole fraction, xo, la Cathode pressure, patm) Anode pressure, patm) Effective hydrogen (or water) diffusivity, Dall Effective oxygen diffusivity, D, (m²/s) Transfer coefficient, a Exchange current density,j,(A/cmº) Electrolyte constant. Asorc(K/2 m) Electrolyte activation energy, AG (kJ/mol) Electrolyte thickness. (um) Anode thickness, (um) Cathode thickness (um) Gas constant, R (J/mol · K) Faraday constant, F(C/mol) 1 1x 10-4 2 x 10-5 0.5 0.1 act 9 x 107 100 20 50 800 8.314 96,485