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EECS – Prof. A. Casalegno – 13th January 2021 1 Basic Part (4.5 points per questions, minimum score 12) 1. Write an example of electrochemical reactions occurring in a Lithium-ion battery and the typical operating voltage range 2. Draw the electrical potential in the double layer of a PEMFC for a ORR in equilibrium 3. Depict the polarization curve of an alkaline electrolyzer with reasonable values Exercise A Li-ion battery with nominal capacity of 12,5 Ah discharges as in the figure. Assuming that: 1. Tafel kinetics is valid for both electrodes 2. ion and mass transport effects in electrodes are negligible 3. activities of reactants in discharge (or charge) are close to the value of SoC (or 1-SoC) 4. electrolyte resistance is equal to 10 mΩ 5. transfer coefficients of both electrodes during discharge are equal to 0.5 Calculate the values of C-rate A and C-rate B, approximating to integers (natural numbers). Intermediate Part (3 points per theory questions and 3.5 for the exercise) 1. Write Butler-Volmer and Tafel equations and represent on the same graph 2. Depict three polarization curves of a PEMFC operating at 70°C: 1) O2 feeding at 1 atm and RH=100%; 2) air feeding at 3 atm and RH=40%; 3) air feeding at 3 atm and RH=100%. Exercise A PEM fuel cell operates at 80°C with pure H2 and air at 0.3 MPa pressure and supplies at 0.65 V a current density equal to 2 A/cm2 and related impedance is reported in the figure. Assuming that: 1. anode behaves as an ideal H2 electrode [𝐸!+𝜂!=0] 2. ion and mass transport effects in catalyst layers are negligible 3. the average O2 molar fraction in the cathode channel is equal to 0.08 4. diffusion layer diffusivity Dref is equal to 0.05 cm2/s (at Pref=1 atm) and its thickness is 200 μm [assume D=Dref Pref/P ]. Assuming a fuel utilization…