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EECS – Prof. A. Casalegno – 2nd September 2020 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 HOR in equilibrium 3. Depict the polarization curve of a PEM electrolyzer with reasonable values Exercise A Li-ion battery with nominal capacity of 25 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 5 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. Represent the impedance spectrum of a PEMFC operating at low current and indicate where information on membrane and catalyst layer ion conductivity can be obtained. Exercise A PEM fuel cell operates at 70°C with pure H2 and air at 0.25 MPa, the portion of the cell at cathode inlet, where O2 molar fraction in the cathode channel is equal to 0.17, supplies at 0.7 V a current density equal to 1.8 A/cm2. 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. membrane ion conductivity and thickness are respectively 0.07 S/cm and 15 μm 4. transfer coefficient of ORR is equal to 0.5 5. diffusion layer diffusivity at 0.25 MPa is equal to 0.012 cm2/s…