ECCS Exam 5 9 22

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EECS – Prof. A. Casalegno – 5th September 2022 1 Standard EECS exam [duration 1 h 40 min] To upload (maximum 5 single-side A4 pages – PDF file name MUST BEGIN with person code) Basic Part (4.5 points per question, 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 the ORR in equilibrium 3. Depict the polarization curve of an alkaline electrolyzer with reasonable values Exercise A Li-ion battery with nominal capacity of 15 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 voltage value at C-rate B (approximated to a natural number) and SoC=20%. Intermediate Part (3 points per question) 1. Write Butler-Volmer and Tafel equations and represent them 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. !"#0% ∆% 2.75 V 4%20% 100%50% 3.55 V3.06 V 2.92 V 3 V 2.85 V C-rate=0.5 EECS – Prof. A. Casalegno – 5th September 2022 2 Exercise A PEM fuel cell operates at 80°C with pure H2 and air at 0.3 MPa, the portion of the cell at cathode inlet, where O2 molar fraction in the cathode channel is equal to 0.2, supplies at 0.7 V a current density equal to 2 A/cm2. Assuming that: 1. anode behaves as an ideal H2 electrode (!!+#!=0) 2. ion and mass transport effects in…