ECCS Exam 16 6 25

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EECS – Prof. A. Casalegno – 16th June 2025 1 Standard EECS exam [duration 1 h 40 min] Students who passed TiP reduced number of questions marked with (TiP) [duration 1 h 10 min, remaining further means cancelling TiP mark] To upload https://forms.cloud.microsoft/e/n0sHcDwvU9 maximum 5 single-side A4 pages – “file name” = PERSON_CODE.pdf Basic Part (4.5 points per question, minimum score 12) (TiP: 7.5 points) 1. Write the Nernst equilibrium potential for an electrode with an acid electrolyte where OER (O2 evolution reaction) occurs. 2. Write the Nernst-Plank equation to describe the H+ molar flow in a solid electrolyte with negative fixed charges 3. (TiP) Depict the charge curve of a NiMnCo Lithium-ion battery including a period at constant voltage, indicating also reasonable values for State of Charge and voltage Exercise (TiP) A PEMFC stack operates following the reported j/V curve and supplies 20 kW at 222 V and 0.3 A cm-2(LHV=120 MJ/kg). Assuming: the single cell area equal to 300 cm2 and H2 utilization equal to 96%, estimate the efficiency and the power at the maximum current. Intermediate Part (3 points for each question) (TiP: 5 points) 1. Is the cathode overpotential of a PEM electrolyzer positive or negative when H2 evolution reaction (HER) occurs? Demonstrate analyzing 𝐺̃ 2. (TiP) Depict as a function of SoC both the positive and negative electrode overpotentials of a Lithium-ion battery, during discharge, and indicate a general criterium to assume acceptable Tafel kinetics. ∆𝑉 0 𝑗 0.78 V 0.67 V 0.3 A cm -2 2 A cm -2 EECS – Prof. A. Casalegno – 16th June 2025 2 Exercise (TiP) A Li-ion battery with nominal capacity of 5 0 Ah operates at ambient pressure and temperature, supplying 3.45 V during discharge at SoC= 70% and C-rate=1.5 and requiring 3.9 V during…