A research group intends to use a photovoltaic (PV) panel to power the electrolysis…
CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry
Problem
A research group intends to use a photovoltaic (PV) panel to power the electrolysis of water for hydrogen fuel production. The PV panel delivers a constant electrical power of 120 W under full sunlight. The targeted production rate is 0.050 mol of H₂(g) per hour at 298 K and 1 bar.
For water splitting under these conditions, assume the following half-reactions dominate:
2 H₂O(l) + 2 e⁻ → H₂(g) + 2 OH⁻(aq) (E° = –0.83 V)
O₂(g) + 2 H₂O(l) + 4 e⁻ → 4 OH⁻(aq) (E° = +0.40 V)
Faraday’s constant is F = 96 485 C mol⁻¹.
(a) Calculate the minimum electrical work (in kJ) that must be supplied to produce 0.050 mol of H₂(g) under standard conditions, assuming 100 % efficiency and no overpotential losses.
(b) Using the power output of the PV panel, determine the minimum continuous operating time (in minutes) required to supply the electrical work calculated in part (a).
(c) In practice, significant overpotentials increase the required cell voltage. Identify TWO experimental modifications (other than using a larger PV panel) that could lower the external energy demand of the electrolysis setup, and justify each choice in terms of electrochemical principles.