PEM Water Electrolysis
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Transcript of PEM Water Electrolysis
Proton Exchange Membrane Water ElectrolysisPresentation by Rich SmithEE 295 Carbon Free Electric Power
Water Electrolysis
● Production of homonuclear diatomic molecules: hydrogen and oxygen gas.
● Requires H2O and electric energy inputs.
● Recent interest in production of hydrogen as an energy carrier.
Electrochemical Reactions
● Overall chemical equation:
● Oxygen Evolution Reaction(OER):
● Hydrogen Reduction Reaction(HRR):
Thermodynamics
The enthalpy of the overall reaction (ΔH) is a combination of the water dissociation reaction change of Gibbs free energy (ΔGd) and the resulting entropy (TΔS).
Overall Cell Reaction
The overall cell equation with the addition of the thermodynamic energy input is:
Thermodynamic Values of Water
Enthalpy ΔH = 285.8 kJ/mol
Entropy TΔS = 48.6 kJ/mol
Gibbs Free Energy ΔG = 237.2 kJ/mol
Required Cell Voltage
The minimum required cell voltage can be calculated considering all possible heat energy is provided. Though operational cell voltages need to accommodate for overpotentials.
Gas Diffusion Layer (GDL)
Function:Mass Transport of ReactantsConductive Link between Electrode andBipolar plates.Balances liquid and gaseous H2O
Membrane Electrode Assembly (MEA)
Consists of two electrode layers on either side of a proton conductive membrane.
Location of electrochemical reactions.Electrocatalyst facilitate electrochemical reactions.
Proton Conductive Membrane
Allow movement of hydronium ion without conducting electrons.
Nafion Membranes 115, 117, 212
Hydrophilic sulfonated groups Hydrophobic teflon backbone