- #1
HelloCthulhu
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I've been studying PEM fuel cells for a while and wondered if they could be used for electrolysis. I was surprised at first to find out the technique had been used for decades, but after watching this animation the dynamics make much more sense:
https://en.wikipedia.org/wiki/Polym...lectrolysis#/media/File:PEM_Elektrolyse_5.gif
However, my understanding of electronegativity, voltage, and efficiency is still lacking for both fuel cells and electrolyzers. Wiki ranges the cell voltage for an electrolyzer at 1.75-2.20 V and the range of efficiency at 57-69%. I know that splitting a mole of liquid water to produce a mole of hydrogen at 25°C requires 285.8 kJ of input energy for a battery—237.2 kJ as electricity and 48.6 kJ as heat. And that cell voltage is 1.48V at standard atm and temperature:
[tex]E_o=\frac{(∆_f H)}{zF}=\frac{285,840 J/mol}{2*96,485 C/mol}=1.48Volts/cell[/tex]
The question I have is regarding half-cell potential and electronegativity. In terms of voltage, why is the hydrogen attracted to the cathode side of the cell? How does this affect the efficiency of the cell? I'm trying to use a galvanic cell as reference, but, since hydrogen isn't losing it's proton in solution the same way copper and zinc do in the example, I'm still finding myself confused.
https://en.wikipedia.org/wiki/Galvanic_cell
https://en.wikipedia.org/wiki/Polym...lectrolysis#/media/File:PEM_Elektrolyse_5.gif
However, my understanding of electronegativity, voltage, and efficiency is still lacking for both fuel cells and electrolyzers. Wiki ranges the cell voltage for an electrolyzer at 1.75-2.20 V and the range of efficiency at 57-69%. I know that splitting a mole of liquid water to produce a mole of hydrogen at 25°C requires 285.8 kJ of input energy for a battery—237.2 kJ as electricity and 48.6 kJ as heat. And that cell voltage is 1.48V at standard atm and temperature:
[tex]E_o=\frac{(∆_f H)}{zF}=\frac{285,840 J/mol}{2*96,485 C/mol}=1.48Volts/cell[/tex]
The question I have is regarding half-cell potential and electronegativity. In terms of voltage, why is the hydrogen attracted to the cathode side of the cell? How does this affect the efficiency of the cell? I'm trying to use a galvanic cell as reference, but, since hydrogen isn't losing it's proton in solution the same way copper and zinc do in the example, I'm still finding myself confused.
https://en.wikipedia.org/wiki/Galvanic_cell
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