Triple electrode cell for energy storage and H2 production

  • #1
synch
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TL;DR Summary
Putting three electrodes in a cell might enable H2 production and energy storage in the same device?
Just floating an idea.

H2 production by electrolysis uses a lot of energy particularly as it usually produces oxygen as well. The energy required to produce the oxygen is usually wasted.

So, the idea is to have a cell that has a H2 production electrode as normal, but uses an opposite lead-oxide electrode to store the energy used, instead of bubbling oxygen off. So when current is pushed through the cell, hydrogen is evolved and the lead-oxide electrode charges as per ordinary lead-acid battery, storing energy in the lead-oxide reaction. This is fairly robust and would accept changeable energy availability, eg daytime solar/wind, and produces H2 for heating, cooking etc. This would typically take 2 or so volts.

The third electrode is a (eg) methanol electrode as typically used for a direct-methanol fuel cell. This is used as a counter electrode for the discharge of the lead oxide electrode. This would typically be suitable for a steady slow rate energy production, eg overnight, available for baseload and car charging etc. The theoretical potential would be the combined lead oxide and methanol cell potentials of course, I think the methanol reaction has a significant overpotential at reasonable current rates but most of the charging energy should be available on discharge.

Effectively the methanol reaction is used as an assistant The need for a finicky oxygen reduction electrode that is usually part of a methanol fuel cell is avoided.

The three electrodes would be in the electrolyte (sulfuric acid) presumably with the lead oxide electrode in the middle and the H2 and methanol electrodes on each side.

It seems to have a few synergies, then again I wonder if it would be cost-effective. As I say, just an idea.
 
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  • #2
Explanation In more detail:
The cell has three electrodes. It has

1) a hydrogen evolution electrode, to evolve hydrogen, as used in an electrolysis cell
2) a lead/lead oxide electrode, to store power, as used in a lead acid battery
3) a methanol electrode, as used in a DMFC ( direct methanol fuel cell ), to act as counter electrode for the lead/oxide electrode,

Initially the methanol electrode is disconnected.
When external power is available it is fed to the hydrogen and lead electrodes, used as a combined electrolysis / storage cell.
Hydrogen is evolved and lead oxide is formed at the lead electrode, standard lead/acid.

2 H+ + 2e -> H2

PbSO4 +2 H2O -> PbO2 + 4H+ +2e + SO4--

After the lead electrode is fully charged, the methanol electrode is connected and the hydrogen electrode is disconnected.
The combination of the lead electrode and methanol electrode then acts as a power source, mainly provided by the lead/oxide discharge reaction, using the methanol electrode as an electron source.

PbO2 + 4H+ +2e + SO4-- -> PbSO4 +2 H2O

CH3OH + H2O -> CO2 + 6H+ +6e


Overall (a little) methanol is converted to hydrogen and CO2, but in the process a lot of say solar/wind energy is stored and made available.
 

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