Water electrolyser electrode material

[Rhannmah]

I've been trying to build a closed system water electrolyser with easily available materials which allows me to collect the gases separately. To do so, I've been meaning to build an acrylic housing with a textile separator in the middle of two compartments which houses the anode and cathode. The purpose of this is to allow the electrolyte to pass through while leaving the gases separate. I want to build a setup that creates a lot of gas so I don't have to wait hours until i get a liter of gas, so the electrodes will be about 6in x 6in in surface.

The problem I've been having with this project though is selecting the correct electrode material. I have very low monetary resources so I'd like to get some help on this topic before I buy any more materials that would turn out to be a mistake.

I first looked at stainless steel, but I've learned that this produces hexavalent chromium in the electrolyte which can be toxic, so i'd like to avoid that if possible. Also, I question the durability of stainless steel in the long term.

I looked into graphite electrodes, but I'm unsure whether the material is capable of withstanding oxygen production without disintegrating within a couple hours of use. I did some tests with grafoil before investing in isomolded plates; it works well, the quantity of gas produced for a given voltage(5 or 12 volts, as I'm using a computer power supply to power my electrolysis tests) is pretty high, but the "foil"(more like paper)takes water and gets soggy and the graphite erodes really fast and just floats everywhere. Should I expect similar results with graphite electrode plates?

Last thing i looked into is platinum electrodes, which seem to be the best for this application. They don't corrode, they don't erode, they seem to enable gas production the most and they are prohibitively expensive. Would platinized titanium electrodes work just as well without degradation? Are there any voltage/amperage considerations?

Any insight into this topic would be much appreciated.

 

[Rhannmah]

Should this be posted in the Materials and Chemical Engineering forum instead?

 

[NascentOxygen]

I expect, regardless of your choice of electrode material, you'll keep coming up against a limit on the volume rate of gas evolution caused by an insulating layer of gas bubbles adhering to the electrode surface. I don't know what is done in industrial gas production, but I think they'd need to be constantly dislodging the bubbles by shaking the electrode (perhaps by sonic vibrations) or directing jets of liquid against it.

I can't comment on suitability of electrode materials, but I expect carbon will erode. Lead can be used in electrolysis, the oxide coating that forms on the anode is itself conductive. Though you imply that toxic contamination may be a problem.

 

[Nidum]

I[/PLAIN] came across this principle recently while researching on site production of welding gasses :

https://en.wikipedia.org/wiki/Polymer_electrolyte_membrane_electrolysis

 

[Rhannmah]

This is a DIY home project, so access to exotic materials is quite limited. PEM electrolysis is really interesting, but this isn't something i can build at home. The best i can reasonably get access to is something like those : http://www.ebay.com/sch/i.html?_fro...G|2|0&_nkw=platinized+titanium+anode&_sacat=0

but i want to make sure this is going to work before i make the investment.

 

[Nidum]

https://www.google.co.uk/search?q=n...&oe=utf-8&gws_rd=cr&ei=_j0NVobAC4Gz-AHb5pfoCw

 

[Rhannmah]

Really interesting, NiFe oxide seems really simple until you read the paper that was published recently on the subject that explains how these were built. Seems like a REALLY promising approach though, but I don't think I can do this at home.

I expect, regardless of your choice of electrode material, you'll keep coming up against a limit on the volume rate of gas evolution caused by an insulating layer of gas bubbles adhering to the electrode surface. I don't know what is done in industrial gas production, but I think they'd need to be constantly dislodging the bubbles by shaking the electrode (perhaps by sonic vibrations) or directing jets of liquid against it.

About this, there are a couple techniques to deal with that problem; sonic emitter seems to be one, using pulsed DC is another. Electrode orientation also helps, if you set it up like horizontal window blinds with the top of each piece of the electrode towards the back, the gas can escape towards the back instead of in front of the electrode where it impedes ion transfer.

 

[Rhannmah]

Also, I'm wondering if a mesh instead of a plate would yield more gas.

 

[Rhannmah]

Actually, thinking about it, I think a mesh, especially a fine one, would be worse because it would trap gas bubbles in the mesh, effectively reducing electrode surface area