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Electrodes best suited to split water


A discussion started in 2006 and continuing through 2017 . . .

(2006)

Q. I want to split water by electrical means. What electrodes would be best suited. The bath must remain clean at all times. Thank you,

MIKE SANTO
SANTO INDUSTRIES - MADEIRA BEACH, FLORIDA


(2006)

A. They are not cheap, but I would expect platinum clad titanium anodes to be quite durable.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2006)

A. From my days at school, in the dim and distant past, I have a recollection of electrolysing water using simple graphite electrodes.

Brian Terry
Aerospace - Yeovil, Somerset, UK


(2006)

A. The best electrodes are made from platinum, but this is expensive, especially if you need large areas, so a common cheaper answer is to use platinised titanium, which is titanium coated in a thin layer of platinum. For real cheapness, use graphite, but this will ultimately disintegrate. Most other metals will either oxidise or dissolve and become progressively more useless.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


(2007)

A. The answer depends on what you want to achieve.
For simple experimental purposes, stainless steel is cheap and practical.
If you are considering a serious commercial application you will find that most commercial electrolyzers operate in alkaline conditions (KOH) and use either steel electrodes or nickel plated steel. To be commercially viable requires a low operating voltage i.e., low discharge overpotential. There is a great deal of information in Modern Aspects of electrochemistry No 15 Ed ralph White et al Published by Plenum Press.
Alternatively, you could buy one ready made from Brown Boveri, DeNora, Lurgi, Norsk Hydro, The Electrolyzer Corp., Telydyne etc

geoff smith
Geoff Smith
Hampshire,
       England



(2007) -- appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi,

I am looking into making hydrogen by way of water electrolysis. I have been reading about Platinum electrodes needed to make this happen. If you could point me in the right direction to buy these parts it would be greatly appreciated. I want to start off small, maybe enough to run a generator, and then maybe large enough to run a car. I thought a mesh would give me more area touching the water. Also if you know of any good books or sites with info about this it would be appreciated.

I am an electrician by trade.

Randy Bush
Electrician - New Freedom, Pennsylvania, USA


(2007)

A. There are many sites on the topic of powering cars from water/hydrogen, Randy. Put 'hydrogen from water' into your search engine. But there are as many quack sites as there are useful sites. The way you can tell the difference is that the quack sites claim or imply that a conspiracy by the oil companies, car companies, and government is "preventing you from using this free energy source". The valid sites will explain thermodynamic principles and that to generate hydrogen from water requires you to put more energy in than you will get out from burning the hydrogen. You probably also know that electrical heat costs a lot compared to oil or gas because of the large energy losses in transmission -- so that powering your car from hydrogen from the electrolysis of water with electricity that you get from your home outlets may cost more than gasoline.

So if you want to play with the concept of hydrogen power, may I suggest that you consider novel approaches like using solar heat plus a catalyst to convert solar energy directly to the liberation of hydrogen from water. You still can't get more energy out of burning the hydrogen than you collected from the sun, but at least you don't have to eat the transmission losses in electrical lines. Good luck!

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Palladium over silver?

December 2, 2016

Q. We're trying to plate a pair of small metal electrodes that must survive in a salt water environment with an impressed voltage between them. The outside surface needs to remain conductive without developing a non-conductive oxide or layer. We've been testing a copper electrode that has 150 microns of nickel, then 60 microns of gold, and then 20 microns of rhodium. The impressed voltage is less than a volt and is pulsed once every 15 minutes. The plating fails and we're getting corrosion of the copper core after a couple of weeks in seawater. We've been talking about trying silver for the base part and then plating palladium or platinum in order to have materials that are closer together on the electropotential table. Do you have any suggestions for materials or plating?

Alan Kirkpatrick
engineer - South Burlington, Vermont, USA
  ^- Privately contact this inquirer -^


December 2016

A. Hi Alan. You might put your electrodes in salt water with the current off for a couple of weeks as a test, because I don't think galvanic corrosion is the issue, but rather de-plating caused by the impressed voltage.

If the electrodes don't have to carry heavy current you could try platinum-clad titanium because they won't de-plate under most conditions. If titanium can't carry the current, you would probably have to platinum plate copper electrodes -- but electrodeposition of platinum isn't easy.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


December 5, 2016

A. You might try platinum clad niobium for this application.

Lyle Kirman
Consultant - Cleveland Heights


December 5, 2016

Q. I think of cladding as being heavier than plating? How is the cladding applied?
I like the idea of testing without power applied and I'll give that a try. The power is low and is only used to determine the electrical conductivity of the seawater, but testing without power will eliminate a variable.
We have another requirement that I failed to mention in my initial question. The material must have a fairly high thermal conductivity, and that's why we've used copper and we're looking at silver for the core part. That currently eliminates titanium and stainless from consideration. Niobium (54 W/mK) may work, but a higher Tc would be better.
Thanks for the help.

alan kirkpatrick [returning]
- shelburne, Vermont, usa


December 2016

A. Hi Alan. It doesn't take much voltage to de-plate a metal, so I think the experiment will prove informative.

"Cladding" requires a thick enough covering that it be completely non-porous and pinhole-free even after allowing for some erosion and corrosion. Some types of cladding are done by autoclaving a skin of one material onto another material, and then rolling them down to thinner gauges.

But years ago I was tangentially involved in the installation of an electroplating line at a manufacturer of Dimensionally Stable Anodes, so I know that clad anodes can be manufactured by electroplating, although I am not familiar with the chemistry that they employed.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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