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Anode and cathode metals? (For electrolysis) Answered

I want to seperate some water to get Hydrogen to play with, so I made a little electrolysis device with a 12v power supply. The only problem is that I have no idea what to use as the anode and cathode! Could I just use screws? Or pennies or something?

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Commercial and house hold electrolysis anodes are usually made of titanium. It does not deteriorate at all. You can buy titanium scrap and plate on ebay and from a place I use 'Onlinemetals.com" It is not overly expensive in thin cross section, like 20 gauge sheet. If you are going strictly for water decomposition, use material for your electrodes that is the same, for example, tin can metal. It is cheap, readily available. Be sure to sand off the coating on the inside. Works great, is free and does not deteriorate very fast (so long as both anode and cathode are the same metal). For electrolyte, use washing soda, baking soda or (with more caution, gloves and goggles) liquid plumber {which is just liquid lye} - use the cheap grade, like a store brand) Salt is also pretty good, even though some folks think salt is not a good electrolyte- but, the problem is, the salt will also turn into sodium hydroxide during the process- so again, use caution. Yes, eventually, your "tin can" electrodes will dissolve. But, they are cheap (basically free) and easy to replace. If you are building a generator you want to keep and use over and over or continuously, use the titanium electrodes and they will last basically forever. Do not let your conductors, copper wire, I presume, touch the liquid electrolyte. It will also dissolve with time. Be sure to replace your electrolyte occasionally, it does change over time and can become toxic. Since it is cheap and easy to make, simply add a fresh batch and start over frequently as you see too much color change or odor. Be sure to do this experiment in plenty of ventilation to keep dangerous fumes from building up. Don't forget (duh!). the byproducts of the process- hydrogen is flammable and when mixed with the oxygen, it is explosive.

I am mostly interested in making oxygen. Can I use H2O2-KOH solution for electrolysis? I will be making a battery pack using NiMH batteries so I can charge it at home, and carry it in my car. I don't think my car electrical system will be able to handle the load over a long period safely. What do you think of this idea?

Is it ok to use the same metal as anode and cathode for electrolysis? I am goin to make a sodium chlorate from sodium hypochlorate(bleach).

Use an unreactive metal like gold

When I was younger I used the carbon rods from HEAVY DUTY D CELL batteries. Gently smash them open with a hammer.
Break off all the maganese oxide and pull out the carbon rod.
You can solder leads to the caps. Dollar Sore 2 for a buck!
Do wear rubber gloves !!!

I have also used titanium. . .Ebay Two - Grade 2 - 3inch piece2 = $5

Hint:
These things are actually compressed carbon dust and they use a binder.
They also love to soak up the electrolyte from the battery.
For serious applications I suggest to use a good blow torch on them first to get them to a nice red glow.
Doing so burns out all unwanted stuff that would otherwise contaminate whatever you use for the reaction.
Since the caps get lost in process I used stainless steel wire to hold them.
A great alternative for small scale are the carbon brushes you get as cheap replacements for drills and other things on Ebay.
And as you said titanium is always a good choice.

Please ignore older posts recommending Stainless Steel. Never ever use Stainless Steel in electrolysis! This will create Hexavalent chromium which is extremely toxic and highly carcinogenic. It is also illegal to have and dispose of.

Using copper electrodes will produce chlorine gas and it's poisonous when inhaled. They used it as a chemical weapon in World War 1.

I did some electrolysis experiments with a friend a few weeks ago. We mixed vinegar and salt, and used a 12V power supply with copper wires. It barely produced any bubbles - not anything harmful since we were in fairly well a ventilated area anyway...

I now know not to use salt, but copper produces chlorine gas too? What CAN I use!?

The best thing to use is Platinum, but who has that lying around? Graphite is the next best thing, and it's more readily available:

http://www.ebay.co.uk/itm/5PCS-99-99-Black-Graphit...

When it comes to the more hazardous metals such as stainless steel, it really depends on the scale when determining how hazardous it is. If you're working on a large / industrial scale then sure, it's really dangerous. If it's on a small scale then the risk is greatly reduced. But like most things, if the risk can be eliminated, why take the risk.

That's way cheaper than I thought it would. I did it in a 50ml beaker, so I think a pencil lead will be fine. Thanks.

Take two spoons and then attach the battery directly at the ends of the spoons.It will work.

out of common materials, I think alluminum is the best

Do not EAT or DRINK any of that. You will make horrible heavy metal exposure into the water as it degrades the metal into sharp, cancerous, stomach ripping metals over time

which anode and cathod will make highest amount of oxygen and hydrogen i dont care about the cost tell me the best output material for hydrogen and oxygen production

No, actually Alluminium corrodes so fast you won't believe it...

So it doesn't really matter? I figures since stainless steel resists oxidizing (right?), then fewer oxygen bubbles would form and I'd get more hydrogen... Any idea? I'll try out aluminium and let you know how it works!

well, you get the same amount of hydrogen and oxygen, it's just stuff like iron and steel (not sure about stainless steel) will oxidize (rust/corode) really quickly, alluminum still will, just not as fast.

Some humidifiers pass 120v directly through the water. With AC, it apparently produces steam rather than H and O. The electrodes are carbon. In my experience trying to split water, low voltage is needed to prevent the _metal_ electrode from rapidly corroding. Corrosion seems to insulate the electrode. Carbon doesn't have this issue at higher V.

For making H and O nothing beats surface area and a constant flow to flush the forming bubbles away.
But for electroplating, anodizing and such I have to say that nothing beats the right mix of medium and electrode material.
For example copper plating with a steel donor electrode in copper sulphate solution works but the result is bad and the mix useless after this.
Platinum or titanium work much better here but still copper as the donor is best for obvious reasons.
From my experience AC is not working properly in a home setup for plating works.
However using a pulsed DC at higher voltages seems to indicate that a much better control over the process is possible.
Smaller bubbles form and I am quite sure there will be a sweet spot of voltage, current and frequency that would prevent bubbles completely.
Especially with copper I find that that a pulsed DC gives a much better surface finnish as it does look less dull.
In any case contamination is the worst to happen but the right PH level is importent too.
Try some copper plating at different PH levels and leave all other parameters the same ;)

I recently did some electroPLATING. Zinc on steel, copper on steel, an _attempt_ at zinc or copper on graphite (on paper) . An _attempt_ at plating copper directly onto a pencil lead... the most BUBBLES appeared on the pencil lead.

I've seen graphite and platinum been recommended as they wont be corroded (?), but any conductive metal will work. Mix bi-carb with the water to make it conductive, and you only need 1.23 V for electrolysis, a higher voltage with just generate more heat; more amps is what you need to create more bubbles.

I've tried it with spring from ball pen. All oxygen reacts with metal :/

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djdole

6 years ago

The different metals used for cathodes and anodes are not for electrolysis but are for acid batteries (and are usually zinc & copper).
You don't need specific metals for electrolysis, just a metal that conducts electricity, and the two electrodes don't need to be different metals (as they do if you were creating an acid battery).
The important part is having a solvent mixed with the water. (Pure water is non-conductive, so won't work.)

A little chemistry knowledge will help (polarity of hydrogen vs oxygen to identify which electrode is attracting which element).

Also be aware that certain metals will react differently in the electrolysis reaction, combining with either the oxygen or hydrogen to produce new compounds (and in doing so, corroding your electrodes over time).

For example, when I was in 6th grade I used a home-made electrolysis rig to split baking-soda water into 2 parts hydrogen to one part oxygen.
I also used large chunks of copper for my electrodes which meant that on the one polarity, some of the oxygen combined with the copper and created copper-oxide. Later I collected and concentrated the copper-oxide and used that as my solvent in the water. I then by clipping a quarter to the opposite electrode I reversed the reaction and copper-plated the quarter.
Science fun!

If I use lead as both cathode and anode so will seeing the electrical connections only help or would I have to go for testing if the other lead electrode is also attracting some hydrogen ions as well??

Hmm, everyone says carbon rods are good but in all my attempts at 'water' electrolysis the carbon anode disintegrates and doesn't produce much oxygen. There's plenty of hydrogen at the cathode - which doesn't deteriorate. I've used reclaimed battery centres and standard pencil lead, they both gradually fall apart.

Using MgSO4 for the salt it looks as if bubbles are formed at the anode but don't make it to the surface. Any ideas?

Picture shows worn battery carbon anode in foreground, disintegrating pencil lead in centre and perfectly good cathode in the background

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use stainless steel or graphite rods.

graphite_6.jpg

Use Carbon or Steel electrodes.

I have done quite a bit of anodizing and before that produced hydrogen for various experiments.

There is a lot of fance and expensive material out there that can be used, all have their good and bad sides, the later mostly in terms of being costly and hard to work with.

If neither extreme efficiency, nor extreme outputs are required you make a quite simple setup that takes out most of the contaminants that happen from corrosion.

Also it should be noted that the type of "salt" you add to the water plays a vital role to keep corrosion at a minimum.
For example sodium chloride is often used by starters, I prefer a just a few drops of Phosphoric Acid (rust remover).
As for the setup I used to produce small amounts of both oxygen and hydrogen:
Two 2L plastic bottles (one for O the other for H), connected with two hoses and a little in-line pump.

I connected the bottom hose from the first bottle to the outlet of the pump, the top hose to the bottom of the second bottle and from there the top hose back to the pump.

The pump itself was a sealed unit for the water dise with a magnetic drive, a filter capsule was attached to it - a filter is essential, but more later.

As electrodes I used just lead sheets that I rolled so they fit through the top of the bottles.

The electrical connection can be tricky if you want a proper seal, so I improvised by using hot glue to cover the wire (bend down on the bottle neck) and create an overall smooth surface on the screw top.

Gas collection was with simple balloons stuck on the top of the bottles.
The "trick" is that the connected pump not only assists to push the gas up but also filters out all solid contaminents.
Since all was sealed and a ceramic axle used there was no problem with corrosion or electrical failures within the setup.

Lead is far from perfect but it lasts quite a long time if phosphoric is used instead of salt.

I can't recommend on baking soda or even hydrochloric acid.

In a HV HHO generator normal water from the tap can be used withouth any additives but I guess that is a different topic.

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Lovot

4 years ago

The cathode can be made of regular steel because electrolysis actually reverses black rust and will not form more corrosion, in fact electrolysis is used to restore iron objects. I wouldn't suggest copper (including copper alloys) or aluminum for either electrode because they corrode rapidly when used for electrolysis. Carbon, high chrome stainless steel, chrome, any member of the platinum family, and gold all make good anode materials. The anode will definitely cost you more, if you want something that won't need a lot of maintenance and won't generate unwanted substances.

As a follow up to what Lovot has said here, when making an anode you have to choose whether you want something that's resistant to oxidation (chromium, gold, platinum) or cheap to replace without many chemical concerns (carbon).

The two properties tend to be mutually exclusive.

After that, any conductive material will work as an electrode, but certain shapes work better. You want a shape that allows for an increase in surface area. The more surface area touching a liquid, the more efficiently you will conduct electrolysis.

So... generally speaking, screws work better than nails. pennies work better then pins. you have to be conscious of the cost to fabricate a particular shape though.

You may use Stainless Steel grade 302 or grade 304 for the “Cathode” (the minus volt wire), but grade 316L is essential for the “Anode” (the plus volt wire).

If you're going to use both in one device, it is important o always make note which is which. Also remember to put a RED wingnut on the bolt connected to the 316L wire, and a BLACK wingnut on the 302/304 wire.

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I cant remember what we used in general chemistry, but we were calculating columbs and Avogadros number and all that. Save the water that is left over because it has a higher % of "heavy water". I dont know how to make it more pure but its something to play with. :)

. For small batches of home-brew Hydrogen, electrode composition is not that important. Think of them as sacrificial and use something cheap (eg, Copper). . If you plan on making large quantities, then you may want to use something like Carbon, Platinum, &c;, as mentioned by others.

Carbon, even pencil leads, for small stuff a mechanical pencil refill pack would do alright. Platinum would be best, I suppose a serious person might use platinum spark plugs as a substitute for buying platinum rods. Silver and gold would probably do well...

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westfw

9 years ago

Probably the easiest and most inert electrode material you can get easily is a graphite or "carbon rod", like from inside an old-style ("Heavy Duty", but NOT "alkaline") battery. Graphite rods are apparently available as as welding supply (?)

They are used at extremely high amps to cut metal. The arc heats it and then the molten metal is blown out by compressed air. I use them for welding thin sheet (I even made in instuctable about it)

The perfect material would be platinum, but otherwise use carbon. I have had plenty of success with pencil-leads (the soft ones conduct better, but snap more easily), so I assume artists' charcoals will be as good.

oops, forgot about carbon, lol, my bad