Picture of Hoffman Apparatus for pure hydrogen gas
I’m sick of hydrocarbons. There are way better gasses out there that do the same job.
Did you know – the original engine by Rudolf Diesel was made to run on peanut oil, and the original T-model Ford was designed for ethanol fuel?
Anyway, enough of that. Before I can think about alternative automobile fuels, I need an efficient way of creating said alternative.

Hydrogen gas has already been used by a number of people and companies as an alternative to petrochemical fuels. The one commonly appearing in the media is the hydrogen fuel cell, whose appearance is similar to a battery (though the inner workings are very different) and produces electricity to power an electric motor.
This, however, requires a whole new car designed specifically for use with a fuel cell.
Unfortunately little known to the wider public, BMW actually has a fleet of cars – regular petrol cars only very slightly modified – running off hydrogen gas as a combustion fuel. They use exactly the same mechanism as if they were running off petrol, but it’s not petrol.

This got me thinking. My car runs on petrol. Perhaps I too could use hydrogen gas and have a car that produces absolutely no CO2 emissions. So this is my first step (don’t get too excited, it’s just a baby step) towards that future.

A Hoffman voltameter, or Hoffman apparatus, uses electrolysis to produce hydrogen and oxygen gasses from water.
By passing a DC electric current through the water (with an electrolyte solute to improve conductivity), energy is put into the water – enough so that the chemical bonds within H2O are broken and it splits and reforms into H2 and O. The O then finds another O that split from another molecule of water and forms O2. Hydrogen gas (H2) forms as bubbles at the negative cathode and oxygen gas (O2) at the positive anode, so if the two electrodes are kept slightly separate, the two gasses can be collected separately and used for good, or evil, depending on personal preference.

The following instructable contains some dangerous chemicals;

- Hydrogen gas (obviously) is a colourless, odourless, highly explosive gas. Never have a naked flame, or anything hotter than 600°, anywhere near your working area. Until you’re ready for the fun part, of course.

- Sulphuric acid is a wonderful electrolyte, but horribly dangerous if handled irresponsibly. It will burn skin and tables and faces, so always handle with the utmost care and always wear safety glasses and natural rubber (not latex) gloves.

- PVC should not be used for any purpose involving compressed gasses. It has a tendency to shatter and splinter when put under pressure. The PVC used in this instructable is simply used as feet for the apparatus and does not come into contact with any kind of pressures above atmospheric.
Remove these adsRemove these ads by Signing Up
1-40 of 115Next »
Nighthaw made it!yesterday
I was having a problem finding a battery to use. so an inexpensive alternative that won't run down is a car battery charger, works much better as it can also produce the massive amounts of current. also I used cheaper threaded metal rods and they did start rusting, however their low cost makes them much more affordable and easier to replace
v-raze4 months ago

Thank you for making a well planned, working device using quality materials and methods. I will keep this instructable as a resource in my own projects. Also, great video, dubstep is indeed amazing.

3of57 months ago
It shouldn't be co2 you are to worry about, plants take care of that, what you should be worried about is co3 and unburnt fuel.
squiggy2 (author)  3of56 months ago

What? CO3 is only produced in things like corona discharges. It's extremely unstable and lasts less than a second. What has it got to do with anything?

Plants do take care of CO2, but not fast enough. We are cutting down all the trees, and producing far to much CO2 for the remaining ones to handle. Have you been following the news over the last decade?

Unburnt fuel lowers the efficiency of your car, but it's not a huge environmental factor at the levels we get today.

eteal1111 year ago
I've done this with KOH, and got results, but you could also do this with any salt (although NaCl is crazy hazardous when broken apart)
squiggy2 (author)  eteal1111 year ago
I used to use salt water from the beach, and that's fine for small quantities, but as you said, if you want to do more than a balloon-full, you're in danger of toxic chlorine gas.
Any salt will work, but I like sulphuric acid because it isn't consumed in the reaction. Eventually you will have to replace KOH as the O evolves into oxygen gas, but sulphuric acid lasts forever
RangerJ2 years ago
SInce you are dealing with sulphuric acid, which, as you point out, is a colorless liquid, I thought I might add this bit of wisdom, by that great poet, Anon Y. Mous:

Little Willie was a chemist,
Little Willie is no more.
What he thought was H2O
was H2SO4.
hygicell3 years ago
do not EVER use PVC wit a gas !! it will burst and splinter ! exteremely dangourous !!
squiggy2 (author)  hygicell2 years ago
You're 100% right. I've edited this step
Please put not one, but several warnings in your text, so people know the risks for their other projects. The use of PVC is probibited for any gas,even for compressed air
You may want to consider using inert carbon rods (which can be found inside "super heavy duty" carbon-zinc dry cells) rather than the metal bolts you have posted above. Eventually, no matter the composition of the bolts, if they are metal, the anode will corrode and wind up deposited on the cathode. This is also the reason why batteries use carbon instead (in carbon-zinc ones)- while being excellent conductors, they won't corrode.
This is not true, Carbon reacts with the oxygen being produced forming carbon dioxide,
And not all metals are reactive.
Amigos el solo hecho de agregar oxigeno a nuestro medio ambiente, es fantástico, el producir hidrógeno por este medio tiene sus riesgos pero aun así tiene sus ganancias, yo estibe trabajando con un generador a base de hidróxido de potasio y ese si que generaba hidrógeno para enfriar un generador eléctrico de 50 MW Mega vatios con 70 amperios y con hidróxido de potasio al 6% con un voltaje de 7 a 12.
Does heating the water (perhaps, using green sources) aid in hydrogen production? Adding energy into the water /may/ cause the bonds to be a bit... weaker, but then, of course, heating is very dangerous near highly flammable gases, like hydrogen!
squiggy2 (author)  nutsandbolts_642 years ago
Yep heating would help. But you're right you don't want to have too many hotspots when you're dealing with hydrogen :P The other thing is you don't want the water to evaporate. I actually need to cool my apparatus after extended periods because the water gets close to boiling and I end up collecting small amounts of steam.
If your apparatus were pressurized, the boiling point of the water would be higher, and less cooling, or no cooling, would be needed, to avoid steam production.
hogey743 years ago
Mate, love this. A couple of comments:
1. I wanted to do that course in the early 90s but I was too chicken to move to Melbourne from North Queensland lol. I'm now doing an aviation degree in Brisbane - years later!
2. I've got a couple of brief-case style solar panels that supply about 1 - 1.5 amps @ 12v - I reckon they're what I'd run this with, maybe through a regulator.
3. Now that the storage problem is being solved, I reckon hydrogen will be huge, especially as photovoltaics get cheaper. I can see a bigger version of this setup in everyone's house. Maybe outside.
4. Thanks for the instructable!
squiggy2 (author)  hogey743 years ago
I dunno how it was back then, but these days you would be alone. There are a couple of kids in my class form townsville and longreach.

You could do something with controlling the resistance of the system, but my apparatus draws close on 10 amps, so you'd need a few panels to be able keep the volts up, I'm in the same situation so that's what I'm working on now - i'll post result when I have some.

I'm very much looking forward to hydride storage tanks, and hopefully the decriminalisation of the materials used in them. I'm can't wait until everyone is producing there own fuel at home!
Thank YOU for your support
Hydride storage at home? They're some of the most dangerous chemicals on the planet--explosions even in advanced laboratories are routine. Compressed or liquid hydrogen would probably be safer, albeit marginally.

I think compressed nitrogen is a decent route for energy storage. Sets of tanks can power tesla turbines to generate electricity to produce H2 on demand. Storing large amounts of flammable or reactive compounds is going to elicit an implacable--and warranted--NIMBY response.
While not available now, I've been reading about work on new means of storing hydrogen using a catalyst/matrix-filled tank that won't vent hydrogen even when punctured. That's what I'm talking about - something a few years off. It's apparently safe enough that it could be built into the chassis rails of cars etc. I'm expecting that the energy density of this new type of hydrogen storage will be superior to electrical batteries and that this might tip things towards hydrogen as a fuel for mobile applications.

I've heard and thought about the compressed gas battery concept too. It maybe well be the case that new houses in future start with an excavation for storage tanks. have you also seen the British work on liquid air powered reciprocating engined cars? It's actually quite exciting the energy density they are getting and it's something that could also be done using household photovoltaics, wind etc.
Liquid air is essentially liquid nitrogen, which is what I was suggesting. Do you have any sources for the catalyst/matrix mix they're using? Hydrogen venting isn't the only problem. Exposing the matrix to low amounts of oxygen can elicit a potent reaction.

I'm guessing they'd use MgH2 as a storage source, since it's far less pyrophoric than AlH4 or LiH. This paper seems to have some good ideas going for it--a self-sustaining reaction producing three moles of gaseous hydrogen for one mole of water once it's started. Still has the problem of having 60+ L of 300 C hydrogen gas shooting around, though.
Hey nice link - never heard of that process. It's not the one I'm thinking of though - the H2 was/is stored as H2. Will keep digging...
I like your instructable. Keep going for it! You should be the one to perfect it and place it into the public domain for the common man. Three cheers to Squiggy2 for effort and determination! And may you have many long years of life to achieve many great things.

(On a slightly discontented note; I remember how the press popularized some of these amazing things many decades ago when I was young.)
This metal hydride storage for low pressure Hydrogen gas has been announced as "just around the corner" for decades. I'm old enough to remember when this was a new idea waaaaay back when. Just where are those flying cars they also promised us?
Hey now you ask, I'm trying to remember where I saw this. Might have been in a New Scientist mag? I'll do some googling and get back to you. Whatever it was, the hydrogen was not released unless a small amount of heat was applied. Not enough heat to make the process useless. I specifically remember that puncturing the container did not vent gas or create other hazards...
Yeah not surprised but back then, Melbourne seemed a loooooong way away :-)

PV power really needs 4 of 5 kilowatts to power a house with spare capacity for energy storage. I like the idea of constructing a rig like yours and slowly accruing some more PV power to make a little test system with a little hydrogen tank that can run something. 10 amps? I'm about a 3rd of the way there.

BTW I've been sketching an RC blimp recently that could use that hydrogen... I'm going to call it the Hoganburg
squiggy2 (author)  hogey743 years ago
ooh ooh I've been doing the same thing! An RC blimp was sort of a side reason to get this hydrogen going. When you finish it I'd love to see the plans! (assuming you're not going to patent it :P)
ha ha great minds thinking alike! re - patent, nah, I'd say there's just a bit of "prior art" lol. I met a guy recently who has done world record home made helium balloons (as in, for real people) and I'm talking to him about this stuff ... I'll chuck ur details in my little hoganberg folder and flick you a message :-) I'm thinking balsa for the internal structure but it might start out as a blimp. btw lots of cheap, awesome, old-school RC gear on US ebay ...
Mykulitz2 years ago
I've been with this project before... The main reason why I didn't continue was not practical to be done... It consumed a lot of electrical energy just to produce a small amount of hydrogen gas... Why not using DC electrical motor instead... If you will use this as a fuel for stove it will very expensive unless you have your own power source... One more thing, I already heard that there's a kind of car today that can be run by using a 12v battery at the speed of 40km/h and if you run beyond that speed the gasoline engine will take over to run the car.. that one is cool... Your project was really amazing... Keep go on until you perfect it. If you can increase the production rate of the hydrogen by a minimal use of electric power that will be more amazing... Just believe for what you can do... Keep researching...
itzsnitz3 years ago
I have a thought experiment for you:

Assuming you had an infinite source of electrical energy available on vehicle (not produced by engine), how large would your device need to be in order to produce enough fuel to supply the needs of a vehicle at highway speeds?

Here are some assumptions to work from:

An energy consumption rate of 6MJ/min is required to maintain your vehicle's on highway speed (assumed be to 60MPH). The energy efficiency of your engine is around 15 MJ/kg for hydrogen fuel consumption (surely there's a better fuel specific unit, eh?).

1. How much gas must you produce per minute to keep your speed?
2. What size of electrode is required for this production rate?
3. What volume of water/acid is required for this production rate?

Your results will likely be on the order of, "Huge". The question then becomes, how can you reduce the size of your fuel cell while maintaining production rate, eliminating the need for storage system entirely?

Of course, there's still that "endless on vehicle electrical energy" problem, but I'm sure someone will figure that out! ;P
billhorvath3 years ago
The guys behind United Nuclear have been working on this problem. See
squiggy2 (author)  billhorvath3 years ago
Ah that's what they're called. I saw these guys a couple of years ago but forgot their name. It's a shame that they've been held up by the difficulty of getting the material they require. Perhaps we in Australia might be able to get our hands on them. I'm going to Nanjing in September, I'll see who I can talk to :P
HBSkirmit3 years ago
I've built several of these hydrogen generators and found that the law of physics hold true: you can never produce more power output than you put into it. You might be able to gain a few extra miles per gallon on a vehicle by using a combination of the hydrogen generator, oxygen sensor enhancers and mass air flow enhancer.
Also, the maintenance and upkeep required to keep the hydrogen tank clean and full of liquid are just not worth the effort. There are internet sites that explain the difference between hydrogen and gasoline. Gasoline has a longer "burnability" time during the combustion explosion, ascompared with the almost instant explosion of hydrogen. Someone will eventually build a great hydrogen generator, or engine that will work with it. Hope it's you Squiggy !
See, that's the major thing holding back hydrogen generator development! 'you can never produce more power out than you put in!' Well no 'you cannot change the laws of physics!' . See my comment below.
I *DO* think most/all of the current attempts are less cost-effective than gasoline engine, I've never built one, but from what I THINK I know about them, you'd have to buy the sulfuric acid (which is a WHOLE lot more expensive than gas)... Does that REALLY last forever?
lets assume that lasts FOREVER, and you just have to add water.
Do you have to use distilled water, which costs about a dollar a gallon, but what is it's power output compared to gas? I've READ that it's MORE than gasoline (fumes for those who want to get technical) but my little 2.0L engine (800 RPM Idle) takes 28.25 CFM of air. at 14:1 compression, that means I need 2.02 CFM or fuel (compression is different for hydrogen than gas, so this figure will differ). or 4.54 CFM if I'm actually RUNNING the engine (1800RPM)... Can it produce this much (further reading says hydrogen needs 4 times the volume of gas, so 18.16 CFM)
If we use regular tap water, does the sulfuric acid need to be filtered every so often?
how much excess energy does the alternator create? can we run multiple Hoffman Apparatuses with that excess power without overloading the alternator?
squiggy2 (author)  bac5123 years ago
The idea is not to run the apparatus from the alternator - that would indeed break physics. My plan is to have it bubbling away at home from solar panels and fill up a tank, then plug that tank into my car when I come home.

1. Yes the acid really does last forever. It's about $7 per litre here in Australia from Autobarn. I just bought 1 litre, and it will be there or the life of the apparatus

2. I use rain water for my proof of concept, and I think it should be fine for large scale too, but if you wanted to you could use distilled water. 1L of water makes 24.5L of H2, so that works out to just over 4c per gallon.

3. If you just swapped your petrol tank for a hydrogen gas tank, you would get about 85% the power of petrol, compared to propane which puts out about 75% power.
However, if you go to the effort to install a direct injection system, power output can be increased to up to 15% more than petrol
im3733 squiggy23 years ago
It may be worth pointing out that the reason that the sulfuric acid lasts (theoretically) forever is because it does not actually participate in the electrolysis, it merely acts as a catalyst, lowering the activation energy of the water, allowing it to react easier.

When you stated using "high chromium stainless steel plates", what grade were/are you referring to? I'm woefully unfamiliar with steel grades and what they mean.

Also, what is your theory on using both the oxygen and the hydrogen as fuel? Both are flammable, would the resulting energy output be really any different? Obviously the result of burning both simultaneously would be water vapor, and some condensation is guaranteed, which could be problematic eventually.
im3733 im37333 years ago
Correcting myself here. " merely acts as a catalyst, lowering the activation energy of the water, allowing it to react easier" isn't quite right.

What the acid actually does is increase the conductivity of the water, because pure H2O is not a conductor, it only can conduct electricity because of impurities, which is accomplished through the addition of sulfuric acid.

However, my previous statement, that the acid is not actually used up in the reaction, still stands.

That said, it would be better to use distilled water than tap water, because tap water (in the US, at least) is treated with chlorine and other nasty chemicals that you do not want to end up coming in contact with in any quantity (the little bit dissolved in water is harmless, usually).
squiggy2 (author)  im37333 years ago
That's right, the sulphuric acid is just an electrolyte to allow the flow of current through water. Other electrolytes, however, like salt, are preferred in the electrolysis reaction and split instead of the water.

I use rain water to avoid things like chlorine and fluorine in tap water, but if you wanted to do it absolutely you should use distilled water.

To be honest I don't know much about steel grades either as far as naming and production and things, but I do know the effects of alloying elements to steel. The chromium is what stops stainless steel from rusting. Officially "stainless" means at least 12% chromium composition, but this is the bare minimum and will still rust under extreme conditions. Medical grade stainless is up around 30% chromium. This would cost a bomb if you wanted to buy a couple of plates, but use your discretion to get something in between. The higher the chromium content, the less it wiil corrode
squiggy2 (author)  squiggy23 years ago
Ah I must correct you there.
One of the greatest misconceptions about oxygen is that it is flammable. Oxygen is not flammable. Oxygen facilitates combustion of fuels, but if you apply heat to pure oxygen, nothing will happen. If you apply oxygen to an already burning fuel, it will increase the rate of combustion - sometimes dangerously so - but that does not mean it itself is flammable.

That aside, your question was "why don't you use both the hydrogen and oxygen together?"
You're right, I could use both, which would give me a perfect stoichiometric ratio and best efficiency. But to do that I would need to compress and carry 2 fuel tanks. twice as much fuel. The air all around us is 21% oxygen - why not use that?
And we do. That's what cars use to combust their fuel.

The main losses in energy come from the electrical resistance of the system and overvoltage required to split the water molecules. Not the fact that i'm only using half the product, so to carry oxygen really is more effort than it's worth when there's plenty of it in the atmosphere
1-40 of 115Next »