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.
Step 1: Materials
All of the materials below have been chosen for their resistance to sulphuric acid. If you want to change some of the components in your own design, check the new material for its resistance to H2SO4.
5 mm thick Perspex sheet – around 500mm * 300mm of the stuff
2 high chromium stainless steel plates, 140mm*120mm, bent at 90° 20mm in from the long end. Don’t skimp on quality, you need the high chromium stuff or it will go rusty in minutes.
4 Stainless steel bolts and corresponding nuts ~30mm long and 10mm in diameter
4 Hose clamps – you know, the ones you screw with a screwdriver to tighten
8 Aluminium L bracket 100mm in length
An old bicycle tyre inner tube or other thin natural (not neoprene) rubber sheet
Scrap PVC pipe ~20mm diameter
The end of a PVC pipe threaded on the outside, and corresponding screw cap 50-80mm diameter
And 2 more threaded pipes + caps ~20mm diameter
~1m really thick wire. We’re talking 2+mm diameter of the copper, not including insulation
Two of those battery connectors that you crimp onto the wire, or alligator clamps.
A car battery or something else capable of supplying 12 volts DC an a lot of current. A computer power supply is not suitable, as the amount of current the Hoffman apparatus draws will (and did) blow up the power supply. 12 volts is an arbitrary number, but H2O requires a minimum 5 volts to split, and the higher the voltage, the faster your reaction, but the more heat will be generated. I tried a 50 volt DC converter, but the wires leading from the wall to the converter got unnervingly hot.
1 – 3 litres of sulphuric acid. This is marketed as car battery acid or electrolyte. Sometimes it is sold as industrial strength acid drain cleaner, but so is hydrochloric acid, and you MUST NOT USE HYDROCHLORIC ACID. Instead of the electrolysis producing hydrogen gas and oxygen gas, it will prefer hydrogen and chlorine. Chlorine gas was used in the First World War because it burns soft, moist flesh like lungs and eyes. It was subsequently banned from warfare and labeled inhumane. Go for battery electrolyte. If you get drain cleaner make sure you know for sure it is sulphuric acid.
I say 1-3 litres because, depending on your finances and level of clumsiness, you can choose to buy 1 litre and dilute it with 2 litres of water, or buy 3 litres. Optimum performance comes at a concentration of 31% sulphuric acid by weight. Any more or less and the electrical resistance of the system increases, though not by a huge amount. I diluted my acid to make it safer and cheaper, and ended up with about 12% acid by weight, and I produce (very) roughly 2-3 litres per minute of hydrogen gas.
Other people use safer electrolytes like salt or bicarb soda, but these have drawbacks. Using salt also produces chlorine gas, and bicarb produces carbon dioxide, nullifying the idea of green energy. The other drawback is that these electrolytes are consumed and must be topped up every so often. Sulphuric acid is not consumed in the reaction, so once you’ve bought it, it’s there forever unless you spill it. Therefore, as long as it is handled responsibly, in my opinion, sulphuric acid is the best electrolyte to use.
Sulphuric acid is a colourless liquid when you buy it, but trace amounts of rust from inferior stainless steel have discoloured my batch.
Silicone bathroom sealant (must be silicone, not polymer sealant)
Looooots of araldite (or other) 2 part epoxy glue
----- Things which I used but would suggest NOT using -----
Gas taps from a camping stove. I thought it would be good to be able to turn the gas flow on and off, but it just ended up in me forgetting they were closed, building up too much pressure and bursting a hole in the body of the apparatus. I would suggest open PVC pipes.
Jug plugs. I wanted the wires to be removable to make everything neater when not in use, but the plugs actually turned out to be the weakest link, having the highest resistance of the whole thing and heated up too much. I have since revised the design and clamped the thick wire directly to the electrode bolts. The plugs still pop up in some of the photos though.
Case clamps. I tried to have a removable lid, so I bought some case clamps and tried a number of different gaskets including silicone sealant, inner tube rubber, neoprene gasket, bits of yoga mat, camping mat + inner tube rubber, and then gave up because the clamps couldn’t provide enough force to seal properly and I couldn’t stop it leaking.
I ended up gluing the lid on. Perhaps you could try bolting the lid on evenly all around the edges.