Water electrolysis : DIY Experiments [#5] Make hydrogen / Brown's Gas / HHO generator / Oxyhydrogen
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This is a dangerous experiment. If you wish to carry it out yourself, remember: safety first. We take no responsibility for accidents caused by improper handling.
First, we’ll produce a continuous flame using our electrolyser, then we’ll teach you how to make explosive foam and, last but not least, we’ll explain how all of this works and how it’s made. Using electricity, the electrolysis of water breaks the H2O molecule to generate dihydrogen H2 and dioxygen O2.
Run the system for 1 second to collect the large quantity of energy stored in the gases. We made a tip which allows us to directly burn the gases. The flame is small, but it is way hotter than a flame created using wood or natural gas. It’s more than 2500º C hot, enough to melt almost any metal.
Light the hydrogen flame with a lighter. A lighter flame barely reddens the spring, while it turns to liquid when exposed to a hydrogen flame.
The contact between the flame and the metal is weak, but the flame is so hot that after a while, the plastic around it melts. For this reason, we built a mini water-cooler. We let a little air in, and the water begins to flow. Now, instead of burning the gases as they are produced, we’ll collect a small quantity and release all the energy at once.
Pure water isn’t conductive and can’t be used to achieve electrolysis. We simply add a little sodium hydroxide, which is easily found in store, marketed as liquid pipe unblocker.
It contains HO ions which allow the current to flow without wearing out the zinc plates. As we saw earlier, it works alright with the liquid unblocker, but the gel one contains additives that create, with electrolysis, foam containing both gases. This is a good thing because the foam isn’t volatile (unlike the gas) so it can be used to store energy. In a few seconds, we already have a jar full of foam.
And now, we’ll release all the energy contained in the foam. I’ll take a small quantity and…we’ll ignite 2 ml of it to create an explosion. Things are getting serious!
Now, for a new challenge, we’ll fill this box with explosive foam.
It’s now time to show you how the electrolyser works. Like we mentioned earlier, we use sodium hydroxide, a basic compound, to make the water conductive. NEVER use salt. It damages the electrodes and releases chlorine, which is toxic.
With electrolysis, only the current (the number of amperes) is proportional to the production of a gas. That’s why we need a power supply capable of delivering a strong current.
And tension, in all of this? Well, we need to get 1.23 volts at the bounds of each cell for the chemical reaction to happen. That’s why we arrange more than one electrolyser in a linear way. In our case there are 4, so each one gets 3 volts. We could have used more than 4, but a voltage margin is needed for the current to flow.
For the current to be high with 3 volts only, each cell needs to have a weak internal resistance. That’s why we used multiple zinc plates. They need to be as close to one another as possible, without touching each other.
What happens on the atomic level? To simplify, picture each cell containing only 2 zinc plates. A chemical reaction takes place around each of those plates. According to convention, electrical current moves from negative to positive but the electrons move from positive to negative.
The plate on the negative side receives electrons; the water reacts with those electrons, generating dihydrogen and another compound. Around the plate on the positive side, the water turns into dioxygen and another compound and releases electrons. The first reaction uses up 2 electrons while the second one releases 4.
For the sake of coherence, the first reaction needs to take place 2 times faster than the second one. That’s why we produce 2x more dihydrogen than dioxygen. It’s the exact proportion needed for both to burn simultaneously.
In the end, both compounds we have here can react together to create water, making the final reaction 2 water molecules, that generate 2 molecules of dihydrogen and 1 molecule of dioxygen. Each time this reaction takes place, the equivalent of 4 electrons move from the negative side to the positive side.
Each electron carries a very weak charge, but when 1 faraday has flowed, we know that 1 mole of electron has flowed too. And we need 4 moles of electrons to flow to release 2 moles of dihydrogen and 1 of dioxygen.
1 mole of gas corresponds to 24L, meaning that our electrolyser generates up to 3,2 ml of gas per second, and that when we produce 1L of gas, the water level inside each cell only goes down 0.009 mm.