[Petrochemicals (OP)]

With hydrogen power touted as a green technology to save the world, how is the electrolysis of water done safely? The environment of water electrolysis are ;

Water
 Hydrogen which is an extremely volatile gas open to furious burning in oxygen
Oxygen gas which is a great oxydiser
Electricity which is extremly sparky and hot, great for igniting fuel air gas mixtures. From the electrodes, from the static and perhaps ionisation.
Salts in the water to aid the electrolysis

This sounds to me like a good approximation of a bomb. How is it achieved safely at industrial levels.

[Origin]

This sounds to me like a good approximation of a bomb. How is it achieved safely at industrial levels.

We've been doing it safely for years.  On the sub I was on 40 years ago the oxygen I was breathing was made using electrolysis by the Oxygen Generator that was on board the sub.  By the way the Oxygen Generator was colloquially known as the bomb.

[paul cotter]

Stainless steel electrodes with a strongly basic electrolyte of sodium or potassium hydroxide(neutral or acidic conditions lead to corrosion unless one is using platinum electrodes) and apply a couple of volts dc and you are good to go. Hydrogen is released at the cathode(-) and oxygen at the anode(+).

[alancalverd]

Since the gases are evolved in two different places, there's never a problem keeping them apart. Electrode corrosion is a pain but lead-acid batteries last for many years.

The whole point of the exercise is, after all, to make an inflammable gas. You might a well complain that nitroglycerine is unstable and shouldn't be used as an explosive!

You can minimise all the problems by using AC electrolysis to produce "Brown's Gas" - a stoichiometric mix of H and O that burns quietly and can be used for welding under water or to drive a vehicle in a vacuum!

[paul cotter]

Virtually no corrosion with a basic electrolyte and stainless steel electrodes. Yes one can use ac and get a mix of gases but then one is dealing with a dangerously explosive product at all stages. It is much safer to keep the gases separate until the last stage, ie a gas mixer prior to the combustion stage. There have been fatal accidents in the US with the mixed gases.

[Petrochemicals (OP)]

This sounds to me like a good approximation of a bomb. How is it achieved safely at industrial levels.

We've been doing it safely for years.  On the sub I was on 40 years ago the oxygen I was breathing was made using electrolysis by the Oxygen Generator that was on board the sub.  By the way the Oxygen Generator was colloquially known as the bomb.

I dont deny that it has been done safely at a small scale, every school chemistry class must have done it at least once. I bet though even a small malfunction would be disasterous on a sub.

Hydrogen is released at the cathode(-) and oxygen at the anode(+).

But surely if you are splitting a substance into gas this seperation is less than perfect. How can a liquid be split into gas quite so seperatley? Is it like a wet battery where the oxygen/hydrogen are absorbed into the salts, only to be liberated the at the other electrode?

The whole point of the exercise is, after all, to make an inflammable gas. You might a well complain that nitroglycerine is unstable and shouldn't be used as an explosive

Therein lies the problem

[alancalverd]

But surely if you are splitting a substance into gas this seperation is less than perfect. How can a liquid be split into gas quite so seperatley?

Electrolysis. The laws of physics and chemistry do not permit compromise.

Quote from: alancalverd on Today at 14:41:15
The whole point of the exercise is, after all, to make an inflammable gas. You might a well complain that nitroglycerine is unstable and shouldn't be used as an explosive
Therein lies the problem

and the solution. If you don't want an inflammable gas, don't make it. If you do, be careful how you handle it. Not sure if it is still the case, but hydrogen used to be the "heaviest" chemical of all, in terms of annual production and consumption. It accounted for 25% of all domestic and industrial heating for over 100 years.

[Origin]

I bet though even a small malfunction would be disasterous on a sub.

You would be right!
From the guardian article, https://www.theguardian.com/uk/2009/feb/11/arctic-oxygen-submarine-hms-tireless
At the opening of a six-week hearing, Coroner Derek Winter said the explosion of an oxygen generator and the resulting deaths of two young crewmen had been "traumatic and terrifying" for all on board HMS Tireless which was on a UK/US operation off Alaska in March 2007 when disaster struck.

[vhfpmr]

I recall a TV prog (might have been Open Uni, can't remember) about an industrial accident at a dockyard. They were working on a ship in dry dock using pneumatic power tools and couldn't connect them because the hose connectors were the wrong type. After changing the connectors they got on with the job, and noticed that their fags were burning unusually fast, but thought nothing of it. It wasn't until after the explosion that they found out that the reason the hoses wouldn't fit the unions was that they were connecting them to the oxygen supply instead of the compressed air.