I Does pressure affect the thermal breakdown of water?

AI Thread Summary
Thermal breakdown (thermolysis) of water requires approximately 3000°C, and pressure significantly influences this process. Increased pressure shifts the equilibrium back toward water formation, complicating the thermolysis. The relationship between pressure and temperature can be analyzed using Gibbs free energy, where higher pressure raises the thermolysis temperature despite unchanged heat components. Real-world inefficiencies in pumps mean that high-pressure thermolysis demands more energy than ambient conditions. Additionally, maintaining the separation of hydrogen and oxygen gases is likely easier at lower pressures.
some bloke
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As per the title, I'm trying to research how the thermal breakdown (thermolysis) of water works. I gather that you need circa 3000°C to get it to break down, which is a lot, and I'm curious as to how pressure might affect this.

I know that pressure affects the boiling point of water, and as such was concerned that a theoretical device which compresses superheated steam to increase it's temperature might counteract the desired effects of thermolysis by the increase of pressure making the required temperature for thermolysis higher.

I'd appreciate any reading that people can direct me to on this subject, I am contemplating a combination of heat, pressure and electrolysis for breaking down water into hydrogen and oxygen. I don't want to make the mistake of only considering the energy in this!
 
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some bloke said:
Summary: see title

As per the title, I'm trying to research how the thermal breakdown (thermolysis) of water works. I gather that you need circa 3000°C to get it to break down, which is a lot, and I'm curious as to how pressure might affect this.
Qualitatively, the Le Chatelier`s principle is applicable here. Thermolizing water increase pressure (two water molecules split into one molecule of oxygen and two of hydrogen), therefore increased pressure shift equilibrum back to formation of water.
some bloke said:
I'd appreciate any reading that people can direct me to on this subject, I am contemplating a combination of heat, pressure and electrolysis for breaking down water into hydrogen and oxygen. I don't want to make the mistake of only considering the energy in this!
In detail, effect of pressure is affecting the entropy component ΔS of Gibbs energy , while heat component ΔH is unchanged. Therefore, with increased pressure, your energy expended to reach desired decomposition yield should not change if pump is 100% efficient, but termolizis temperature will increase. To calculate temperature of 50% thermolysis yield, your should solve Gibbs free energy equation ΔH-TΔS=0.

Of course, in real world 100% efficient pumps do not exist, therefore high pressure thermolysis of water will require more energy compared to ambient pressure thermolysis.
 
some bloke said:
Summary: see title

I gather that you need circa 3000°C to get it to break down, which is a lot, and I'm curious as to how pressure might affect this.
How do you separate, and then maintain separation, of the O2 and H2 gas? I would expect that to be easier at low pressure, rather than very high pressure.

Maybe you should look at the ultrasonic resonant cavitation experiments that reach temperatures between 10,000 K and 20,000 K.
https://en.wikipedia.org/wiki/Sonoluminescence
 

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