Electrolysis cannot hit 100% efficiency. Maybe the approximate math can, if you only consider the first law of thermodynamics, but you’ll violate the second the moment it enters reality.

Alkaline electrolysis maxes out at 66% theoretically. PEM is maybe 80% but that’s neglecting system-level losses.

You cannot extract energy from compressed gas if your fuel cell requires gas at that pressure in order to operate.

There is this weird cult of first principles I keep encountering where people think they’ve cracked the code but they just don’t understand systems.

You are completely wrong. You are not thinking of the laws of thermodynamics. You are thinking of Carnot’s theorem. Which doesn’t apply because electrolyzers are not heat engines. They are electrochemical systems, just like li-ion batteries. What you’re writing is just pseudoscience.

The theoretical limit of both alkaline and PEM electrolysis efficiency is 100%. Real world is somewhat less, but you can get to something like 98% even in the real world: https://www.inceptivemind.com/hysatas-record-breaking-electr...

Fuel cells do not operate at 700 bars of pressure. There is definitely a possibility of extracting energy from compressed gases.

Sorry, but you are spouting total bullshit on all levels here. The only cult is whatever battery/electrification fanbase you’re a part of. You are just repeating BEV propaganda designed to shut down critical thinking and defame all alternative ideas. If anything, this type of tactic is a good sign that we are witnessing the end of the BEV, mainly because its advocates must resort to blatant lies to promote it.