What’s the theoretical limit of heat -> electricity + hydrolysis? It seems if we could capture electricity from a space shuttle reentry and make hydrogen/metha

What’s the theoretical limit of heat -> electricity + hydrolysis? It seems if we could capture electricity from a space shuttle reentry and make hydrogen/methane during descent, this would enable less energy intensive launches. I’d imagine this would be done if it were possible, but the extreme burst of energy likely isn’t conducive to being absorbed by hydrolysis.