Methane Photosynthesis

[Vaktus]

This would be useful for sky-plankton in the atmosphere of a gas giant. I imagine skyplanton cells to look like bubbles of pure hydrogen, using the tiny density difference between hydrogen and helium to stay afloat. It would be very useful if the photosynthesis process used (or produced hydrogen) as a major component.

Perhaps this reaction would be better?

CO2(aq) + 4 H2(aq)→CH4(aq) + 2 H2O(aq)

though, this reaction produces less energy the colder the environment is and lesser the CO2 is in the atmosphere.