Photoautotrophs use photoautotrophs use h2s as an energy source and co2 as a carbon source n2 as an energy source and co2 as a carbon source light as an energy source and methane as a carbon source

Photoautotrophs use light as an energy source and CO₂ as a carbon source .

Photoautotrophs use light as an energy source and organic carbon as a carbon source that organic carbon can be  alcohol, fatty acid , organic acid and carbohydrates as Photoautotrophs does not use water to reduce CO₂, they do not produce oxygen that is O₂ as byproduct of metabolism.

if you mean hydrogen and oxygen then water is the product