If you use hydrogen sulfide as an electron donor, you end up liberating sulfur, not oxygen. Contrary to grandparent, in oxygenic photosynthesis, the oxygen doe

If you use hydrogen sulfide as an electron donor, you end up liberating sulfur, not oxygen. Contrary to grandparent, in oxygenic photosynthesis, the oxygen does come from splitting water. The resulting hydride used to "charge" an electron carrier: https://en.wikipedia.org/wiki/Photodissociation#Photolysis_in_photosynthesis https://en.wikipedia.org/wiki/Photodissociation#Photolysis_i... The CO2 gets fixed into carbohydrates. Some water is generated in that process, but no molecular oxygen.