I will transcribe this from a chemical engineering journal*1) for my own understanding. Let's consider the reaction of a plant that reduces CO2 to oxygen. First, a water molecule is "photo-oxidized" to produce one mole of oxygen molecules, and at the same time, two moles of "hydride" (H-) are produced, and these two moles of "hydride" reduce CO2. In short, the equation for the photo-oxidation of water is ② from ①. H- = H+ + 2e- ① 2H2O+4hν → O2+4e- + 4H+ → O2+2H- + 2H+ ② The "conversion of photons (hν) to electron energy (e-)" in equation ① above is achieved by the catalytic function of chlorophyll in plants. Artificially, it is done by photocatalysts. The author of this article has succeeded in "CO2 reduction to methanol" *2). The principle is the reduction of CO2 by 3 moles of "hydride" ③. 3H- + CO2 + 3H+ → CH3-OH (methanol) + H2O ③ *1)Production Engineering Journal, Chemical Equipment, April 2021, p63 *2)Y. Mats...