Artificial photosynthesis systems and methods for producing carbon-based chemical compounds

This disclosure provides systems, methods, and apparatus related to artificial photosynthesis. In one aspect a system includes a photoanode chamber including a photoanode assembly, a photocathode chamber including a photocathode assembly, an electrical connection electrically connecting the photoanode assembly and the photocathode assembly, a membrane separating the photoanode chamber and the photocathode chamber, and a microorganism disposed in the photocathode chamber. The photoanode assembly is operable to oxidize water to generate oxygen, protons, and electrons. The membrane is permeable to the protons and operable to allow the protons to travel to the photocathode chamber. The electrical connection provides electrons to the photocathode assembly. The microorganism comprises a metabolic pathway to reduce carbon dioxide and to generate a carbon-based compound using the electrons or hydrogen formed by two protons.