Plants like solar cells utilize intermittent non-point insolation to biologically fix CO₂ in the form of biomass carbohydrates. However, plant photosynthesis has pretty low solar energy-to-chemical energy conversion efficiencies (e.g., ~0.2-0.3%, global average) and consumes a large amount of water (i.e., at least 500 kg of water per kg of biomass generated). Such low energy efficiencies are mainly attributed to three factors: (i) a narrow light absorption spectrum by chlorophyll, (ii) relatively low efficiencies of carbohydrate synthesis and unmatched reaction rates between fast light-harvesting reactions and slow dark chemical synthesis reactions, and (iii) carbohydrate losses due to the respiration of living plants.

To surpass these limitations in plants, we design a novel scalable bioprocess integrating high-efficiency solar cells, water electrolysis, and biological CO₂ fixation mediated by cascade enzymes for the similar function. This synthetic enzymatic pathway containing in vitro numerous enzymes and coenzymes would fix CO₂ into carbohydrates (e.g. starch) and/or ethanol by using electricity or hydrogen. Such in vitro synthetic enzymatic pathways are believed to work based on the design principles of synthetic biology, knowledge in the literature, and thermodynamics analysis. However, validation experiments and practical application of these systems will require collaborative efforts from biologists, chemists, electrochemists, and engineers. Here we present our latest advances in the proof-of-concept experiment. Large-scale implementation of this artificial photosynthesis would address such sustainability challenges as electricity and hydrogen storage, CO₂ utilization, fresh water conservation, and maintenance of a small closed ecosystem for human survival in emergency situations.