(454b) Efficiency Limits of an Integrated Solar-Driven CO2 Capture and Reduction Systems

One of the grand challenges of the 21^st century is the abatement of rising concentration of CO₂ in the atmosphere. The anthropogenic contribution of CO₂ from sources like power plants and chemical industries has led to the rise in CO₂ concentration at the rate of ~1.8 ppm per year in the atmosphere severely affecting the earth’s climate. There is a dire need to develop efficient technologies for integrated CO₂ capture and reduction to sustainably produce carbon-neutral or carbon-negative fuels. Artificial photosynthesis is one of the promising techniques that utilizes solar energy and H₂O to reduce CO₂ into fuels. However, the integration of a suitable CO₂ capture technique with the artificial photosynthetic system has not been evaluated or implemented. Here, we show the thermodynamic and realistic efficiencies of an integrated system that captures CO₂ from air/flue gas and simultaneously reduces it to produce carbon-neutral fuels using solar energy. Effectiveness and compatibility of various carbon capture technique such as an ideal process, adsorption, membrane separation, absorption, and electrodialysis in an integrated system have been evaluated using a real triple junction light absorber and ideal light absorbers of varying junctions (1 to 10) and band-gaps. The overall solar-to-fuel (STF) efficiencies for the CO₂ reduction products for the ideal multijunction light absorbers are in the range of 19-27% for single junction, 34-40% for double junction, and 24-34% for triple junction ideal light absorber. For the real triple junction light absorber, membrane separation coupled with CO₂ reduction was found to be the best configuration of an integrated system.