Artificial photosynthesis steps up

Photosynthesis fixes CO₂ from the air by using sunlight. Industrial mimics of photosynthesis seek to convert CO₂ directly into biomass, fuels, or other useful products. Improving on a previous artificial photosynthesis design, Liu et al. combined the hydrogen-oxidizing bacterium Raistonia eutropha with a cobalt-phosphorus water-splitting catalyst. This biocompatible self-healing electrode circumvented the toxicity challenges of previous designs and allowed it to operate aerobically. When combined with solar photovoltaic cells, solar-to-chemical conversion rates should become nearly an order of magnitude more efficient than natural photosynthesis.

Abstract

Artificial photosynthetic systems can store solar energy and chemically reduce CO₂. We developed a hybrid water splitting–biosynthetic system based on a biocompatible Earth-abundant inorganic catalyst system to split water into molecular hydrogen and oxygen (H₂ and O₂) at low driving voltages. When grown in contact with these catalysts, Ralstonia eutropha consumed the produced H₂ to synthesize biomass and fuels or chemical products from low CO₂ concentration in the presence of O₂. This scalable system has a CO₂ reduction energy efficiency of ~50% when producing bacterial biomass and liquid fusel alcohols, scrubbing 180 grams of CO₂ per kilowatt-hour of electricity. Coupling this hybrid device to existing photovoltaic systems would yield a CO₂ reduction energy efficiency of ~10%, exceeding that of natural photosynthetic systems.

http://science.sciencemag.org/content/352/6290/1210