Water splitting–biosynthetic system with CO ₂ reduction efficiencies exceeding photosynthesis

TLDR

Artificial photosynthetic systems can store solar energy and chemically reduce CO₂. The study develops a hybrid water‑splitting–biosynthetic system that splits water into hydrogen and oxygen at low driving voltages. The system employs a biocompatible Earth‑abundant inorganic catalyst to achieve water splitting, and Ralstonia eutropha consumes the produced H₂ to convert low‑concentration CO₂ into biomass and fuels in the presence of O₂. The system attains a CO₂ reduction energy efficiency of ~50 % for biomass and fusel alcohol production, scrubbing 180 g CO₂ kWh⁻¹, and could reach ~10 % efficiency when coupled to photovoltaics, surpassing 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.