Bacteria–photocatalyst sheet for sustainable carbon dioxide utilization

The clean conversion of carbon dioxide and water to a single multicarbon product and O2 using sunlight via photocatalysis without the assistance of organic additives or electricity remains an unresolved challenge. Here we report a bio-abiotic hybrid system with the non-photosynthetic, CO2-fixing acetogenic bacterium Sporomusa ovata grown on a scalable and cost-effective photocatalyst sheet consisting of a pair of particulate semiconductors (La and Rh co-doped SrTiO3 (SrTiO3:La,Rh) and Mo-doped BiVO4 (BiVO4:Mo)). The biohybrid effectively produces acetate (CH3COO–) and oxygen (O2) using only sunlight, CO2 and H2O, achieving a solar-to-acetate conversion efficiency of 0.7% at ambient conditions (298 K, 1 atm). The photocatalyst sheet oxidizes water to O2 and provides electrons and hydrogen (H2) to S. ovata for the selective synthesis of CH3COO– from CO2. To demonstrate utility in a closed carbon cycle, the solar-generated acetate was used directly as feedstock in a bioelectrochemical system for electricity generation. These semi-biological approaches thus offer a promising strategy for sustainably and cleanly fixing CO2 and closing the carbon cycle. Conversion of CO2 to fuels or chemicals via artificial photosynthesis usually requires the assistance of organic additives or electricity. Now, a biohybrid system is reported consisting of a photocatalyst sheet and bacteria producing acetate and O2 from CO2 and H2O using sunlight as the sole energy input.