Solar-powered electrochemical reduction of CO2 and H2O to syngas, followed by fermentation, could lead to sustainable production of useful chemicals. However, due to insufficient electric current densities and instabilities of current CO2-to-CO electrolysers, a practical, scalable artificial photosynthesis remains a major challenge. Here, we address these problems using a commercially available silver-based gas diffusion electrode (used in industrial-scale chlorine–alkaline electrolysis) as the cathode in the CO2 electrolyser. Electric current densities up to 300 mA cm–2 were demonstrated for more than 1,200 hours with continuous operation. This CO2 electrolyser was coupled to a fermentation module, where the out-coming syngas from the CO2 electrolyser was converted to butanol and hexanol with high carbon selectivity. Conversion of photovoltaic electricity, CO2 and H2O to the desired alcohols achieved close to 100% Faradaic efficiency. Industrial production of useful and high-value chemicals via artificial photosynthesis is closer than expected with the proposed scalable hybrid system.
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The authors thank R. K. Thauer (Max Planck Institute for Terrestrial Microbiology, Marburg) for his help in preparing the manuscript. Evonik Creavis GmbH (T.H. and M.D.), Siemens AG (R.K. and G.S.) and Covestro AG (R.W.) thank the German Federal Ministry of Education and Research (BMBF) for funding part of this work within the Kopernikus Initiative ‘Power-to-X’ under contract number P2X-03SFK2J0.
Supplementary Figs. 1–4 and Supplementary Table 1
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