The solar-driven electrochemical reduction of CO2 to fuels and chemicals provides a promising way for closing the anthropogenic carbon cycle. However, the lack of selective and Earth-abundant catalysts able to achieve the desired transformation reactions in an aqueous matrix presents a substantial impediment as of today. Here we introduce atomic layer deposition of SnO2 on CuO nanowires as a means for changing the wide product distribution of CuO-derived CO2 reduction electrocatalysts to yield predominantly CO. The activity of this catalyst towards oxygen evolution enables us to use it both as the cathode and anode for complete CO2 electrolysis. In the resulting device, the electrodes are separated by a bipolar membrane, allowing each half-reaction to run in its optimal electrolyte environment. Using a GaInP/GaInAs/Ge photovoltaic we achieve the solar-driven splitting of CO2 into CO and oxygen with a bifunctional, sustainable and all Earth-abundant system at an efficiency of 13.4%.

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The authors acknowledge L. Pan for experimental help during revision, K. V. Thomas and S. Coudret for ICP-MS analysis, P. Mettraux for XPS analysis, M. Söderlund and H. Tholense (Beneq, Finland) for FBR-ALD depositions and D. Alexander for aberration-corrected STEM data. This work was funded by Siemens AG, and M.S. and M.G. would like to express their particular gratitude to Siemens AG for continued support. J.L. acknowledges the Marie Skłodowska-Curie Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 291771 for financial support.

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  1. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland

    • Marcel Schreier
    • , Ludmilla Steier
    • , Matthew T. Mayer
    • , Jingshan Luo
    •  & Michael Grätzel
  2. Laboratory of Sustainable and Catalytic Processing, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland

    • Florent Héroguel
    •  & Jeremy S. Luterbacher
  3. Abengoa Research, Abengoa, c/Energía Solar n 1, Campus Palmas, Altas, 41014 Sevilla, Spain

    • Shahzada Ahmad


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M.S. designed the project, prepared samples, conducted experiments, analysed the data and wrote the manuscript. J.L. designed and supervised the project, and contributed to experiments, writing of the manuscript and data analysis. F.H. conducted chemisorption and TPD measurements and analysed the relevant data. L.S. assisted with ALD deposition of SnO2. J.S.L. assisted with chemisorption and TPD analysis and corrected the manuscript. M.T.M. contributed to writing the manuscript. S.A. provided the three-junction solar cells and had the idea for its use in this application. M.G. supervised the project, directed the research and established the final version of the manuscript. All authors commented on the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Jingshan Luo or Michael Grätzel.

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