(Invited) Solar-Driven Electrochemical Conversion of Carbon Dioxide to Hydrocarbons and Oxygenates

Wednesday, 4 October 2017: 14:40
National Harbor 6 (Gaylord National Resort and Convention Center)
J. W. Ager III (Lawrence Berkeley National Laboratory, Joint Center for Artificial Photosynthesis)
Sustainable solar to fuel conversion could provide an alternative to mankind’s currently unsustainable use of fossil fuels [1]. Solar fuel generation by photoelectrochemical (PEC) and electrochemical methods is a potentially promising approach to address this fundamental challenge. To date, solar to fuel research efforts have been mostly focused on solar water splitting, which produces hydrogen [2]. In contrast, the conversion of CO2 to hydrocarbons that could displace currently used fossil fuels is considerably less well developed [3].

Achieving a viable solar-driven EC CO2 reduction energy conversion efficiency requires minimizing potential losses in all aspects of the device including the cathode, anode, electrolyte, and membrane. Achieving selective products requires management of multi-electron transfer reactions [4]. Strategies to optimize each component (anode, cathode, electrolyte, cell design) of our CO2 electrolyzer cell to obtain high selectivity and energy conversion efficiency at low overpotential will be described. An overall cell design which has efficient gas to liquid mass transfer of CO2 is employed [5]. Use of a CsHCO3 buffered electrolyte increases selectivity to C2+ products such as ethylene and ethanol [6]. A nanostructured anode is used which shows superior stability and high performance for oxygen evolution in the pH range of interest for CO2 reduction. Finally, a cathode design has been developed which enables selectivity to hydrocarbons and oxygenates over a wide range of pH and cell voltage conditions.

Solar-driven CO2 reduction is accomplished by coupling the optimized electrolysis device to solar cells. 1 sun efficiencies of over 4% for the production of hydrocarbons and oxygenates are achieved. Notably, the overall system also functions at >1% conversion efficiency at illumination intensities down to 0.3 suns.

  1. Chu, S.; Cui, Y.; Liu, N. The Path towards Sustainable Energy. Nat. Mater. 2016, 16, 16–22.
  2. Ager, J. W.; Shaner, M. R.; Walczak, K. A.; Sharp, I. D.; Ardo, S. Experimental Demonstrations of Spontaneous, Solar-Driven Photoelectrochemical Water Splitting. Energy Environ. Sci. 2015, 8, 2811–2824.
  3. Goeppert, A.; Czaun, M.; Jones, J.-P.; Surya Prakash, G. K.; Olah, G. A. Recycling of Carbon Dioxide to Methanol and Derived Products – Closing the Loop. Chem. Soc. Rev. 2014, 43, 7995–8048.
  4. Y. Hori, in Mod. Asp. Electrochem., (Springer New York, New York, NY, 2008), pp. 89–189.
  5. Lobaccaro, P.; Singh, M. R.; Clark, E. L.; Kwon, Y.; Bell, A. T.; Ager, J. W. Effects of Temperature and Gas–liquid Mass Transfer on the Operation of Small Electrochemical Cells for the Quantitative Evaluation of CO 2 Reduction Electrocatalysts. Phys. Chem. Chem. Phys. 2016, 18, 26777–26785.
  6. Singh, M. R.; Kwon, Y.; Lum, Y.; Ager, J. W.; Bell, A. T. Hydrolysis of Electrolyte Cations Enhances the Electrochemical Reduction of CO2 over Ag and Cu. J. Am. Chem. Soc. 2016, 138, 13006–13012.