Extracellular Electron Transfer Across Bio-Nano Interfaces for CO2 Electroreduction

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Acetogenic bacteria represent a class of organisms capable of converting reducing equivalents and carbon dioxide into products with carbon-carbon bonds. Materials-based bio-electrochemical approaches are attractive for supplying biological organisms directly with grid-supplied electrons to convert carbon dioxide to value-added chemicals. Carbon nanotube-modified biocathodes have emerged as promising candidates for microbial electrosynthesis with high yields of carbon product formation, but a fundamental understanding of extracellular charge transfer at this electrode-biofilm interface is still lacking. Here, we utilize solid-state interfaces between semiconducting single-walled carbon nanotubes (s-SWCNT) and a model acetogenic bacterium for mechanistic studies of electro-catalytic CO2 conversion to acetate. Studies of bacteria/s-SWCNT interactions in a transistor-based device suggest direct extracellular electron transfer (EET) at the bio-nano interface. Deuterium isotope labeling experiments confirmed that the availability of electrochemically produced H2 as a redox mediator does not limit the efficiency of EET and CO2 electro-reduction for C. ljungdahlii biofilms, suggesting the primary reducing equivalents are the electrons delivered across the electrode/bacterium interface or involvement of biological redox mediators. Additional isotope labeling studies demonstrate high Faradaic efficiency for CO2 electro-reduction at the SWCNT/bacterium interface. These results provide important information about EET across the bacterium/material interface in a model biocathode.

Original languageAmerican English
Pages (from-to)1093-1102
Number of pages10
Issue number2
StatePublished - 14 Jan 2021

Bibliographical note

Publisher Copyright:
© The Royal Society of Chemistry.

NREL Publication Number

  • NREL/JA-2700-78890


  • electrocatalysis
  • semiconducting single-walled carbon nanotubes
  • solid-state interfaces


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