University of Hertfordshire

Documents

  • Rafaela Vasiliadou
  • Nikolay Dimov
  • Nicolas Szita
  • Sean F. Jordan
  • Nick Lane
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Original languageEnglish
JournalInterface Focus
Journal publication date22 Aug 2019
Publication statusAccepted/In press - 22 Aug 2019

Abstract

Methanogens are putatively ancestral autotrophs that reduce CO2 with H2 to form biomass using a membrane-bound, proton-motive Fe(Ni)S protein called the Energy-converting hydrogenase (Ech). At the origin of life, geologically sustained H+ gradients across inorganic barriers containing Fe(Ni)S minerals could theoretically have driven CO2 reduction by H2 through vectorial chemistry in a similar way to Ech. pH modulation of the redox potentials of H2, CO2 and Fe(Ni)S minerals could in principleenable an otherwise endergonic reaction. Here we analyse whether vectorial electrochemistry can facilitate the reduction of CO2 by H2 under alkaline hydrothermal conditions using a microfluidic reactor. We present pilot data showing that steep pH gradients of ~5 pH units can be sustained over >5 hours across Fe(Ni)S barriers, with H+-flux across the barrier about 2-million-fold faster than OH-flux. This high flux produces a calculated 3-pH unit-gradient (equating to 180 mV) across single ~25-nm Fe(Ni)S nanocrystals, which is close to that required to reduce CO2. However, the poor solubility of H2 at atmospheric pressure limits CO2 reduction by H2, explaining why organic synthesis has so far proved elusive in our reactor. Higher H2 concentration will be needed in future to facilitate COreduction through prebiotic vectorial electrochemistry.

Notes

The attached manuscript has been peer-reviewed and accepted, however it is not available on the journal web page.

ID: 17332968