University of Hertfordshire

Documents

  • Rafaela Vasiliadou
  • Nikolay Dimov
  • Nicolas Szita
  • Sean F. Jordan
  • Nick Lane
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Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalInterface Focus
Volume9
Issue6
DOIs
Publication statusPublished - 18 Oct 2019

Abstract

Methanogens are putatively ancestral autotrophs that reduce CO 2 with H 2 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 CO 2 reduction by H 2 through vectorial chemistry in a similar way to Ech. pH modulation of the redox potentials of H 2, CO 2 and Fe(Ni)S minerals could in principle enable an otherwise endergonic reaction. Here, we analysewhether vectorial electrochemistry can facilitate the reduction of CO 2 by H 2 under alkaline hydrothermal conditions using a microfluidic reactor. We present pilot data showing that steep pH gradients of approximately 5 pH units can be sustained over greater than 5 h across Fe(Ni)S barriers, with H+-flux across the barrier about two million-fold faster than OH-flux. This high flux produces a calculated 3-pH unit-gradient (equating to 180 mV) across single approximately 25-nm Fe(Ni)S nanocrystals, which is close to that required to reduce CO 2. However, the poor solubility of H2 at atmospheric pressure limits CO 2 reduction by H 2, explaining why organic synthesis has so far proved elusive in our reactor. Higher H 2 concentration will be needed in future to facilitate CO 2 reduction through prebiotic vectorial electrochemistry.

Notes

© 2019 The Authors.Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.

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