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CO2 reduction driven by a pH gradient.

Abstract：

:All life on Earth is built of organic molecules, so the primordial sources of reduced carbon remain a major open question in studies of the origin of life. A variant of the alkaline-hydrothermal-vent theory for life's emergence suggests that organics could have been produced by the reduction of CO2 via H2 oxidation, facilitated by geologically sustained pH gradients. The process would be an abiotic analog-and proposed evolutionary predecessor-of the Wood-Ljungdahl acetyl-CoA pathway of modern archaea and bacteria. The first energetic bottleneck of the pathway involves the endergonic reduction of CO2 with H2 to formate (HCOO-), which has proven elusive in mild abiotic settings. Here we show the reduction of CO2 with H2 at room temperature under moderate pressures (1.5 bar), driven by microfluidic pH gradients across inorganic Fe(Ni)S precipitates. Isotopic labeling with 13C confirmed formate production. Separately, deuterium (2H) labeling indicated that electron transfer to CO2 does not occur via direct hydrogenation with H2 but instead, freshly deposited Fe(Ni)S precipitates appear to facilitate electron transfer in an electrochemical-cell mechanism with two distinct half-reactions. Decreasing the pH gradient significantly, removing H2, or eliminating the precipitate yielded no detectable product. Our work demonstrates the feasibility of spatially separated yet electrically coupled geochemical reactions as drivers of otherwise endergonic processes. Beyond corroborating the ability of early-Earth alkaline hydrothermal systems to couple carbon reduction to hydrogen oxidation through biologically relevant mechanisms, these results may also be of significance for industrial and environmental applications, where other redox reactions could be facilitated using similarly mild approaches.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Hudson R,de Graaf R,Strandoo Rodin M,Ohno A,Lane N,McGlynn SE,Yamada YMA,Nakamura R,Barge LM,Braun D,Sojo V

doi

10.1073/pnas.2002659117

subject

Has Abstract

pub_date

2020-09-15 00:00:00

pages

22873-22879

issue

eissn

0027-8424

issn

1091-6490

pii

2002659117

journal_volume

117

pub_type

杂志文章

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CO2 reduction driven by a pH gradient.