Anoxic photochemical oxidation of siderite generates molecular hydrogen and iron oxides

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Abstract

Photochemical reactions of minerals are underappreciated processes that can make or break chemical bonds. We report the photooxidation of siderite (FeCO3) by UV radiation to produce hydrogen gas and iron oxides via a two-photon reaction. The calculated quantum yield for the reaction suggests photooxidation of siderite would have been a significant source of molecular hydrogen for the first half of Earth's history. Further, experimental results indicate this abiotic, photochemical process may have led to the formation of iron oxides under anoxic conditions. The reaction would have continued through the Archean to at least the early phases of the Great Oxidation Event, and provided a mechanism for oxidizing the atmosphere through the loss of hydrogen to space, while simultaneously providing a key reductant for microbial metabolism. We propose that the photochemistry of Earth-abundant minerals with wide band gaps would have potentially played a critical role in shaping the biogeochemical evolution of early Earth.

Original languageEnglish (US)
Pages (from-to)10073-10077
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number25
DOIs
StatePublished - Jun 18 2013

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Astrobiology
  • Banded iron formations
  • Photogeochemistry.archean iron cycle

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