Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
Proc Natl Acad Sci U S A. 2013 Jun 18;110(25):10073-7. doi: 10.1073/pnas.1308958110. Epub 2013 Jun 3.
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.
矿物的光化学反应是被低估的过程，它可以形成或破坏化学键。我们报告了通过紫外线辐射将菱铁矿（FeCO3）光氧化为氢气和氧化铁的两光子反应。反应的计算量子产率表明，在地球历史的前半段，菱铁矿的光氧化将是分子氢的重要来源。此外，实验结果表明，这种非生物的光化学过程可能导致缺氧条件下氧化铁的形成。该反应将持续到太古代，至少在大氧化事件的早期阶段，并提供了一种通过向太空损失氢气来氧化大气的机制，同时为微生物代谢提供了一种关键的还原剂。我们提出，具有宽能带隙的地球丰富矿物质的光化学可能在塑造早期地球的生物地球化学演化方面发挥了关键作用。
