Hydrogen generation from low-temperature water-rock reactions
Hydrogen generation from low-temperature water-rock reactions
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DOI：
10.1038/ngeo1825
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发表时间：
2013-06-01
影响因子：
18.3
通讯作者：
Templeton, A. S.
中科院分区：
文献类型：
--
作者：
Mayhew, L. E.;Ellison, E. T.;Templeton, A. S.
氢通常是在镁铁质和超镁铁质岩石的高温水化过程中产生的，这是由于矿物中还原铁的氧化。众所周知，热液氢可以维持海底喷口和陆地温泉系统中的微生物群落。然而，在150摄氏度以下的温度下，氢气生成的速率和机制受到的限制很少。因此，氢燃料生态系统在地下陆地和海洋含水层的存在和范围仍然不确定。在这里，我们报告了实验室实验的结果，在实验中，我们将地面超镁铁质和基性岩石和矿物（特别是橄榄岩、辉石、橄榄石和磁铁矿）与缺氧流体在55和100摄氏度下反应，并监测氢气产量。我们使用基于同步加速器的微x射线荧光和x射线吸收近边结构光谱来识别材料中铁的形态变化。我们报告了反应物中尖晶石相的存在与分子氢生成之间的强烈相关性-具有通式[M2+M23+]O-4和立方晶体结构的氧化矿物。我们还在尖晶石相表面发现了铁(III)-（水合）氧化物反应产物，表明铁氧化。我们认为尖晶石表面吸附的Fe（II）和水之间的电子转移促进了低温下分子氢的生成。我们认为，在海洋和陆地地壳的超镁质含水层中，这些局部的产氢点可能支持氢基微生物的生命。
Hydrogen is commonly produced during the high-temperature hydration of mafic and ultramafic rocks, owing to the oxidation of reduced iron present in the minerals. Hydrothermal hydrogen is known to sustain microbial communities in submarine vent and terrestrial hot-spring systems. However, the rates and mechanisms of hydrogen generation below temperatures of 150 degrees C are poorly constrained. As such, the existence and extent of hydrogen-fuelled ecosystems in subsurface terrestrial and oceanic aquifers has remained uncertain. Here, we report results from laboratory experiments in which we reacted ground ultramafic and mafic rocks and minerals-specifically peridotite, pyroxene, olivine and magnetite-with anoxic fluids at 55 and 100 degrees C, and monitored hydrogen gas production. We used synchrotron-based micro-X-ray fluorescence and X-ray absorption near-edge structure spectroscopy to identify changes in the speciation of iron in the materials. We report a strong correlation between molecular hydrogen generation and the presence of spinel phases-oxide minerals with the general formula [M2+M23+]O-4 and a cubic crystal structure-in the reactants. We also identify Fe(III)-(hydr)oxide reaction products localized on the surface of the spinel phases, indicative of iron oxidation. We propose that the transfer of electrons between Fe(II) and water adsorbed to the spinel surfaces promotes molecular hydrogen generation at low temperatures. We suggest that these localized sites of hydrogen generation in ultramafic aquifers in the oceanic and terrestrial crust could support hydrogen-based microbial life.