Electrochemical CO2 Reduction by Ni-containing Iron Sulfides: How Is CO2 Electrochemically Reduced at Bisulfide-Bearing Deep-sea Hydrothermal Precipitates?
Electrochemical CO2 Reduction by Ni-containing Iron Sulfides: How Is CO2 Electrochemically Reduced at Bisulfide-Bearing Deep-sea Hydrothermal Precipitates?
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DOI：
10.1016/j.electacta.2014.07.078
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发表时间：
2014-09
影响因子：
6.6
通讯作者：
A. Yamaguchi;M. Yamamoto;K. Takai;Takumi Ishii;K. Hashimoto;Ryuhei Nakamura
中科院分区：
文献类型：
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作者：
A. Yamaguchi;M. Yamamoto;K. Takai;Takumi Ishii;K. Hashimoto;Ryuhei Nakamura
20世纪70年代末S发现的深海热液喷口，引发了许多关于生前海洋化学演化和古代地球能量代谢早期演化的假说。这类研究的立足点是寻求生物能量进化，利用氢等还原化学物质进行二氧化碳还原和碳同化。除了H_2和CO_2的直接反应外，通过含二硫化物的烟囱结构的电流还指向在寒冷的海洋-喷口界面上可能发生的电催化CO_2还原(R.Nakamura等人。化学。内部艾德2010年，49,7692(−(7694))。为了证实这一假设的正确性，我们在这里考察了在弱酸性pH条件下，硫化铁(FeS)沉淀物电催化还原二氧化碳的能量学。虽然FeS沉积不能有效地还原CO2，但通过用Ni取代Fe生成FeNi2S4(紫晶石)，并用胺类化合物进一步修饰其表面，大大提高了反应效率。CO2还原的电位依赖活性表明，热液中的H2还原CO2参与了强烈的电子传递反应，这表明热液烟囱壁上将建立高达200 mV的自然产生的质子动力(PMF)。然而，在烟囱结构中，H2的生成与CO2的还原竞争电流，导致PMF的快速消耗。因此，为了维持热液喷发矿床的PMF和有机化合物的电合成，我们提出了一种FeS矿床的动态平衡pH调节机制，即利用热液矿床中储存的元素氢来平衡生成H_2对电化学梯度的消耗。
The discovery of deep-sea hydrothermal vents on the late 1970's has led to many hypotheses concerning chemical evolution in the prebiotic ocean and the early evolution of energy metabolism in ancient Earth. Such studies stand on the quest for the bioenergetic evolution to utilize reducing chemicals such as H2for CO2reduction and carbon assimilation. In addition to the direct reaction of H2and CO2, the electrical current passing across a bisulfide-bearing chimney structure has pointed to the possible electrocatalytic CO2reduction at the cold ocean-vent interface (R. Nakamura, et al.Angew. Chem. Int. Ed. 2010, 49, 7692 − 7694). To confirm the validity of this hypothesis, here, we examined the energetics of electrocatalytic CO2reduction by iron sulfide (FeS) deposits at slightly acidic pH. Although FeS deposits inefficiently reduced CO2, the efficiency of the reaction was substantially improved by the substitution of Fe with Ni to form FeNi2S4(violarite), of which surface was further modified with amine compounds. The potential-dependent activity of CO2reduction demonstrated that CO2reduction by H2in hydrothermal fluids was involved in a strong endergonic electron transfer reaction, suggesting that a naturally occurring proton-motive force (PMF) as high as 200 mV would be established across the hydrothermal vent chimney wall. However, in the chimney structures, H2generation competes with CO2reduction for electrical current, resulting in rapid consumption of the PMF. Therefore, to maintain the PMF and the electrosynthesis of organic compounds in hydrothermal vent mineral deposits, we propose a homeostatic pH regulation mechanism of FeS deposits, in which elemental hydrogen stored in the hydrothermal mineral deposits is used to balance the consumption of the electrochemical gradient by H2generation.