Natural solar cells and their geochemical implications

天然太阳能电池及其地球化学意义

• 批准号: 1148494
• 负责人: Carrick Eggleston
• 金额: $ 14.08万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-15 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1148494&HistoricalAwards=false
• 关键词: Natural; solar; cells; their; geochemical

Technical description:The role of photoelectrochemical processes in Earth?s early history is not well understood. Many common oxide and sulfide minerals are photoactive and capable of driving natural photoredox processes. The proposal discusses several major events in Earth history, such as banded iron formations and the rise of oxygen, to which such photochemically active minerals might have contributed. The project focuses in particular on a new concept in natural photoelectrochemistry: coupled-mineral systems.In solar energy research, there is a great deal of interest in photochemical water splitting ? the formation of O2 and H2 using sunlight and water. Such processes are usually quite inefficient, but engineered ?tandem cells? have been constructed in which two semiconductors, each absorbing a different light wavelength, greatly improve the efficiency of the overall photocatalytic process. The photochemical current densities that we measured in initial experiments with hematite-pyrite tandem cell (which can be expected to form in nature as the simple consequence of incipient pyrite oxidation) are surprisingly comparable to the deposition rates of iron in banded iron formations and the rate of water loss from Mars over time. The time seems ripe, therefore, to study a few likely naturally-occurring mineral tandem cell systems in order to quantify the extent to which mineral-based photochemistry might have driven important early-Earth and planetary processes.We propose to investigate the behavior and properties of such natural photo-electrochemical cells. We intend to understand the rates at which water can be oxidized and hydrogen produced, the rates at which other common aqueous solutes can be oxidized or reduced, the mineral properties needed for such processes, assess a small set of mineral systems that could have been important on early Earth, and investigate the effects of variable pO2, light intensity, pH, temperature, and both aqueous and solid compositions on the overall photoelectrochemical process. Non-technical explanation:While the role of semiconducting minerals in natural processes of the Earth is of geological interest, the fundamental properties of mineral semiconductors as photocatalysts are probably of greatest significance in the development of solar energy technology. If a solar photocatalytic system can be developed that produces fuels (chemically stored energy) reasonably efficiently, such technology ? if it is to truly impact the global energy picture in the long run ? must be constructed of Earth-abundant materials. Iron and manganese oxides and sulfides are common, whereas there is simply not enough platinum on Earth to be used as electrodes/catalyst for such systems. From the point of view of medium- to long-term energy security (not to mention climate change), such fuel-generating technologies as described in this proposal need to be better studied, improved, and implemented. The PI has experience both in fundamental geochemistry research as well as with scientists working on solar energy, and the improved understanding of the tandem-cell mineral systems in this proposal has applications equally in geochemistry and solar energy technology.

技术说明：光电化学过程在地球中的作用？的早期历史还不太清楚。 许多常见的氧化物和硫化物矿物是光活性的，能够驱动自然光氧化还原过程。 该提案讨论了地球历史上的几个重大事件，例如带状铁的形成和氧气的上升，这些光化学活性矿物可能对此做出了贡献。 该项目特别关注自然光电化学的一个新概念：耦合矿物系统。利用阳光和水形成氧气和氢气。 这些过程通常效率很低，但经过设计？串联电池？已经构建了两种半导体，每种半导体吸收不同的光波长，大大提高了整个光催化过程的效率。 我们在最初的实验中测量到的光化学电流密度与赤铁矿-黄铁矿串联电池（可以预期在自然界中形成的初始黄铁矿氧化的简单结果）令人惊讶地与带状铁地层中铁的沉积速率和火星随时间推移的水损失速率相当。 因此，研究一些可能自然发生的矿物串联电池系统的时机似乎已经成熟，以便量化矿物光化学可能在多大程度上驱动了重要的早期地球和行星processes.We建议调查这种天然光电化学电池的行为和特性。 我们打算了解水可以被氧化和产生氢的速率，其他常见的水溶性溶质可以被氧化或还原的速率，这些过程所需的矿物特性，评估一小部分可能在早期地球上很重要的矿物系统，并研究可变pO 2，光照强度，pH值，温度，以及含水和固体组合物对整个光电化学过程的影响。 非技术性解释：虽然半导体矿物在地球自然过程中的作用具有地质意义，但矿物半导体作为光催化剂的基本特性可能对太阳能技术的发展具有最重要的意义。 如果太阳能光催化系统可以开发，生产燃料（化学储存能量）合理有效，这种技术？从长远来看，它是否真的会影响全球能源状况？必须用地球上丰富的材料建造 铁和锰的氧化物和硫化物很常见，而地球上根本没有足够的铂可用作此类系统的电极/催化剂。 从中长期能源安全（更不用说气候变化）的角度来看，需要更好地研究、改进和实施本提案中所述的燃料发电技术。 PI在基础地球化学研究以及与太阳能科学家合作方面都有经验，本提案中对串联电池矿物系统的更好理解同样适用于地球化学和太阳能技术。