Thermochemical production of fuels: Solar energy after dark

太阳在一小时内照射到地球上的能量比地球一年所消耗的能量还要多。因此，现代社会面临的挑战不是确定一种可持续能源，而是如何利用巨大的太阳能资源基础。为了真正改变我们的能源生产技术，我们需要超越有效地捕获太阳能以立即发电，而转向方便地储存这种间歇性能源以供按需利用的问题。为了解决夜间太阳能的这一挑战，我们提出了一种优雅的策略，该策略依赖于选定的金属氧化物的吸氧和释放能力。具体来说，金属氧化物在MO2和MO2-之间循环，使用热能作为输入，氧化态的变化用于生产化学燃料，如面板中氢气生产的示意图所示。理想的热能来自太阳能热集中，但也可以来自核电站。在这项工作中，我们特别关注基于二氧化铈的氧化物，它已经证明了这种应用的前景，同时使用具有广泛的非化学计量范围和快速氧运输动力学的氧化物进行探索性研究。通过仔细选择反应底物和/或明智地使用催化剂，我们不仅可以生产出如图所示的氢燃料，还可以在使用二氧化碳作为额外输入反应物时生产出含碳燃料（合成气、甲烷、甲醇）。除了材料的体积特性之外，我们将探索建筑在优化燃料生产率方面的作用。我们将制造基于反蛋白石结构的整体反应基板，它结合了低扭曲度（对气相质量传输的低阻力），短的固态扩散路径和足够高的表面的特点，并且比颗粒基反应基板更坚固，抗粗化和性能退化。因此，实验计划包含了广泛的热力学和动力学研究，以阐明反应途径，这反过来又对系统优化至关重要。除了这些研究将回答的关于燃料热化学生产的基本科学问题之外，拟议的工作还解决了太阳能储存的关键技术挑战。正如设想的那样，燃料生产过程简单，利用地球上丰富的元素，并允许生产各种还原性化学燃料（H2, CH4， CH3OH等）。广泛的工具与公众对能源技术的高度兴趣相结合，使这成为培训未来材料科学家的理想方案。此外，PI继续致力于公众宣传（例如，通过PI参加加州科学中心关于运输和可持续能源燃料电池的展览），将确保这些成果传播到整个社会。特别是在这个项目中，PI承诺将通过教育进步研究所招收两名暑期高中生来加州理工学院。

CBET-0829114HaileMore energy from sunlight strikes the earth in one hour than all of the energy consumed on the planet in one year. Thus, the challenge modern society faces is not one of identifying a sustainable energy source, but rather one of capitalizing on the vast solar resource base. To truly transform our energy production technologies, we need to go beyond efficient capture of solar energy for immediate electricity generation and turn to the problem of convenient storage of the energy from this intermittent source for on-demand utilization. To address this challenge of solar energy at night, we propose an elegant strategy that relies on the oxygen uptake and release capacity of selected metal oxides. Specifically, a metal oxide is cycled between, for example, MO2 and MO2-, using thermal energy as the input and the changes in oxidation state utilized to produce a chemical fuel, as shown schematically for hydrogen production in the panel. The thermal energy ideally derives from solar-thermal concentration, but may also be derived from nuclear power plants. In this work, we specifically focus on ceria-based oxides, which have already demonstrated promise for this application, while pursuing exploratory studies using oxides with wide non-stoichiometry ranges and rapid oxygen transport kinetics. By careful selection of the reaction substrate and/or judicious use of catalysts, we anticipate production not only of hydrogen fuel, as shown in the panel, but also carbon containing fuels (syngas, methane, methanol) when carbon dioxide is used as an additional input reactant. Beyond the bulk nature of the material, we will explore the role of architecture in optimizing fuel productivity. We will fabricate monolithic reaction substrates based on inverse opal structures, which combine the features of low tortuosity (low resistance to gas phase mass transport), short solid state diffusion paths and sufficiently high surface and are more robust against coarsening and performance degradation than particle based reaction substrates. The experimental plan thus encompasses a broad range of thermodynamic and kinetic studies to elucidate reaction pathways, which, in turn, are essential for system optimization.Beyond the fundamental scientific questions concerning the thermochemical production of fuels that these studies will answer, the proposed work addresses the key technological challenge of solar energy storage. As envisioned, the fuel production process is simple, utilizes earth-abundant elements, and permits production of a variety of reduced chemical fuels (H2, CH4, CH3OH, etc.). The breadth of tools to be utilized combined with the high level of public interest in energy technologies renders this an ideal program for training future materials scientists. Furthermore, the continued commitment of the PI to public outreach (through, for example, the PI's participation in the California Science Center exhibits on fuel cells for transportation and for sustainable energy) will ensure that these results are disseminated to society as a whole. For this program in particular, the PI is committed to hosting two summer high school students who will come to Caltech via the Institute for Educational Advancement.