Thin Film Metal Ferrite Spinels for Solar-thermochemical Redox Cycles to Split Water

0966201 Weimer需要开发成本效益高的可再生能源工艺，用于生产清洁燃料，如氢气（H2）。 如果H2可以通过使用集中的太阳光分解水来成本有效地获得，则可以使用可再生H2来操作燃料电池以发电或基于可再生H2合成其他燃料。智力优点拟议研究的总体目标是发展的能力的金属铁氧体尖晶石通过太阳能热还原/氧化（REDOX）循环分解成氢气的基本理解。研究的重点是通过原子层沉积（ALD）在氧化锆和氧化铝衬底上制备镍铁氧体（NixFe 3-xO 4）。ALD工艺允许精确控制这种材料中Ni/Fe的原子比，并且还具有对高表面积基底上活性铁氧体的质量负载进行严格控制的潜力。各种铁氧体材料和替代水裂解循环的性能将被评估其产生H2的潜力。 要研究的变量包括铁氧体化学计量，基板组合物，基板表面积，REDOX温度，还原加热速率，和水的氧化浓度。 具体测量包括使用热重分析（TGA）的REDOX反应速率和热化学循环，用于高达1500 ℃的热还原和高达1200 ℃的蒸汽氧化;通过X射线光电子能谱（XPS）和X射线衍射（XRD）的深度分析，以评估REDOX循环期间的化学和结构变化;最后，原子力显微镜（AFM）评估铁氧体材料的坚固性，并评估烧结导致的“孤岛”的可能性。 实验计划进行的REDOX循环模拟太阳能热条件下使用高通量太阳能炉配备了热重实时测量的加热和冷却速率。 通过所有这些方法，可以评估扩散与动力学速率限制对金属铁氧体尖晶石将水分解为H2的重要性。拟议的研究具有潜在的变革性，因为通过ALD工艺生产的金属铁氧体材料具有独特的潜力，可以提供高氢气生产速率，从而使太阳能热制氢技术可行。 更广泛的影响教育活动将利用现有的NSF（REU）和教育部计划（GAANN）招募和培训本科生和研究生，包括来自代表性不足群体的学生。 K12的推广也将通过这些计划组织，使用参与拟议研究的学生。

0966201WeimerThere is a need to develop cost-effective, renewable energy processes for the production of clean fuels such as hydrogen gas (H2). If H2 can be obtained cost effectively by the splitting of water using concentrated sunlight, then it is possible to operate a fuel cell using renewable H2 to generate electricity or to synthesize other fuels based on renewable H2. Intellectual Merit The overall objective of the proposed research is to develop a fundamental understanding of the ability of metal ferrite spinels to split water into hydrogen gas via a solar-thermal reduction/oxidation (REDOX) cycle. The focus of the research is nickel ferrite (NixFe3-xO4) produced through atomic layer deposition (ALD) on zirconia and alumina substrates. The ALD process allows for precise control of the atomic ratio of Ni/Fe in this material, and also has the potential to provide tight control over the mass loadings of the active ferrite on high surface area substrates.The performance of various ferrite materials and alternative water splitting cycles will be evaluated for their potential to produce H2. Variables to be investigated include ferrite stoichiometry, substrate composition, substrate surface area, REDOX temperatures, rate of reduction heating, and water concentration for oxidation. Specific measurements include REDOX reaction rates and thermochemical cycling using thermogravimetric analysis (TGA) for both thermal reduction at up to 1500 C and steam oxidation at up to 1200 C; depth profiling via X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to evaluate chemical and structural changes during REDOX cycling; and finally, atomic force microscopy (AFM) to evaluate the robustness of ferrite materials and to assess the possibility of "islanding" resulting from sintering. Experiments are planned to carry out the REDOX cycles under simulated solar-thermal conditions using a High Flux Solar Furnace equipped with a TGA for real-time measurement of heating and cooling rates. By all of these approaches, the importance of diffusion vs. kinetic rate limitations on the splitting of water to H2 by metal ferrite spinels can be assessed.The proposed research is potentially transformative because metal ferrite materials produced through the ALD process have unique a potential to provide high hydrogen gas production rates at the efficiencies needed to make solar-thermal hydrogen production technology viable. Broader ImpactThe education activities will make use of existing NSF (REU) and Department of Education programs (GAANN) to recruit and train undergraduate and graduate students in the proposed research, including students from under-represented groups. Outreach to K12 will also be organized through these programs using students involved in the proposed research.