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

需要为生产氢气(H2)等清洁燃料开发具有成本效益的可再生能源工艺。如果可以通过使用集中太阳光分解水来经济高效地获得H2，那么使用可再生H2发电或基于可再生H2合成其他燃料就有可能运行燃料电池。智力价值拟议研究的总体目标是对金属铁氧体尖晶石通过太阳-热还原/氧化(氧化)循环将水分解为氢气的能力有一个基本的了解。研究的重点是在氧化锆和氧化铝衬底上通过原子层沉积(ALD)法制备镍铁氧体(NixFe3-xO4)。ALD工艺允许精确控制这种材料中的Ni/Fe原子比，并有可能严格控制高比表面积衬底上活性铁氧体的质量负载。将评估各种铁氧体材料和替代水分离循环的性能，以了解它们生产氢气的潜力。要研究的变量包括铁氧体化学计量比、衬底成分、衬底表面积、氧化还原温度、还原升温速率和氧化水浓度。具体测量包括使用热重分析(TGA)对高达1500℃的热还原和高达1200℃的水蒸气氧化进行氧化还原反应速率和热化学循环；通过X射线光电子能谱(XPS)和X射线衍射仪(X射线衍射仪)进行深度剖析，以评估氧化还原循环过程中的化学和结构变化；最后，原子力显微镜(AFM)用于评估铁氧体材料的稳定性，并评估因烧结而导致“孤岛”的可能性。计划在模拟太阳热条件下进行实验，使用配备TGA的高通量太阳炉实时测量加热和冷却速度。通过所有这些方法，可以评估扩散和动力学速率限制对金属铁氧体尖晶石将水分解为氢气的重要性。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，可以以使太阳能热制氢技术可行所需的效率提供高氢气产率。更广泛的影响教育活动将利用现有的国家科学基金会(REU)和教育部(GAANN)计划，在拟议的研究中招收和培训本科生和研究生，包括来自代表性不足群体的学生。还将通过这些项目组织对K12的推广，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.