Optimization of the Electrical and Dielectric Properties of Hydrogen Bonded Solids for Fuel Cell and Other Applications

本研究的目的是阐明固体酸性硫酸盐、硒酸盐和磷酸盐中氢键、相变和电学性质之间的关系。这些化合物表现出多种结构类型，其中氢键的程度和类型变化很大。此外，剧烈的性质变化伴随着结构相变。广泛的实验技术将被用于表征材料（x射线和中子衍射，红外，拉曼，核磁共振和阻抗谱，热分析），并将辅以计算模拟来预测先验的相变行为。这些综合研究将指导人们(1)控制转变发生的温度，(2)增加超质子相的电导率和铁电相的自发极化，以及(3)合成具有理想氢键特征的假设结构。最终，室温超质子导体和铁电体可能实现。可以利用的工具的广度，材料的合成相对容易，以及公众对能源技术的高度兴趣，使其成为培训下一代材料化学家的理想系统。这项研究的目标是促进对一类被称为固体酸的材料的基本理解。这种理解将使性能的优化和新的超质子导体和铁电体的发展具有增强的性能。质子导体在湿度和氢传感器、燃料和电解电池、高能量密度电池、作为电容器的铁电体和光电器件中都有应用。燃料电池，因为它们与可持续能源的未来相关，是这项研究的主要推动力。固体酸化合物与传统燃料电池材料截然不同。它们在降低燃料电池系统的复杂性和成本方面提供了潜在的好处。然而，将它们结合到示范燃料电池中还处于起步阶段，因此这种材料对工业实验室来说风险太大。另一方面，固体酸性化合物的合成相对容易，以及在这项工作中使用的广泛的表征工具，使这个项目非常适合培养从高中到博士后学者水平的学生。学生的培养范围从高中生的短期访问，到本科生的毕业论文，再到博士生的深入培养。基础科学、重要的技术成果和强大的教育推广相结合，证明联邦政府支持这项研究是合理的。

The goal of this research is to elucidate the correlation between hydrogen bonding, phase transitions and electrical properties in solid acid sulfates, selenates and phosphates. These compounds exhibit numerous structure types, in which the extent and type of hydrogen bonding vary dramatically. Moreover, dramatic changes in properties accompany structural phase transitions. A broad range of experimental techniques will be employed to characterize the materials (X-ray and neutron diffraction, IR, Raman, NMR and impedance spectroscopy, and thermal analysis) and will be complimented by computational simulations to predict phase transition behavior a priori. These comprehensive studies will guide efforts to (1) control the temperature at which the transitions occur, (2) increase the conductivity in the superprotonic phases and the spontaneous polarization in the ferroelectric phases, and (3) to synthesize hypothesized structures with desirable hydrogen-bonding features. Ultimately, room temperature superprotonic conductors and ferroelectrics may be achieved. The breadth of tools to be utilized, the relative ease with which the materials can be synthesized, and the high level of public interest in energy technologies, renders this an ideal system for training the next generation of materials chemists.%%%The goal of this research is to advance a fundamental understanding of a class of materials known as solid acids. This understanding will enable the optimization of properties and the development of new superprotonic conductors and ferroelectrics with enhanced performance. Proton conductors have applications in humidity and hydrogen sensors, fuel and electrolysis cells, and high energy density batteries, and ferroelectrics as capacitors and in electro-optical devices. Fuel cells, because of their relevance to a sustainable energy future, are the major drivers for this research. Solid acid compounds are a radical departure from traditional fuel cell materials. They offer potential benefits in terms of reduced complexity and cost of the fuel cell system. However, their incorporation into demonstration fuel cells is in its infancy, and consequently the materials are of too great a risk for industrial laboratories. On the other hand, the relative ease with which solid acid compounds can be synthesized as well as the broad range of characterization tools that will be employed in this work, render this project ideal for training students from the high school level through the post-doctoral scholar level. Student training ranging from short visits by high-school students, to senior theses by undergraduates, to in-depth training of doctoral students will be pursued. The combination of fundamental science, important technological consequences, and strong educational outreach justify federal support for this research.