Layered Inorganic Solids as Building Blocks for Functional Materials

该项目探索层状过渡金属氧化物的化学性质，以便更好地理解催化剂-载体的相互作用，并开发改进的电化学储能材料。研究的两个方面都利用了这样一个事实，即纳米片作为二维晶体，是具有设计结构和涌现特性的材料的良好基石。该项目的一部分建立在发现某些金属和金属氧化物的纳米颗粒在金属氧化物纳米片上支撑时具有异常高的稳定性。量热法、电子显微镜、x射线散射和吸收被用来表征界面键合。这部分项目的主要目标是绘制晚期过渡金属/金属氧化物纳米颗粒与早期过渡金属纳米片之间键合的周期性趋势。该项目的第二部分探索电活性过渡金属氧化物的新合成路线。拓扑化学反应产生无水的、以纳米板形式结合的三维氧化物，这种氧化物可以在石墨烯片的存在下合成，从而制成导电和电活性“卡片”的洗牌。复合材料中的金属离子与导电石墨烯层和渗透其中的电解质密切接触，因此该材料作为超级电容器和电池电极具有非常好的可循环性。这些材料正在通过x射线散射和吸收、电子显微镜和电化学技术的结合来研究。该项目侧重于利用纳米颗粒的协同特性合成新材料。了解和控制金属纳米颗粒的稳定性对多相催化具有重要意义。氧化纳米片和导电石墨烯复合材料的新合成路线也可以为二次电池的发展提供信息，这种电池使用更丰富、更便宜的材料，并且具有更长的循环寿命。这些研究项目与研究生和本科生的培训以及为高中教师和来自弱势学区的K-12学生提供实践研究经验的外展项目相结合。

This project explores the chemistry of layered transition metal oxides in order to better understand catalyst-support interactions and to develop improved materials for electrochemical energy storage. Both aspects of the research exploit the fact that nanosheets, as two dimensional crystals, are good building blocks for materials with designed structures and emergent properties. One part of the project builds on the discovery that nanoparticles of certain metals and metal oxides have anomalously high stability when supported on metal oxide nanosheets. Calorimetry, electron microscopy, and X-ray scattering and absorption are being used to characterize the interfacial bonding. The primary goal of this part of the project is to map the periodic trends in bonding between late transition metal/metal oxide nanoparticles and early transition metal nanosheets. A second part of the project explores new synthetic routes to electroactive transition metal oxides. Topochemical reactions produce anhydrous, three-dimensionally bonded oxides in the form of nanoplates, which can be synthesized in the presence of graphene sheets to make a shuffled deck of conducting and electroactive "cards." Metal ions in the composites are in close contact with both the conducting graphene layers and the electrolyte that permeates them, and thus the materials have very good cyclability as supercapacitor and battery electrodes. These materials are being studied by a combination of X-ray scattering and absorption, electron microscopy, and electrochemical techniques.This project focuses on the synthesis of new materials that exploit the synergistic properties of nanoparticles. Understanding and controlling the stabilization of metal nanoparticles can have an important impact in heterogeneous catalysis. New synthetic routes to composites of oxide nanosheets and conducting graphene can also inform the development of secondary batteries that use more abundant, less expensive materials and have much longer cycling life. These research projects are integrated with the training of graduate and undergraduate students, as well as with outreach programs that provide hands-on research experiences for high school teachers and for K-12 students from disadvantaged school districts.