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.
