Professor Royce W. Murray of the University of North Carolina at Chapel Hill is supported by the Chemical Catalysis Program in the Division of Chemistry to study the electrocatalytic oxidation of water by solution-dispersed iridium oxide nanoparticles, and to enhance the analytical capabilities for determining the composition and properties of very small nanoparticles. Specifically, the research plan seeks a better understanding of the mechanisms by which un-supported and supported iridium oxide nanoparticles are effective as water oxidation catalysts, and seeks the development of new measurement techniques to determine the detailed composition and surface chemistry of nanoparticles. The central aims of this project are to develop techniques to enable the control of the size and determine the composition of nanoparticles and to advance our understanding of the mechanisms in electrocatalytic water splitting. This should ultimately contribute to the design of nanoparticle-based devices such as photochemical energy conversion systems and sensors. Students and postdoctoral researchers will be trained in cutting edge electrochemical techniques with relevance to alternative energy research.
These images illustrate use of nanoparticles, of about 2-3 nanometer diameter, in composiitonal design for study of their electrochemical reactions. Image 1 outlines the different kinds of fundamental chemical questions that can be addressed given an ability to prepare these very small nanoparticles, all of aboiut the same size. Image 2 shows the different steps in the chemical synthesis and image characterization of the nanoparticle, which has a gold core and a variety of attached ligands. Image 3 shows details of the detailed structure of a gold nanoparticle containing 25 gold atoms and 18 thiolate ligands, gained from single crystal X-ray structure determination. Image 4 shows how a large number of electrons can be exchanged between an electrode surface and a nanoparticle bearing about 600 ferrocene substituents. This occurs one-at-a-time, by rapid rotational diffusion of the nanoparticle at the electrode surface. Image 5 shows how the rate of electrons transferring between a small nanoparticle and an electrode can be controlled using a molecular tunneling bridge. These and related images have been part of scientific lectures given at professional meetings and at universities to which I have been invited. A typical lecture would contain between 25 and 35 analogous images to be used in delivering a lecture on the science and electrochemistry of nanoparticles. I give between 15 and 25 such lectures per year, at mainly department of chemistry seminars and colloquia.
