Overview
The Weber group will investigate the electronic and geometric structures of selected ruthenium- and copper-based catalysts for water oxidation, as well as of reaction intermediates in the catalytic cycle. Ions of catalysts and reaction intermediates are transferred into the gas phase by electrospray ionization. The ions are cooled in an ion trap, mass selected and irradiated by pulsed light, which is tunable throughout the mid-infrared, visible and near-ultraviolet spectrum. Photon absorption is monitored by photofragmentation of the target ions, allowing the measurement of their vibrational and electronic spectra. Cooling the ions to low temperatures is crucial to obtain the necessary spectroscopic detail. Vibrational spectra will result in structural information on the ions under study, which is particularly important for reaction intermediates. Measuring the electronic spectra of catalysts and reaction intermediates will aid clarification of speciation in reactive solutions. In addition, the excited state vibrational structure will help modeling excited state dynamics and reactivity.
Intellectual Merit
The generation of a sustainable energy economy is one of the most important technological advances to be attained in the next decades. One of the most promising avenues towards this goal is the electrochemical or photoelectrochemical conversion of carbon dioxide and water into chemically useable fuels. For this process to be economically viable, catalysts for the multielectron/multiproton redox chemistry need to be developed. In many approaches to this problem, catalytic water oxidation is used to supply the electrons and protons needed for solar fuel generation. However, the molecular-level mechanisms involving the different steps in the catalytic cycle are often poorly understood, hindering the rational design of such catalysts.
One of the main problems on the road to understanding the mechanisms underlying these catalytic processes is that many different species are present in reactive solutions, making condensed phase identification and study of key molecules and reaction intermediates very difficult. Since homogeneous catalysts and reaction intermediates in water oxidation catalysis are often ions, an elegant way to circumvent this issue is to selectively prepare and study the species of interest in the gas phase. Mass spectrometric preparation of ions from solutions in concert with laser spectroscopy is a powerful approach to do this.
Broader Impacts
The chemistry explored in the proposed work will be of considerable benefit to many areas of science, particularly to chemical energy science and chemical engineering. Under the assumption that many areas of technology will continue to depend on the use of carbon based chemical fuels for the foreseeable future, environmental as well as economic and geopolitical pressures call for the development of fuel sources independent from fossil fuels. The understanding of the reactions at play in solar fuels catalysis will aid in the development of new catalysts for the generation of chemical fuels from sustainable sources.
Additionally, the proposed work has important educational aspects. In addition to the laboratory research, an educational JAVA applet will be developed to enhance student understanding of the quantum mechanical treatment of angular momentum. The experiments, computational research and the JAVA applet development will be carried out by graduate student researchers. This will contribute to the education of the next generation of scientists who will be trained in a broad range of laboratory techniques as well as interactive teaching technology.
The PI will be involved in the enormously successful CU Wizards outreach program. This is a continuing Saturday morning lecture series that treats topics in astronomy, chemistry, engineering, and physics, and is intended primarily for students in grades five through nine. The PI contributes an interactive lecture to this series with many experimental demonstrations, introducing the audience to the world of buoyancy and water displacement.