Tabletop Solution-Phase Femtosecond XUV Transient Absorption Spectroscopy of Transition Metal Photocatalysts
Abstract
In this work, we will use solution-phase extreme ultraviolet transient absorption spectroscopy to measure the electronic structure of key intermediates in H2 reduction catalysts. Transition states and many reactive intermediates in catalytic reactions are too short-lived to characterize with standard tools such as EPR and steady-state X-ray spectroscopy, while fast techniques such as transient UV/Vis and infrared spectroscopy lack chemical specificity or require the presence of vibrational tags. Spectra in the extreme ultraviolet (XUV) spectral region are element-, oxidation state-, spin state-, and ligand field specific, and the laser-based source allows us to probe dynamics on femtosecond to nanosecond timescales.We will append electron donor/acceptor chromophores to functional NiFe hydrogen reduction catalysts, then photoexcite the chromophore to induce charge transfer onto the catalyst. The XUV probe will measure the electronic structure of each metal center as the catalyst passes through transition states and reactive intermediates on the way to its next stable state.The experimental dynamics will be combined with ab initio molecular dynamics calculations to predict how synthetic modifications will affect the rate and detailed mechanism of each catalytic step. Our overall goal is complete characterization and control over the electronic structure of the catalyst at each hidden point of the catalytic cycle. This will improve the design of catalysts for producing fuel for Air Force units in the field. Finally, we will significantly expand U.S. research capabilities by developing the technique of solution-phase XUV transient absorption spectroscopy, transforming an instrument currently used for materials science and gas-phase chemical physics into one that will be widely used to solve problems of general interest in physical, inorganic, and organometallic chemistry.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 11, 2018
- Source ID
- FA95501810293
Entities
People
- Joshua Vura-weis
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Illinois Urbana–Champaign