NSF-DFG Chem: Photocatalytic Organic Synthesis By High-Efficiency Planar Semiconductors

Yale University, New Haven CT

Investigators

Abstract

This project was awarded through the “NSF-DFG Lead Agency Activity in Electrosynthesis and Electrocatalysis (NSF-DFG EChem)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG). This is a collaborative project between researchers at Yale University and Ilmenau University of Technology in Germany. Harnessing solar energy for chemical reactions offers an attractive, low-carbon alternative to traditional thermal chemical manufacturing processes that rely on energy from the combustion of fossil fuels. Adoption of photochemical processes has been slow, however, due to fundamental challenges in the efficient conversion of light into electrochemical energy and directing that energy toward desired chemical reactions. The project addresses both limitations by employing efficient semiconductive photoabsorbers combined with photocatalytic coatings to facilitate the manufacture of organic chemicals. The research effort brings together leading researchers to apply a unique blend of experimental and theoretical methods to the study of photocatalytic chemical manufacturing. Through an international outreach effort, the project will include workforce development and educational outreach, including mentoring science club activities, developing courses in sustainable technologies, and raising public awareness of sustainable chemical production. The joint team will explore the use of efficient semiconductive photoabsorbers to achieve organic synthesis. Presently, the relationship of the charge-transfer energetics and kinetics with surface reactivity is not well understood, which limits the design of synthesis pathways based on photocatalysis. To address this gap, the team investigates a model reaction of photocatalytic para-xylene oxidation to produce terephthalic acid, driven by titanium oxide-coated planar aluminum gallium indium phosphide semiconductors. This model reaction will explore the ability to manipulate the location, free energy, and charge-transfer potentials, as well as the design principles for controlling product distribution. In operando, attenuated total reflection Fourier Transform Infrared Spectroscopy will be used to identify key surface species, which in combination with theory and computational modeling will investigate the measured energetics and product selectivity, while providing insight regarding the surface reaction pathways. The collaborative research thrusts include 1) correlation between the surface chemistry and the hole-transfer energetics, 2) coevolution to achieve product selectivity control, and 3) vapor-phase reactor implementation. Insights from the para-xylene model reaction should extend to technologically important organic synthesis, such as oxidative dehydrogenation, enantioselective cross-coupling, and carbonylation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.