SusChEM: Mechanistic Studies of Photocatalytic Water-Splitting and CO2Reduction: The control of surface chemical reactivity and its effect on product distribution

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SusChEM: Mechanistic Studies of Photocatalytic Water-Splitting and CO2 Reduction: The control of surface chemical reactivity and its effect on product distributionDeveloping inexpensive catalytic materials that efficiently use solar energy to transform simple, readily-available substances into sustainably-produced fuels and chemicals is one of the grand challenges of the 21st century. This photocatalytic process is called "Artificial Photosynthesis" and is pursued for its promise of supplying cheap, clean energy and chemicals from carbon dioxide (CO2) and water (H2O). Currently, scientists do not completely understand how photocatalytic reactions can be controlled to produce the most desirable chemicals out of a large number of potential products. In this project, Dr. Laursen is developing an understanding of exactly how to control the surface chemical reactivity of Artificial Photosynthesis. A high level of control is critical if we are to produce the fuel or building-block chemicals selectively in an environmentally responsible fashion, as needed by our society. Dr. Laursen is actively engaged in outreach activities that build upon his research to promote engagement of students in science, technology, engineering and mathematics (STEM) disciplines. These activities, which include summer research internships in Dr. Laursen's laboratory, are directed at improving the education of promising high school seniors and women students and encouraging their interest in STEM careers. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Siris Laursen of the University of Tennessee - Knoxville is developing a fundamental understanding of how the surface properties of Bi2S3, GaP, and CdS semiconductor photocatalysts dictate their catalytic activity and product selectivity in the reduction of CO2 and H2O to hydrogen, methane and simple oxygenated hydrocarbons. The surface-bound intermediates important in the mechanisms that determine catalyst efficacy are followed with in situ Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTS) to correlate the thermochemical stability of the various intermediate species with reaction rate and product selectivity. Also under investigation is how the chemical nature of surface bound hydrogen can be controlled to produce reduced organic molecules preferentially over molecular hydrogen or carbon monoxide. Density functional theory (DFT) calculations are carried out in parallel to the experimental work, and are used in support of structure-activity and composition-activity property determination. Dr. Laursen is actively engaged in STEM outreach programs focused on female student recruitment into the STEM fields and in high school student research internships, in support of the broader impacts of the project.