CAREER: Time-Resolved Studies of Charge Transfer and Chemical Reactivity at Photoelectrode-Electrolyte Interfaces

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In this project supported by the Chemical Structure Dynamics and Mechanisms (CSDM-A) program of the Chemistry Division, Dr. Yi Rao and his students at Utah State University (USU) will develop sophisticated laser techniques to explore conversion of carbon dioxide (CO2) into fuels at photoelectrode-electrolyte interfaces. Interfaces are thin regions-a few molecules wide-where two bulk phases, such as a solid and liquid, meet. In this case, the boundary is between a solid photoelectrode, a surface where a light-activated reaction can occur, and a liquid that can conduct electricity. The research is advancing our knowledge of reactions of CO2 at interfaces, driven by solar energy and electricity. The work will integrate scientific training and discovery, using laser-based spectroscopic tools as its cornerstone to enhance teaching at the undergraduate and graduate levels. Leveraging this research expertise in an educational context, Dr. Rao plans to facilitate PHOTON FUELS workshops for K-12 students and hosts USU Science Unwrapped outreach events in the local community. This project focuses on ultrafast interfacial charge transfer and chemical reactivity at the photoelectrode-electrolyte interfaces using newly developed interface-selective spectroscopic tools, including time-resolved electronic sum frequency generation (TR-ESFG) and time-resolved vibrational sum frequency generation (TR-VSFG). These techniques, recently developed and established in the Rao group, provide a unique opportunity to advance fundamental knowledge of the PEC reduction of CO2 and other related interfacial phenomena. The expected outcomes of photoelectrochemical reactions at the photoelectrode-electrolyte interfaces include (1) identification of interfacial states and the effect of pH, ionic species, ionic strength, and applied potentials, (2) quantification of binding geometry and strengths of reactants and intermediates, and (3) development of a relationship between interfacial states and intermediates. A broader societal impact of this work is increased understanding of interfacial chemical reactivity of solar fuels. The project also will allow students to gain valuable experience in cutting-edge laser technology, electrochemistry, and materials science.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.