EAGER: COLLABORATIVE RESEARCH: Hybrid Quantum Dot-Metal Nanocrystals for Photoreduction of CO2: Synthesis, Spectroscopy and Catalysis

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Efficient, sustainable, and cost-effective reaction of combustion-generated carbon dioxide to fuels and chemicals remains one of the leading technical challenges of our times. Among sustainable technologies, the direct conversion of solar energy to chemical energy, as accelerated by catalytic materials, is one of the most attractive options, but is limited by the efficiency of the solar-to-chemical energy conversion. The project will investigate a new combination of catalytic materials, and methods for structuring those materials, that has potential to further increase both the rate and efficiency of solar-driven carbon dioxide reactions. The study also utilizes an ultrafast spectroscopic technique that may shed new light on the energy conversion process - knowledge that can be extended to a wide range of applications beyond photocatalysis. The project will generate insight that supports technologies critical to our nation's future energy security while decreasing carbon emissions.Energy sustainability and environmental protection has created an urgent need to develop new methods that efficiently, selectively, and sustainably convert carbon dioxide (CO2) into valuable chemicals and fuels. Among existing technologies, solar-driven photoreduction and transformation of CO2 into carbon-based fuels represents an attractive method due to its sustainability and its minimal environmental impact. High-performance photocatalysts are the key to achieving effective CO2 photoreduction. The collaborative project will perform proof-of-principle studies of novel nanocatalysts for solar-driven CO2 photoreduction based on hybrids of semiconductor core@shell quantum dots (QDs, e.g., CdSe@CdS) and gold (Au) nanoparticles (NPs). CdSe@CdS core-shell QDs can efficiently capture solar energy in the entire ultraviolet and most of the visible spectral range due to their low bandgap of 1.9 eV as well as having a highly reductive conduction band. Meanwhile, Au NPs show high CO2 binding affinity and excellent reaction selectivity (e.g., CO2 to CO). Coupling CdSe@CdS semiconductor QDs with Au NPs through direct epitaxial growth has the potential to greatly improve the overall conversion efficiency of solar energy to chemical fuels. To this end, the project will explore new synthetic methods towards synthesizing QD-metal hybrid nanomaterials with precise control over size, shape, geometry, and lattice strain. The unique HNC structures make it possible to efficiently transfer multiple electrons as quantitatively detected by ultrafast transient absorption spectroscopy, thereby providing fundamental understanding of the relationships between structural parameters and charge separation/transfer processes between the QDs and Au, as well as photocatalytic performance of QD-Au. Beyond the technical aspects of the project, the investigators will collaborate in organizing annual events such as workshops and outreach days featuring nanoscience and clean energy at both universities. The outreach activities will be designed to stimulate the interests of students from high schools in pursing STEM-related higher education. In addition, scientific symposia will be organized with the goal of highlighting research opportunities related to photocatalytic CO2 reduction.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.