Solar-powered production of fuels such as methanol from carbon dioxide (CO2) offers the potential to enable solar power, which is available on a transient basis, to be stored in the form of a chemical fuel for transport and other applications. Efficient and cost-effective production of solar fuels remains a scientific and technological challenge with issues of efficiency, cost, and materials durability. This collaborative project aims to design innovative materials that are capable of converting carbon dioxide and hydrogen to methanol using natural sunlight as the only energy input. This class of materials will consist of multiple components, including two types of metal nanoparticle catalysts that are separately placed within porous nanostructures of the catalyst system. By harvesting light, one of the metal nanoparticle catalyst will produce both heat and hot electrons to activate the carbon dioxide molecules. The other metal catalyst will split hydrogen molecules into hydrogen atoms, which are also needed for converting carbon dioxide to methanol. Results obtained through this project will offer fundamental insights and practical guidelines to achieving low-temperature conversion of carbon dioxide to liquid fuels using solar energy. The research will be incorporated into outreach activities for high school teachers and students as well as summer research activities for undergraduate students. Workshops on nanoscience and clean energy will be designed and offered to local high school students and K-12 science teachers in the New England area.
Among the methods for carbon dioxide utilization, hydrogenation which employs dihydrogen as an electron donor and proton source to reduce carbon dioxide to high-value fuels is of particular interest, due to its sustainability and low environmental impact. Hydrogenation of carbon dioxide, however, often requires operation at high temperature because a large energy input is needed to activate carbon dioxide, even in the presence of catalysts. The focus of this collaborative effort is to design a new class of hierarchical hybrid photocatalysts that can harness visible light to mediate hydrogenation of carbon dioxide at room temperature. The first objective of this project is to synthesize hybrid photocatalysts consisting of porous titanium dioxides and spatially isolated nanoparticles of Au and Pt. The plasmonic Au nanoparticles will harvest visible light and subsequently convert photons to thermal energy and generate hot electrons for carbon dioxide activation. The Pt nanoparticles will facilitate hydrogen adsorption and dissociation. The second objective of this project is to investigate the hybrid photocatalysts in cooperatively catalyzing carbon dioxide activation and hydrogen spillover to achieve solar hydrogenation of carbon dioxide. Mechanistic studies using in situ infrared spectroscopic studies will be conducted to establish correlations between nanostructures of the hybrid materials and their catalytic performance. The outcome of solar-driven hydrogenation using these hybrid photocatalysts will illustrate a new pathway to convert carbon dioxide to liquid fuels by utilizing renewable energy sources.
