Sulfide catalysts for biomass valorization and environmental remediation: Interactions of complex organic molecules on well-defined sulfide surfaces

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The study of well-defined sulfide surfaces and how they interact with organic molecules has been lacking. We aim to fill this gap by combining surface science techniques with material/catalysis work and open a new area of investigation in catalysis. The general long-term objective of my research program is to understand, at the molecular level, the properties and chemical transformations of complex, usually defective material surfaces. Surface science revolutionized the use of catalysis in industry with fundamental discoveries using metal single crystals and subsequent work on oxides, films and nanoparticles in ultra high vacuum. Fundamental understanding of molecule-surface interactions on sulfide surfaces can now revolutionize catalyst usage, guiding sulfide catalyst use in industries such as biomass valorization, volatile organic carbon removal from the environment and photocatalysis for energy production. The interplay between surface science and materials proposed here will lead to the preparation and characterization of new sulfide catalysts and their interactions with aromatic and oxygenated organic species. Our unique approach of combining fundamental understanding of the chemical reactions, mechanisms and intermediates with the synthesis and use of nano-structured materials prepared on this basis leads to enhanced catalytic performance and the generalization of common factors (reaction sites, intermediates, molecular geometries, etc) that will guide future catalyst design. Surface properties of the sulfides such as segregation at the interphase, surface termination and sulfur or hydrogen lability in different environments determine the molecule-surface interactions. Overall, we will contribute to an overarching understanding of catalyst reactivity with extensive predictive power as to their properties for both catalytic and photocatalytic reactions. The proposal is designed for 5 HQPs per year to be trained over the course of the 5 year grant. We will initially use CdS and ZnS single crystal surfaces and nanoparticles to: -Prepare and understand well defined sulfide surfaces -Identify and characterize adsorption species of organic molecules on the well defined sulfide surfaces -Identify and characterize co-adsorption behavior for reactants relevant to hydrogenation, oxidation and hydrodeoxygenation reactions -Provide insight regarding reaction intermediates and mechanisms -Synthesize and test controlled nano-catalysts with the desired surfaces The impact of this work is manifold. We hope to develop viable catalysts and identify reaction conditions for catalytic and photocatalytic removal of volatile organic carbons. This is essential for our environment, leading to devices that provide a clean household atmosphere or to the removal of atmospheric pollutants. Similarly, we aim to achieve an active material for the hydrodeoxygenation of biomass derived molecules leading to a high economic impact in the valorization of biomass.