Interfacial engineering of semiconductors for highly selective light-driven chemical transformations

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Due to the distinct aspects of interfacial energetics and reactivity of photoexcited charges at illuminated semiconductors, light-driven heterogeneous photo(electro)catalytic reactions hold special promise for the development of highly selective chemical transformations that might not be easily achieved in conventional thermal catalysis or electrocatalysis. However, the overall performance of heterogeneous selective photocatalytic systems developed so far is still rather low, and the factors governing the selectivity in heterogeneous photocatalysis are still poorly understood. Based on our preliminary work on various light-driven selective conversions, the major thrust of this project is to develop novel and more efficient photo(electro)catalytic systems for various highly attractive conversions (i.e., selective oxidations of alcohols and diphenyl sulfides, reduction of oxygen to hydrogen peroxide, reduction of carbon dioxide) and to gain fundamental mechanistic understanding of the factors governing the kinetics of charge separation, charge recombination and catalytic turnover in direct relation to product selectivity. Specifically, the project aims are: i) to investigate composites combining materials with optimum surface catalytic properties with well-passivated low-gap semiconductors as light harvesters, ii) to study the influence of various types of additional metal catalytic sites (single atoms/ions vs. nanoclusters vs. particles), iii) to develop tandem catalytic configurations of particulate photocatalysts in which the products formed selectively at one component are utilized in-situ by another component for further light-driven selective transformation. These objectives will be addressed by a combination of synthetic (e.g., ALD), photoelectrochemical, spectroscopic (e.g., transient absorption/fluorescence spectroscopy, spectroelectrochemistry, intensity-modulated photocurrent/photovoltage spectroscopy), and theoretical (in particular density functional theory (DFT) and reactive forcefields) studies. The project results are expected to provide unique design rules for the development of highly active and selective photo(electro)catalytic architectures, and to advance our understanding of the fundamental advantages and bottlenecks of such systems for selective catalytic transformations.