DMREF: Collaborative Research: A Blueprint for Photocatalytic Water Splitting: Mapping Multidimensional Compositional Space to Simultaneously Optimize Thermodynamics and Kinetics

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NON-TECHNICAL DESCRIPTION: Sunlight is a vast source of renewable energy but its intermittent nature means that its utilization requires a means of storing this energy. One attractive approach for solar energy storage is to harness the energy of sunlight to split water into hydrogen and oxygen i.e. solar generated fuels. The solar generated fuels can be combusted to release energy efficiently with water as the only by-product. As a result, this approach avoids the deleterious consequences of greenhouse emissions that accompany the combustion of conventional fossil fuels. The complex cascade of reactions required to harvest sunlight and split water into hydrogen and oxygen present a formidable scientific challenge. The project seeks to develop hybrid materials as the catalyst for water splitting, such that individual components are assembled and function synergistically. The project further works towards employing components that are highly tunable in terms of their energy levels, thereby providing a versatile platform that can be optimized for converting sunlight and water into fuel. Employing a judicious mix of calculations from supercomputers and selective experiments accelerates the rationally design of materials for efficient solar energy storage within chemical bonds. The project team mentors young scientists from underrepresented groups and engages K-12 students and teachers in activities that emphasize the opportunities made available by big data and solar energy.TECHNICAL DESCRIPTION: The project explores the design of programmable heterostructured platforms for photocatalytic water splitting based on interfacing ternary vanadium oxide bronzes with semiconductor quantum dots. In the former compounds, metal cations are intercalated within a variety of open vanadium oxide frameworks, enabling a multitude of compositional possibilities and considerable energy level tuning. Moreover, the energy levels of quantum dots can also be tuned as a function of composition as well as size and the presence of cores. Photocatalytic water splitting requires not just the appropriate alignment of energy levels but also precise control of charge transfer dynamics. Interfacing two versatile and tunable components yields a rich multidimensional space for identification of effective photocatalytic architectures for water oxidation that yield holes at potentials only minimally positive to the water oxidation potential, thereby allowing for efficient conversion of sunlight to solar fuels. The multidimensional parameter space is mapped through a closely integrated and iterative combination of first-principles structure prediction, electronic structure calculations, diversified materials synthesis, detailed spectroscopy, high-throughput screening, and big data analytics. The activity involves development of an open-source platform for statistical analysis and mining of spectroscopic data. A summer research activity engages undergraduates from diverse backgrounds.