CAREER: Advanced Aerosol Synthesis of Metal Oxides for Photocatalytic Applications

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TECHNICAL SUMMARYOf fundamental importance is the discovery of new synthetic techniques that can be predictably manipulated to yield materials with defined and controllable features. While widely recognized as a powerful route to compositionally-complex inorganic solids, ultrasonic spray pyrolysis (USP), which is an aerosol-based synthetic technique that uses ultrasound for nebulization, has been under-realized as a synthetic route to architecturally-diverse particles. This CAREER project, supported by the Solid State and Materials Chemistry (SSMC) program will emphasize precursor design and decomposition behavior, as well as aerosol droplet phase and surface chemistry, to achieve architecturally-diverse particles with USP for photocatalytic applications including water splitting for solar H2 generation. Synthetic targets include i) highly-tailored titania photocatalysts in which porosity, crystal phase distribution, and surface decoration are controlled and ii) visible light driven O2-evolving photocatalysts with high active site dispersion. The former will be achieved by exploiting a newly discovered salt-assisted route to porous particles in which low-melting salt mixtures serve as a pore template and pre-formed titania colloids serve as the building blocks to the larger porous particles. The latter will be achieved by targeting valence band modified transition metal oxides. In this case, architecturally-diverse particles will be achieved with USP by deviating from convention and selecting precursors that yield templates and/or structure-directing agents via i) reaction (e.g., metathesis approaches) or ii) decomposition from single-source precursors. Given that the proposed research addresses such a timely issue, the development of sustainable energy sources, it is also of utmost importance that considerable effort be spent educating the community about it. To this aim, an Energy Ambassadors' Program is proposed in which undergraduates, with guidance from senior laboratory members, return to their high schools to discuss their research through an engaging demonstration.NON-TECHNICAL SUMMARYSubstantial resources are being directed toward the development of alternative energy platforms in attempts to minimize the potentially catastrophic effects associated with the burning of fossil fuels. Given that the sun provides the Earth with 120,000 trillion watts (TW) of energy, solar energy conversion represents the most viable means of sustainably producing 13 TW, which is consistent with global human demand. The proposed research aims to develop new materials for harnessing the energy of the sun to split water into hydrogen (H2) and oxygen (O2), with H2 representing a clean fuel that does not emit greenhouse gases or other pollutants upon use. The new materials will be prepared by an aerosol-based synthetic approach, with an emphasis on discovering new ways in which the architecture and shape of the resulting particles can be controlled by producing structure-directing agents using chemical methods. Controlling the shape and architecture of the prepared particles potentially provides a way in which the desirable features of a material can be enhanced selectively, thus maximizing their light harvesting properties and surface reactivity. Given that the proposed research addresses such a timely issue, it is also important that effort be spent educating the community about solar energy science. Thus, an Energy Ambassadors' Program is proposed in which undergraduates, with guidance from senior laboratory members, return to their high schools to discuss their research through an engaging demonstration.