Continuous Manufacturing of Anhydrous Metal Sulfide Nanocrystals

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Metal sulfide nanocrystals have attracted great attention because of their excellent properties and widespread applications in diverse fields including lubrication, optoelectronics, catalysis, biotechnology, and energy storage. Reactive precipitation of nanocrystals is typically accomplished by combining aqueous solutions to create supersaturated mixtures. Such processes are sensitive to processing conditions making the synthesis of anhydrous phase pure materials challenging, in general, and impossible for moisture sensitive alloys. This award supports the study of the manufacture of anhydrous metal sulfide nanoparticles through the reaction of hydrogen sulfide gas with metal-organic precursors in an organic solution. The project addresses the engineering challenges involved in translating this solution-based approach into a scalable nanomanufacturing process. It develops a bubble column reactor platform for continuous manufacturing of the nanocrystals via reactive precipitation. The project targets important materials challenges facing next generation battery technologies. Such a manufacturing capability is critical for enabling widespread deployment of renewable wind- and solar-generated electricity, which greatly impacts the nation's prosperity and infrastructure. This project provides interdisciplinary training for undergraduate and graduate engineers and scientists in energy technology areas. Project results are integrated into the undergraduate curriculum. The building and implementation of the bubble-column platform serves as a module in a unit operations laboratory course.This project advances a green chemistry approach that results in complete reduction of the hazardous industrial waste gas hydrogen sulfide while generating metal sulfide nanocrystals and recovering valuable hydrogen. The project aims to extract general principles for the design and operation of reactive precipitation processes in bubble columns, including a four-phase design. The research involves demonstrating the ability to control the size and morphology of metal sulfide nanoparticles through rational selection of chemistry (solvent, auxiliary reagent) and systematic manipulation of mass transport parameters. Studies of nanoparticle synthesis under semi-batch operation are used to guide the design and implementation of a continuous manufacturing platform. The structure, properties and performance of the nanoparticles are characterized through the fabrication and evaluation of prototype cathodes and solid-state electrolytes. Continuous production is expected to improve control over nanocrystal shape and size distribution that is critical in the applications of these materials. The combination of gas-phase reactants with organic solutions offers a new paradigm for the reactive precipitation of moisture sensitive nanoparticles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.