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Shoji Hall - Johns Hopkins University

Abstract:

The development of efficient renewable energy conversion and storage devices to curb climate change is one of the most important challenges of the 21^st century. This can be addressed by using renewable electricity to manufacture chemical fuels and synthetic precursors, or by generating electricity with carbon-neutral fuel cell devices. However, electrocatalytic processes are hampered by low efficiencies and poor reaction selectivity because of a lack of rational methods available to create controllable catalyst materials with the preferred electrochemical activities. In this seminar Prof. Hall will discuss the use of ordered intermetallic compounds (OICs), which are alloys that display high electrocatalytic activities because their well-defined compositions and long-range atomic scale ordering enable predictable geometric and electronic interactions, in contrast to the more widely studied solid-solution type alloys. However, OIC materials are difficult to synthesize in nanomaterial form because conventional synthesis methods offer poor control over the composition, phase, and morphology. I will discuss our efforts on the synthesis, stability, and catalytic activity of OICs prepared by electrochemical methods at room temperature and atmospheric pressure. Our strategies include the use of electrochemically induced phase transformations which enables us to convert a base metal rich alloy to an OIC richer in nobler metal by removal of the base metal, and the direct production of OIC materials by electrochemical deposition. We will discuss how we leverage the atomically precise configuration of atoms within OICs to reveal detailed insights into the how a material’s structure dictates its electrochemical properties. Developing new methods for preparing OIC compounds under ambient conditions is essential for designing catalysts for the next generation of renewable energy conversion devices.