Rapid, Flexible Growth of Crystalline Earth-Abundant Metal Borides for Molecule-Surface Investigations Relevant to Electrocatalytic Hydrogen and Nitrogen Reduction Reactions

In this project, Professor Edward Gillan of the Department of Chemistry at the University of Iowa is developing facile and tunable materials growth strategies for the design of earth-abundant metal boride solids that can facilitate desirable chemical transformations. Two of these transformations are the production of high energy hydrogen from water and valuable ammonia from abundant atmospheric nitrogen. Many current and future national needs in energy security and efficiency hinge on our improved fundamental understanding of chemical and materials processes that convert abundant resources into valued-added chemicals. Students from high school to undergraduate and graduate levels will gain materials synthesis and chemical characterization experience and become proficient in synthetic experimental design. They will produce metal boride materials and examine them as electrocatalysts for energy efficient conversions of water into hydrogen and nitrogen into ammonia. The synthetic methods and catalytic investigations developed here may be applicable to other important materials and catalytic systems. Importantly, the students working on this project will receive education and advanced training in materials growth and catalyst design that will benefit their future careers as members of a technologically proficient U.S. scientific workforce leading innovations in advanced manufacturing related to both materials growth and valuable chemical transformations. The goals of this project are to investigate thermochemically driven rapid reactions that form crystalline metal borides, particularly those in the earth abundant 3d and 4d metal families with high boron content, including structures with direct boron-boron bonding. These highly exothermic reactions occur in seconds and can produce crystalline boride materials and intimately mixed composites that grow in a transient molten salt flux. This study will identify key factors that impact metal boride compositional and structural tuning in rapid thermochemical reactions. The metal boride targets are expected to be chemically robust electrical conductors and provide electrocatalytically active surfaces to facilitate the conversion of water to hydrogen, and impact the challenging conversion of nitrogen to ammonia. Students working on this project will spectroscopically investigate molecule-surface reactions on boride catalysts to improve the understanding of metal boride electrocatalyst reactivity. Spectroscopic and microscopic experiments will investigate relevant molecule-surface bonding interactions focusing on the influence of boron-rich and boron-boron bonded surfaces. Experimental catalytic reactions and spectroscopic studies will be coupled with theoretical calculations of surface bonding and energetics to identify reactions and intermediates relevant to water and nitrogen reduction reactions on metal boride surfaces. This work will expand the materials chemistry synthetic toolbox for crystalline metal boride growth and provide spectroscopic results that improve our molecular level understanding of factors that impact metal boride catalytic activity. 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.