Controlling functionality and making structure-property correlation in nanostructured metal nitride materials

Abstract

This thesis is focused on exploring the fundamental material properties of nickel-based metal nitride nanocomposites. A thorough review of synthetic pathways and catalytic applications for nickel/nickel nitride materials was conducted. With this information, methods to synthesize and characterize nickel-based metal nitride systems were devised. First, nitrogen-rich deep eutectic solvents were used as templating agents to direct the synthesis of facetted, carbon-encapsulated nickel/nickel nitride nanocomposites. A variety of nitrogen functionalities were identified in these materials, some of which are associated with the nickel metal and others with the carbon support. By adjusting synthesis parameters, control over the surface chemistry can be realized, which provides an opportunity to tune properties. Second, composites of nickel with transition metal nitride supports were investigated, demonstrating that i) nitrogen sites on the support surface act as nucleation sites for nickel particles, which greatly increases nickel dispersion; and ii) metal nitrides affect the electronic structure of supported nickel particles. The close interaction between particles and the nitride support creates a polarization in surface charge, which is hypothesized to be the cause of improved catalytic activity of these composites as compared to a reference composite (nickel on an oxide support). Measures to gain further understanding of metal carbide/nitride formation and their structural stabilization using synthetic techniques and advanced characterization will also be discussed.