469119 Hierarchical Nickel Carbide “Dandelion” Nanostructure: Controlled Synthesis and Potential Applications

Wednesday, November 16, 2016: 10:30 AM
Golden Gate (Hotel Nikko San Francisco)
Mark T. Swihart, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY and Liang Qiao, Chemical and Biological Engineering, University at Buffalo (SUNY), Buffalo, NY

Transition metal carbides (TMCs), e.g., Ni3C, Mo2C, and WC, can exhibit high electrical and thermal conductivity combined with excellent thermal and mechanical stability due to their mixed covalent-ionic bonding. TMCs can be excellent catalysts with performance comparable to noble metals for some reactions, and can also serve as supports for noble metal catalysts. Rhombohedral nickel carbide, Ni3C, is a common product of nickel carburization during catalysis using Ni. Research on the transformation of Ni to Ni3C helps elucidate its formation mechanism. Recently we reported a hierarchical nickel carbide (Ni3C) nanostructure that resembles a dandelion flower (Qiao et al. Angew. Chemie, 2016). A typical hierarchical nanocrystal (HNC) consists of one core and many radially-arranged branches, most of which are topped by a hexagonal cap. To understand the formation of the Ni3C HNCs, we conducted time-resolved experiments. Quasi-spherical aggregates of primary particles, referred to as “cores”, were observed after 75 min. The Ni content at this point exceeds that of stoichiometric Ni3C. After 80 min, the radial arms have grown in one dimension, and the platelets have begun to grow in the perpendicular direction. From the 75th min to the 80th min, the cores blossomed into midsize HNCs, while also densifying to become non-porous. Further growth of both the arms and the platelets proceeds through the 90th min. The atomic composition of the HNCs matched the stoichiometry of Ni3C, i.e., 75% Ni and 25% C. During evolution from cores to dandelions, the specific surface area (SSA) increased from about 3 m2 g-1 to over 60 m2 g-1. We are presently testing this novel nanomaterial in electrocatalytic applications and will report these results along with the synthesis in this talk. In short, we developed a hierarchical Ni3C “dandelion” nanostructures with specific surface area much larger than that of dense particles of comparable size. Insights into their growth mechanism can enlighten further research on the controlled synthesis of hierarchical nanostructures in solution. In addition, we believe that our current efforts will demonstrate promising applications of this material.

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See more of this Session: Functional Nanoparticles
See more of this Group/Topical: Particle Technology Forum