Early Career Lecture Series: Dr. Jill Wenderott, Northwestern

Spring 2021 Early Career Lecture Series in Materials Science & Engineering

Speaker:  Dr. Jill Wenderott

Department of Materials Science & Engineering, Northwestern University

Subject:  Elucidating Synthesis Pathways to Molybdenum Oxynitrides for
Use in Catalysis Applications

Abstract:

Molybdenum nitrides, typically the cubic γ-Mo2N and hexagonal MoN phases, have been investigated for their utilization in a variety of electronic and catalysis applications. These molybdenum nitrides are often synthesized via ammonolysis of molybdenum oxide powders at elevated temperatures. Commonly, ammonolysis of molybdenum trioxide (MoO3
) to form phase pure cubic γ-Mo2N is reported, and multiple reaction pathways have been proposed which
generally include the formation of intermediates molybdenum dioxide (MoO2) and molybdenum bronze (HxMoO3
). Our ammonolysis studies indicate numerous factors including precursor, heating rate, maximum reaction temperature, and gas composition influence the phase fraction, chemical composition, and surface area of the final nitride product(s). Thus, insights gleaned from probing reaction pathways to these molybdenum nitrides can promote both chemical and
physical tunability of the final product. In this talk, first, the structure and composition of the so-called molybdenum “nitride” γ-Mo2N that forms phase pure from MoO3 will be discussed to reveal its identity as a hydrogen-incorporated molybdenum oxynitride. Next, the reaction pathway to this molybdenum oxynitride illuminated via in situ powder X-ray diffraction will be presented. We find that the reaction from MoO3 does proceed through MoO2 and HxMoO3 as
often described in literature, but the unique nature of the intermediates enables phase pure formation of the nitride product. Leveraging these in situ findings, exotic molybdenum bronze precursors that circumvent the intermediate formation of MoO2 altogether were utilized to produce phase pure molybdenum oxynitrides at the lowest reaction temperatures and highest surface areas reported in literature to date.  The reaction pathways from bronze precursors to high surface area molybdenum oxynitrides will be discussed, as well as the potential of the high surface area products for application in catalysis.

Biography:

Jill K. Wenderott is currently a postdoctoral scholar in the Department of Materials Science and Engineering at Northwestern University investigating heteroanionic oxynitride materials for catalysis applications under the supervision of Prof. Sossina Haile. Jill completed her B.S. in Physics at the University of Kansas (2014) before receiving her Ph.D. in Materials Science and Engineering from the University of Michigan (2018) in Prof. Peter Green’s group. Her Ph.D.
focused on understanding the connection between conjugated polymer thin film morphology and electronic properties using advanced atomic force microscopy techniques. Jill was a Rackham Merit Fellow at the University of Michigan, and recently as a postdoc, her team was awarded the 2020 American Physical Society Innovation Fund to support their program, Women Supporting Women in the Sciences.