(3ae) Reshaping the Carbon Cycle with Catalysis: Selective Activation of Chemical Bonds for Producing Carbon Neutral Fuel and Chemicals

Research Interests:

A grand challenge for catalysis this century is to accelerate the carbon cycle–wherein fossil fuels derived from biomass formed over 300 million years ago are extracted from the ground and then used to produce energy, fine chemicals, and environmentally damaging greenhouse gases–to the speed of catalytic chemistry. While renewable energy sources like solar or wind power are promising, they do not meet the energy density requirements for, specifically, automobile propulsion. Additionally, many chemicals crucial to the production of pharmaceuticals, plastics, and adhesives also use fossil fuel sources. In order to sustainably address these energy and chemical needs, new fundamental chemistries and technologies are required that will enable creation of new “oil” and chemical feedstocks from carbon neutral sources like biomass.

There is a critical need for fundamental insights into the chemical identity of catalytic active sites and the interplay between such sites and the reaction environment. By integrating quantum mechanical simulations and state-of-the-art microscopic, spectroscopic, and kinetic experiments, I will interrogate reaction events at the molecular level and establish the catalytic rules that lead to selective activation of chemical bonds on materials ranging from extended surfaces to nanoparticle-support interfaces under realistic reaction environments (e.g. high pressures and solvents). This research program contrasts with the data science approach. As purely computational methods often fail to replicate experimental data in even the simplest systems, there is no reason to believe scaling up of computational data via data science techniques (where errors can potentially be magnified) will provide any further fundamental insights into catalysis. My specific approach will be to use kinetic and spectroscopic experiments to reduce the parameter space of highly complex catalytic systems of promise wherein congruence to experimental data provides the means to navigate any computed data that are within the known errors and limitations of computational methods. This methodology will allow me to probe the nature of catalytic active sites, transitions states, and reaction steps in a truly atom resolved manner without relying solely on often error prone or ambiguous computational data. Furthermore, my background in merging computational chemistry and experimental spectroscopic and kinetic techniques prepares me to tackle highly challenging catalytic systems covering homogeneous and heterogeneous catalysis in both vapor and condensed phases. Overall, my goal is to identify molecular level properties at chemically active interfaces which can then be leveraged to enhance catalytic performance of reactions used for the sustainable production of carbon neutral fuels and fine chemicals.

Successful Proposals:

Environmental Molecular Sciences Laboratory General Cycle Proposal, 2019

Proposal Title: Uncovering the Atomistic-Scale Catalytic Roles of Hydrogen Transfer at Liquid-Solid Interfaces for the Targeted Removal of Oxygen from Bio-Oil Compounds

U.S. Department of Energy Office of Science Graduate Student Research Award, 2015

Proposal Title: Efficient Development of Earth Abundant Catalysts: Elucidating the Aqueous Phase Deoxygenation Mechanism of Phenolics for Upgrading Bio-oils to Usable Biofuels

Center for Nanoscale Materials at Argonne National Lab High-Impact Nanoscience and Nanotechnology User Proposals, 2013-2016

Selected Proposal Title: Identifying Trends in the Nanoscale Interactions between Noble Metal Dopants and Fe Oxide Surfaces which Predict Dopant Hydrodeoxygenation Activity

Postdoctoral Projects: “Hydrodeoxygenation of Phenolics at Solvent-Metal Interfaces: Enabling New Catalytic Pathways by Modifying the Reactive Hydrogen Species”

Under supervision of Ya-Huei (Cathy) Chin, Department of Chemical Engineering and Applied Chemistry, University of Toronto (UofT)

“Low Temperature CO Oxidation with a Single Site Pt Catalyst Supported on Thin Film Cu Oxide: Elucidating the Chemical Nature of the Pt Active Sites”

Under supervision of Jean-Sabin McEwen, The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University (WSU)

PhD Dissertation: “Atomistic Elucidation of the Synergy within Noble Metal Promoted-Fe Catalysts for the Hydrodeoxygenation of Phenolic Compounds”

Under supervision of Jean-Sabin McEwen, The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University (WSU)

Research Experience:

My research focuses on the atomistic level chemical properties of solid surfaces, specifically, how the local environment―i.e. surface structure and chemical composition as well as solvent-solid interfaces―influences the macroscopic catalytic performance for energy and environmental applications. Atomistic insight is critical for discovering new materials and chemistry and for tuning the reactivity and selectivity of homogeneous and heterogeneous catalysis in both vapor and condensed phases. To this end, I specialize in the merging of computational catalysis techniques (e.g. density functional theory, transition state theory, coverage dependent model construction, and molecular dynamics) with spectroscopy (e.g. x-ray photoelectron, infrared, Raman, and nuclear magnetic resonance), scanning tunneling microscopy, and kinetics (e.g. rate dependencies and isotopic effects). An example of the power of such a combined computational and experimental approach can be seen in my work developing Pt single atom supported catalysts for lower temperature CO oxidation, a reaction key to reducing automotive emissions during the cold start-up period. I was able to unambiguously show that single Pt atoms supported on thin film Cu oxides perform CO oxidation much more efficiently than more traditional catalysts and at a much lower temperature range. Furthermore, I identified key chemical properties of the single atoms and support material that lead to their enhanced catalytic performance, providing a clear path forward for the development of highly economic single atom catalysts. This research approach allows me to precisely decipher the nature of catalytically active sites, determine the effect of solvent-surface interfaces, and identify reactive intermediates through detailed quantum chemical analyses. Thus far, I have published 26 peer reviewed papers with over 700 citations.

Teaching Interests:

My teaching interests lie in exposing chemical engineering graduate students to the experimental and theoretical principles and tools that allow us to probe and control atomistic level chemical phenomena. Using my time as a postdoc at WSU as an example, I noticed that the majority of entering chemical engineering graduate students never had a full course on quantum mechanics and other advanced topics. Knowledge of such topics is crucial to correctly interpreting computational, spectroscopic, and kinetic results. To address this need, I developed and taught a “Fundamentals in Atomistic Computational Methods” course covering the foundational principles of quantum mechanics, atomistic modeling theory, statistical mechanics, and solid state physics. This course was taught at WSU in the Spring 2018 semester and combined theoretical principles with practical applications in the form of molecular model construction and simulation for catalytic reactions. Students were evaluated based on four written exams and a final oral exam. The development of this course gave me much needed hands-on experience in the preparation and implementation of graduate level classes.

One of the most challenging and enjoyable aspects of my time in academia has been mentoring junior scientists on original research projects. Watching a new student grow beyond the rote memorization of a subject to a deep understanding is immensely gratifying. During my time at WSU, I directly mentored six graduate students and four undergraduates from four different countries. These students have authored or co-authored nine publications and given 16 presentations on their original research. As a woman in STEM myself, the support and female representation from my undergraduate advisor and UofT postdoctoral supervisor was critical to my success and I found it very rewarding to in turn do the same for two female graduate students and three female undergraduate students.

Service Experience:

It is a fundamental belief of mine that anyone can become a scientist or engineer if given sufficient support, tools, and opportunities, and I have worked to improve representation in STEM fields through my outreach and volunteerism. I was a project judge for WSU’s Imagine Tomorrow for 3 years and an event organizer and judge for Science Olympiad for 8 years. These one-day events are regional and national STEM design- and research-competitions that together reach 16,000 middle and high school students annually across the United States. Through these activities, hundreds of middle and high school aged women have directly been exposed to my leadership and presence during these activities as they explored scientific thought, inquiry, and research. In this way, they have been able to see that a career in STEM is eminently achievable for themselves.

Selected Publications:

Hensley, Alyssa J.R.; Collinge, G.; Wang, Y.; McEwen, J.-S., Coverage-Dependent Adsorption of Hydrogen on Fe (100): Determining Catalytically Relevant Surface Structures via Lattice Gas Models. The Journal of Physical Chemistry C 2020, 124, 7254-7266.

Therrien, A.J.; Hensley, Alyssa J.R.; Marcinkowski, M.D.; Zhang, R.; Lucci, F.R.; Coughlin, B.; Schilling, A.C.; McEwen, J.-S.; Sykes, E.C.H., An Atomic-Scale View of Single-Site Pt Catalysis for Low-Temperature CO Oxidation. Nature Catalysis 2018, 1, 192-198.

Hensley, Alyssa J.R.; Wang, Y.; Mei, D.; McEwen, J.-S., Mechanistic Effects of Water on the Fe-Catalyzed Hydrodeoxygenation of Phenol - The Role of Brønsted Acid Sites. ACS Catalysis 2018, 8, 2200-2208.

Hensley, Alyssa J.R.; Wang, Y.; McEwen, J.-S., Phenol Deoxygenation Mechanisms on Fe (110) and Pd (111). ACS Catalysis 2015, 5, 523-536.

Hensley, Alyssa J.R.; Hong, Y.; Zhang, R.; Zhang, H.; Sun, J.; Wang, Y.; McEwen, J.-S., Enhanced Fe₂O₃ Reducibility via Surface Modification with Pd: Characterizing the Synergy within Pd/Fe Catalysts for Hydrodeoxygenation Reactions. ACS Catalysis 2014, 4, 3381-3392.