(6cf) Understanding and Controlling Multielectron Transfer Chemistry for Sustainable Energy Technologies

The synthesis of fuels and chemicals from sustainable feedstocks and energy sources is one of the crucial challenges we face today. The coupling of renewable electricity sources, such as solar or wind, to the generation and interconversion of economically and environmentally relevant products (e.g. hydrogen, ammonia, methanol) is an intriguing prospect but requires the careful coupling of electrical energy to chemical reaction.

Electrochemical methods offer a powerful method for promoting reactivity. A change in the driving force of a reaction that would require the application of hundreds of atmospheres of pressure can be achieved with less than a volt of applied potential. However, control over the driving force of a reaction does not necessarily come concurrently with control over the selectivity of the electron transfer. A multitude of products, as well as catalyst and conductive support corrosion, are often observed during electrochemical reactions, limiting the efficiency of the desired process. With this in mind, the overarching goal of my research be to understand and promote efficient and selective photo- and electrochemically-driven multielectron transfer reactions with an emphasis on understanding how electrocatalyst surface chemistry and electrolyte conditions influence the efficiency and selectivity of the reaction.

My specific aims will be toward improved understanding and enhanced efficiency of electrochemical transformations involving nitrogen-based species (e.g., NO₃^-, NO_x, N₂), including the reduction of nitrates as well as both the reduction and oxidation of N₂. The nitrogen cycle plays a pivotal role in maintaining the health of our planet and society, and the efficient, sustainable interconversion of these species would have exciting applications in a range of fields, including commodity chemical synthesis, fuel generation, and environmental remediation. We will rationally develop novel catalytic materials and electrolytes for these reactions, and the relationship of catalyst surface structure to performance will be characterized by careful ex situ and in operandostudy. These new electrocatalysts will then be integrated into device structures to evaluate them under practical conditions, and the performance of these devices, both with respect to catalyst activity and stability, will inform the development of the next generation of new catalysts. As our understanding of the fundamentals of the reduction/oxidation of nitrogen species evolves over time, we will couple these reactions to photoactive materials to develop solar-powered devices that can be readily deployed without external power sources. This cyclic strategy of catalyst design, characterization, and device integration should drive us to progress both fundamentally and practically toward real-world solutions to challenging problems in renewable energy, environmental chemistry, and other fields.

Teaching Interests:

My teaching experience includes the mentorship of multiple graduate and undergraduate students in the laboratory. Additionally, I have acted as the head instructor for advanced graduate courses in photoelectrochemistry during my PhD, and have served in teaching assistant roles. My training has prepared me to ably serve a Chemical Engineering department in the instruction of undergraduate and graduate students both in the laboratory and in the classroom. I feel immediately qualified to teach a range of undergraduate-level chemical engineering courses, including kinetics, thermodynamics, mass/energy balances, and other physical/analytical courses. In the future, I hope to have the opportunity to develop (1) a course directed toward graduate students and senior undergraduates aimed at understanding electrochemistry and its practical application to electrocatalysis of energy-rich molecules, as well as (2) a course designed around semiconductor electrochemistry, photoelectrochemistry, and applications to emerging renewable energy technologies.

Research Experience:

Postdoctoral Scholar 2016-Present

Department of Chemical Engineering, Stanford University

Advisor: Thomas F. Jaramillo

Project: Synthesis and Characterization of N₂Reduction Electrocatalysts

• Investigated the dependence of electrocatalytic NH₃production rate on electrolyte composition and catalyst identity
• Developed and applied analytical techniques and best practices for identifying electrochemically generated NH₃in non-aqueous electrolytes

Graduate Research Assistant 2010-2016

Division of Chemistry and Chemical Engineering, California Institute of Technology

Advisor: Nathan S. Lewis

Ph.D. Thesis: Chemical and Photoelectrochemical Behavior of Graphene-Covered Silicon Photoanodes

• Investigated the chemical and photoelectrochemical stability of Si and GaAs photoelectrodes covered by atomically thin graphene layers in aqueous electrolytes
• Explored the effect of graphene interfacial layers on the electronic properties of silicon/electrolyte junctions related to solar cell device performance
• Developed methods and classification scheme for the characterization of the efficiency of photoelectrochemical and photovoltaic solar-to-fuels devices

Undergraduate/Graduate Research Assistant 2005-2010

Department of Chemistry, University of Virginia

Advisor: W. Dean Harman

M.S. Thesis: Laying the Groundwork for a Tantalum Dearomatization Agent

B.S. Thesis: Synthesis and Application of an η²N-acetylpyridinium Complex

• Synthesized tungsten- and tantalum-based organometallic reagents used to modify and enhance the reactivity of stable aromatic arenes and pyridines
• Investigated the relationship between reactivity enhancement in aromatic ligands and electrochemical properties of the associated organometallic complex

2019 Calendar Year Publications (As of June 21, 2019)

1. Nielander, A.C.; McEnaney, J.;Schwalbe, J.; Baker, J.; Blair, S.; Wang, L.; Pelton, J.; Bent, S.; Cargnello, M.; Chorkendorff, I.; Jaramillo, T. A Versatile Method for Ammonia Detection in a Range of Relevant Electrolytes Via Direct NMR Techniques. ACS Catalysis 2019,9, 5797-5802.

2. Andersen, S.; ÄŒolić, V.; Yang, S.; Schwalbe, J.; Nielander, A. C.; McEnaney, J.; Enemark-Rasmussen, K.; Baker, J.; Singh, A.; Rohr, B.; Statt, M.; Blair, S.; Mezzavilla, S.; Kibsgaard, J.; Vesborg, P.; Cargnello, M.; Bent, S.; Jaramillo, T.; Stephens, I.; Norskov, J.; Chorkendorff, I. Assessing the Current State of Catalyst Development for the Electrochemical Reduction of N₂to NH₃. Nature 2019,DOI: 10.1038/s41586-019-1260-x.

3. Hellstern, T.*; Nielander, A.C.*; Chakthranont, P.*; King, L.A.; Willis, J.; Xu, S.; MacIsaac, C.; Hahn, C.; Bent, S.; Prinz, F.; Jaramillo, T.F. Nanostructuring Strategies to Increase the Photoelectrochemical Water Splitting Activity of Silicon Photocathodes.ACS Applied Nano Materials 2019,2(1) 6-11.

4. Wang, L.; Nitopi, S.; Wong, A.; Snider, J.; Nielander, A. C.; Morales-Guio, C.; Orazov, M.; Higgins, D.; Hahn, C.; Jaramillo, T. Directing Selectivity in Catalysis with Surface Area: Electrochemically Converting Carbon Monoxide to Liquid Fuels. Nature Catalysis 2019, DOI: 10.1038/s41929-019-0301-z.

5. Boyd, M.; Latimer, A.; Dickens, C.; Nielander, A.C.; Hahn, C.; Higgins, D.; Jaramillo, T. Electro-Oxidation of Methane on Platinum Under Ambient Conditions. ACS Catalysis, Accepted, Jun 19 2019.