(6ec) Energy Storage and Conversion with Organic Molecules and Advanced Porous Electrodes

Enabling renewable energy technology is critical for reducing carbon emissions and mitigating the harmful effects of climate change. Broadly, my research has sought to understand and apply electrochemical engineering principles to develop and improve energy storage and conversion technologies, with the ultimate goal of making a clean energy future possible. By combining electrochemical characterization of materials, flow cell experiments, and multi-scale simulation, a deeper understanding of the interplay between mass transport and electrochemical kinetics can be gained within these devices.

As a faculty member, I plan to study the electrochemical properties of organic molecules, such as quinones, and their use in energy storage and conversion devices. Quinone electrochemistry is particularly interesting because their electrochemical properties can be tuned by attaching different functional groups to the molecule. This feature opens up a wide range of new redox couples, with applications in energy storage and carbon-dioxide sequestration. The effect of various substituents on the reduction/oxidation mechanism of these molecules is not well understood, but critical for identifying possible kinetic limitations and extending battery lifetime. Through a combination of half-cell electrochemical characterization, simulation, and full-cell experiments, my research will develop a fundamental understanding of reduction/oxidation pathways in these molecules. This knowledge will be harnessed both to improve the efficiency and lifetime of flow batteries and to explore new applications, such as electrochemical synthesis.

I am also interested in studying the role of porous electrode flow cell devices for energy storage and conversion applications. Flow batteries, fuel cells, and electrolyzers have immediate applications in decarbonizing our economy and rely on carefully engineered porous electrodes. The proper structure and design of a porous electrode for flow batteries, for example, is not well known, yet many electrochemical couples are so kinetically facile that mass transport within the electrode is the greatest hindrance to flow battery operation at high current. My research will use simulation and flow-cell experiments to establish connections between porous electrode structure, mass transport, and performance to enable high-current operation of electrochemical flow devices.

In summary, I plan to advance understanding of electrochemical kinetics and mass transport within porous electrodes to improve flow battery efficiency and lifetime, and apply the knowledge gained to energy conversion applications such as hydrogen production and electrochemical synthesis.

Teaching Interests:

I have served as a teaching assistant for two courses: Introduction to Solid-State Chemistry, a freshman-level general chemistry course for materials scientists, and Engineering Thermodynamics, a junior and senior level course for engineering students. I have taught in both traditional classroom and large-scale online format courses, with responsibilities including lecturing, course organization, problem set and exam design, grading, and running a laboratory class session. Furthermore, as a participant in the Harvard Departmental Teaching Fellow program, I took and later co-taught a pedagogy course for science and engineering, as well as participated in biweekly seminars on best teaching practices.

I am interested in applying active learning strategies in my classroom to improve student engagement and retention of information. This could take the form of low-stakes, multiple-choice questions followed by a short discussion between students sitting next to each other, which has been shown to help students arrive at the correct answer to a particular question. Reserving a few minutes at the end of each class period for students to reflect on and write about what they’ve learned and what still confuses them can also help encourage learning, and is useful feedback to the instructor as well. On an individual student basis, and as a research mentor, I ask a lot of questions, in an effort both to gauge the student’s understanding of particular material and to help push them to understand new material.

Mathematical modeling is a powerful teaching tool, because it integrates programming, mathematics, and science classes. A course on mathematical methods would give students important transferable skills, like computer programming and data analysis, and encourage discovery learning by allowing them to test hypotheses on how a system would operate. A question like “What happens if I raise the temperature?”, for example, moves from a lengthy experiment to a few keystrokes. Thus, one of the courses I plan to develop is a mathematical modeling in electrochemistry course, which would allow interested students to build models to tackle questions like these. Such a course could also build upon concepts covered in core chemical engineering classes including transport, kinetics, and thermodynamics.

Research Experience:

Postdoctoral Scholar, Lawrence Berkeley National Laboratory, 2017 – present

Advisor: Adam Weber

• Developed a multiphysics computational model of anion-exchange membrane fuel cells to understand the role of water transport and carbon dioxide contamination in cell performance.
• Developed anion-exchange membrane electrolyzer model and advised undergraduate researcher to illustrate effects of electrolyte composition.
• Simulated water transport and hydrogen crossover in small-scale, passive-water-management fuel cell systems, including sub-freezing operation.

Graduate Student, Applied Physics, Harvard School of Engineering and Applied Sciences, 2012 – 2017

PhD thesis: Topics in the Development of Aqueous Quinone Flow Batteries

Advisor: Michael Aziz

• Characterized electrochemical properties of several organic molecules for energy storage applications via cyclic voltammetry and rotating disk electrode studies.
• Combined simulation and electrochemical characterization to suggest a reduction mechanism for 2,6-dihydroxyanthraquinone. This information was later used to identify decomposition mechanisms.
• Demonstrated the effects of chemical substituents on operating voltage, efficiency, and lifetime of organic-molecule-based flow batteries by designing, machining, and operating lab-scale flow battery for charge/discharge cycling.
• Simulated electrochemical and fluid dynamic phenomena in flow battery with analytical and finite element computational techniques to understand the role of mass transport in flow battery performance.

Selected Publications:

M.R. Gerhardt, L.M. Pant, and A.Z. Weber. Along-the-Channel Impacts of Water Management and Carbon-Dioxide Contamination in Hydroxide-Exchange-Membrane Fuel Cells: A Modeling Study. Journal of the Electrochemical Society, 166(7):F3180-F3192, 2019.

M.R. Gerhardt, A.A. Wong, and M.J. Aziz. The Effect of Interdigitated Channel and Land Dimensions on Flow Cell Performance. Journal of the Electrochemical Society, 165(11):A2625-A2643, 2018.

Q. Chen, M.R. Gerhardt, and M.J. Aziz. Dissection of the Voltage Losses of an Acidic Quinone Redox Flow Battery. Journal of the Electrochemical Society, 164(6):A1126-A1132, 2017.

M.R. Gerhardt, L. Tong, R. Gómez-Bombarelli, Q. Chen, M.P. Marshak, C.J. Galvin, A. Aspuru-Guzik, R.G. Gordon, and M.J. Aziz. Anthraquinone Derivatives in Aqueous Flow Batteries. Advanced Energy Materials, 3:1601488, 2016.

Q. Chen, M.R. Gerhardt, L. Hartle, and M.J. Aziz. A Quinone-Bromide Flow Battery with 1 W/cm² Power Density. Journal of the Electrochemical Society, 163(1):A5010–A5013, 2015.

K. Lin, Q. Chen, M.R. Gerhardt, L. Tong, S.B. Kim, L. Eisenach, A.W. Valle, D. Hardee, R.G. Gordon, M.J. Aziz, and M.P. Marshak. Alkaline quinone flow battery. Science, 349(6255):1529–1532, 2015.

B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon, and M.J. Aziz. A metal-free organic–inorganic aqueous flow battery. Nature, 505(7482):195–198, 2014.