(4cn) Electrochemical Systems for Sustainable Energy: Solid Oxide Electrocatalytic Cells and Lithium-Ion Batteries

Electrochemical systems for energy conversion and storage are expected to play a critical role in the decarbonization of the energy sector by supporting the integration of renewable energy sources. Solid oxide electrocatalytic cells (SOECs) and lithium-batteries (LIBs) not only facilitate replacing energy-intensive chemical processes, but also enable the storage of excess electrical energy in the form of chemicals. My research is dedicated to developing a fundamental understanding of electrocatalytic processes to overcome the challenges on this path to sustainability.

Research Vision

Electrochemical systems with SOECs have the potential to enable the large-scale conversion and storage of renewable energy in the form of chemicals. SOECs create an ideal environment for the co-electrolysis of H₂O and CO₂ to produce H₂ and CO, known as syngas. The high operating temperatures enable efficient energy conversion with nearly 100% Faradaic efficiency and allow for an optimal H₂/CO ratio suitable for subsequent processes, such as the Fischer-Tropsch reaction. Additionally, SOECs offer an excellent reaction environment with solid electrolytes, acting as membrane reactors with high selectivity for the production of light alkenes through oxidative dehydrogenation (ODH) of ethane/propane or oxidative coupling of methane (OCM), as well as the production of ammonia at ambient pressure. Thus, they can provide efficient reaction routes alternative to the traditional energy-intensive processes. A major challenge in SOECs is enhancing the electrocatalytic activity of electrode materials while maintaining their stability at high operating temperatures. Perovskite oxide is one of the promising candidates as an electrode material providing catalytic activity and electronic and ionic conductivity. However, they still fall short compared to Ni/YSZ, the state-of-the-art commercial electrode material, in terms of overall stability and electrochemical activity. Developing novel perovskite electrodes for SOECs requires comprehensive knowledge of materials synthesis, device engineering, operando electrochemistry, and spectroscopy, along with a physical understanding of the electrochemical processes involved.

My research group will leverage electrochemical engineering principles and a physical understanding of electrochemical processes to develop a novel electrode catalyst with superior activity and stability. These catalysts would be effectively applicable to energy-efficient SOECs for diverse reactions, such as electrolysis of H₂O and CO₂, light alkene production, and ammonia synthesis, thereby accelerating the transition to a sustainable future. We will investigate exsolution, where metals migrate within the perovskite lattice to form metallic nanoparticles on the surface, using both thermochemical and electrochemical methods. Despite its significant impact on electrochemical activity, there remains a gap in understanding the underlying processes. Our goal is to establish a comprehensive understanding of the electrochemical mechanisms that influence exsolution and to develop novel electrode catalysts that activate electrochemical reactions. Furthermore, we will develop physical models to simulate the electrochemical processes occurring in SOECs at high operating temperatures, which complicate the characterization of electrodes during operation. This integrated approach will provide fundamental insights into exsolution and electrochemical reactions, aiding the development of novel electrode materials with enhanced activity and stability. The advancements in electrochemical science from our research will benefit SOECs for various chemical reactions, which are currently carried out energy-intensive processes. My unique expertise in experiments and modeling related to SOECs and electrochemical processes positions me advantageously to address these challenges.

In addition, I envision electrochemical energy conversion and storage for grid-scale application using (LIBs). Over the past two decades, the costs of renewable energy production and LIBs have decreased by over 90%, enabling the electrification of the energy sector. Global warming and rising temperatures pose severe threats to future societies, necessitating immediate and innovative reductions in greenhouse gas emissions. LIBs are currently the readily deployable technology capable of achieving this. While renewable energy and LIB technologies are technically prepared, their potential as energy storage devices is not being fully realized. This is primarily because LIB research has been predominantly focused on the transportation sector. However, for the electrification of industry and buildings, utilizing LIBs as energy storage devices is essential. Many simulation studies highlight the potential of LIBs as energy storage devices, but there is a lack of publicly available experimental performance tests. Consequently, LIBs are not being adequately utilized as energy storage devices. Therefore, my research group will aim to enhance the performance, safety, and lifespan of LIBs and to disseminate research findings to promote their application in industrial and building sectors.

Research Experience

Postdoctoral advisor: Dr. Fikile Brushett, Massachusetts Institute of Technology

Graduate advisor: Dr. Umit Ozkan, The Ohio State University

Through my graduate and postdoctoral research, I have delved into the fundamental aspects of solid electrochemistry, SOECs, LIBs, and perovskite using both experimental techniques and physics modeling.

I investigated thermochemical exsolution on ferrite-based perovskites to enhance their electrocatalytic activity and stability for applications such as electrolysis of H₂O and CO₂, OCM, ODH, and ammonia synthesis under ambient pressure. By doping nickel or cobalt atoms on the ferrite-based perovskite and inducing exsolution through a thermochemical process, exposure to a reducing gas such as hydrogen or methane, I explored the effects of temperature, exposure duration, and partial pressure of the reducing gas on the exsolution. The resultant improvements in electrocatalytic activity were evaluated using a suite of microscopic, spectroscopic, and electrochemical methods, both pre- and post-reaction. Exsolution significantly improved electrocatalytic activity by modulating adsorption characteristics, electron transfer, and the electronic states of catalytically active atoms.

I also explored the electrochemical exsolution of metal nanoparticles from perovskite during electrolysis. This process can be triggered by applying cathodic polarization to the perovskite oxide electrode for less than two minutes. This is in stark contrast to thermochemical exsolution, which requires a minimum of several hours to achieve. I studied the electrochemical behavior of exsolution by scanning the cell voltage within the cathodic polarization window, identifying the electrochemical switching point as the transition from increasing to decreasing area-specific resistance. Additionally, I developed a custom-designed operando X-ray absorption spectroscopy cell to observe the edge energy change and exsolution of B-site atoms during electrolysis.

Based on my experimental works on SOECs, I realized the necessity of multi-physics simulations to fundamentally understand the chemical/physical processes occurring simultaneously in SOECs. As a postdoctoral associate at MIT, I am actively working on multi-physics modeling of SOECs for various reactions and exsolution. I am developing a multi-physics model for electrochemical OCM, considering the complexity of different reactions involved. The novel simulation model aims to identify critical parameters affecting selectivity and to design an effective reactor. Moreover, I am working on electrochemical exsolution and its effect on the co-electrolysis of H₂O and CO₂. This simulation model will provide fundamental understanding on the electrochemical exsolution process, which cannot be fully explored experimentally.

Moreover, I investigated the performance and durability of different commercial 18650 LIBs as a function of both calendar aging at different states-of-charges (SOCs) and duty cycles representative of an energy arbitrage use-case. I seek to establish connections between subtle changes in performance and chemical and physical evolutions of cell components, contributing to the understanding of how operational conditions and reaction chemistries influence battery degradation. I developed battery testing protocols for energy arbitrage based on representative electricity prices, derived from real-world data sets, for different seasons and regions of the US. I then test sets of cells under these cycling conditions to determine how key figures of merit change. My findings indicate that battery performance is sensitive to cycling and to resting at high states-of-charge but, largely insensitive to charging rates (C/3 to C/20), at least for the chemistries considered. This suggests that while high SOCs accelerate degradation, moderate variations in charging rates do not significantly impact the overall performance of the LIBs.

Teaching Interests

I am eager to instruct both undergraduate and graduate courses in engineering mathematics, numerical analysis, electrochemistry, thermodynamics, heat and mass transfer, catalysis, and fuel cells. My teaching philosophy centers on fostering a deep understanding of fundamental principles while encouraging practical application through hands-on learning and real-world problem-solving.

I am particularly enthusiastic about offering an advanced electrochemistry course focused on solid electrochemistry as it pertains to SOECs. This course will cover critical topics such as electrochemical reactions at the three-phase boundary and the effects of electric polarization on current distribution. Students will explore modeling of charge transfer kinetics and thermodynamics, along with cutting-edge electrochemical and operando techniques. Practical laboratory sessions will provide hands-on experience in learning and interpreting common electrochemical methods, thereby bridging theoretical knowledge with practical skills.

Furthermore, I envision teaching specialized courses on energy conversion and storage, offering comprehensive overviews of key transport phenomena in electrochemical systems. These courses will delve into the fundamental principles and applications of electrochemical energy conversion and storage technologies, including solid oxide electrolysis cells (SOECs) and secondary batteries. Students will gain insights into the chemical and physical processes involved, preparing them for careers in the field of sustainable energy technologies.

To enhance the learning experience, I plan to incorporate project-based learning, where students tackle real-world challenges related to energy conversion and storage. This approach will not only deepen their understanding but also develop their problem-solving and critical-thinking skills. Additionally, I aim to foster a collaborative learning environment by encouraging interdisciplinary projects and discussions, reflecting the multifaceted nature of modern engineering problems.