(4jj) Tailoring Microenvironments for the Microscopic to Macroscopic Design of Decarbonized Conversion and Separation Processes

The development of technologies capable of utilizing waste greenhouse gas streams for chemical conversion will be key to creating a sustainable future. Electrochemical conversion has emerged as a sustainable, electrified process capable of generating valuable chemical commodities from industrial waste streams. An inherent need for sustainable conversion technologies is optimized, energy efficient separations processes. Currently, separations technologies operate with low energy efficiency and account for 40 – 60% of the energy and capital cost of a chemical plant. Hence, the co-design of sustainable chemical conversion processes and complementary low-energy separations technologies is a critical area of future research. To achieve improvements in energy efficiency and performance at the macroscopic scale requires an understanding of the microscopic phenomena which dictate performance. Many of these systems operate under conditions where factors such as water and ion transport, local pH, and solvation and electric double layer structure exert significant influence on performance. I am interested in developing characterization techniques to investigate the microenvironments of aqueous conversion and separations processes. Correlating this microscale characterization to macroscopic performance will enable the efficient co-design and integration of chemical conversion and separation technologies capable of utilizing industrial waste streams to generate valuable, purified chemical products.

Research Experience

As a faculty member, I plan to build upon the experimental skills I developed during my doctoral studies at Stanford University working with Dr. Adam Nielander and Prof. Thomas Jaramillo. During my Ph.D., I investigated the integration of photovoltaic drivers and electrochemical systems for the unassisted, solar-driven generation of valuable chemicals. Some key highlights of this research include:

• I designed a tandem, solar-driven electrochemical-thermocatalytic process for the direct, unassisted conversion of CO₂ to butene. This process involved the co-design and integration of the gaseous product stream of a photovoltaic-electrochemical CO₂R reactor to a thermocatalytic ethylene oligomerization reactor.
• I established operando inductively-coupled plasma mass spectrometry methods for assessing the simulated diurnal stability of (photo)electrocatalysts for the hydrogen evolution and CO₂R reactions. Coupled to ex-situ characterization methods, including Raman spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy, I proposed a mechanism for the redox-driven corrosion of protective thin films for photocathodes.
• Through the combination of experimental methods, real-world meteorological data, and computational methods, I developed a potential and temperature dependent model to predict the diurnal behavior of solar-driven Cu-based CO₂ The model is scaled from the mw to MW operating scale, and from analysis of a single day to an annual cycle to simulate the performance of scaled, solar-driven Cu-based CO₂R systems at various locations across the globe.

Leveraging existing methods and theories in electrochemical and photovoltaic research, my work has investigated the timescales which arise when operating electrochemical solar fuels reactors under diurnal conditions. Using a combination of in situ experimental techniques, ex situ analysis, and computational modeling, my doctoral work has begun to tackle some of the unique performance and material challenges which arise under diurnal operating conditions towards the larger scale implementation of electrochemical solar fuels technology.

Future Research

My research group will integrate multi-length and timescale characterization techniques to study solid-liquid and liquid-liquid interfaces to tackle the challenge of integration for electrocatalytic conversion and liquid-liquid separation processes. In electrochemical systems, the role of water transport and water structure at the catalyst-electrolyte interface can steer selectivity of multi-product reactions. By tuning water and ion transport using polymeric thin films and separators, we will investigate the role of the electric double layer structure for electrochemical systems derived from greenhouse gas streams, focusing on CH₄ and CO₂ feedstocks. With the goal of separating miscible organic products from the aqueous phase, we will develop experimental methods to characterize the hydration and solvation shell structure on salt-induced liquid-liquid phase separation. Our initial goal will be to investigate different ionic salts for alcohol-water separations to identify structural descriptors which translate to improved separations efficiency. To probe the dynamic behavior during these conversion and separation processes, we will develop spectroscopic techniques, coupled to synchrotron experiments, including x-ray scattering and neutron reflectometry. These techniques will provide microscopic information regarding the reaction and/or separation microenvironment and will be coupled to conversion and separation performance to establish the key driving factors for improved macroscopic performance.

Teaching Interests

My motivation in pursuing a faculty career lies in providing the next generation of scientists with the opportunities and mentorship which I have been privileged enough to receive during my academic journey. During my undergraduate and graduate career, I have taken steps to create teaching pathways and engagement programs to help students from diverse backgrounds pursue their goals in STEM. As an undergraduate at Rutgers University, I was a tutor for student-athletes pursuing STEM degrees and a learning assistant for the Chemical Engineering courses, (i) Material and Energy Balances and (ii) Design and Separation Processes. At Stanford, I have expanded my teaching experience beyond the undergraduate level, serving as a teaching assistant for two years for the graduate course, Fundamentals and Applications of Spectroscopy, and tutoring high school sophomores in Chemistry and Calculus. I believe that encouraging diversity in STEM begins with creating pipelines for underrepresented minorities to STEM programs as early as high school. To this end, I created the Stanford Summit Tahoma Expedition Program (SSTEP), an 8-week internship program with Summit Tahoma, a Hispanic serving public charter school in San Jose, in 2022. In this program, juniors and seniors shadow multiple Stanford researchers for 8 weeks to develop professional scientific skills and to learn about careers in STEM. As a faculty member, I plan to continue establishing lasting pathways, such as the SSTEP program, to ensure that any student interested in pursuing a career in STEM has access to the resources they need to help them succeed.

My education as a chemical engineer has prepared me to teach the core courses at the undergraduate and graduate level; however, my previous experiences have uniquely positioned me to teach thermodynamics and separations. Throughout my career, I also hope to develop my own courses to educate the next generation of scientists and engineers. Some courses I am interested in developing include, (i) an undergraduate-level course on the integration of renewable energy and chemical conversion technologies (e.g., electrochemistry, thermal catalysis), and (ii) a graduate level course on the role of interfacial phenomena in chemical conversion and separation. As a student, I have valued interdisciplinary courses which relate fundamental theory with real-world applications, and I hope to use this guiding principle as one of my teaching philosophies in the future. My past teaching experience has shown me that students retain and apply knowledge more effectively when they can relate the principles they learn to the everyday environment they are in. Hence, my teaching style emphasizes learning and application of knowledge by creating an active environment where students are encouraged to develop the ability to ask critical questions, learn to problem solve, and translate the theory they learn to its application in the world around them.

Selected awards

• MIT Rising Stars in Chemical Engineering, 2024
• CAS Future Leaders, 2024
• Stanford Chemical Engineering Service Leadership Award, 2023
• Stanford Chevron Energy Fellowship, 2023 – 2024
• Stanford Diversifying Academia, Recruiting Excellence Fellowship, 2023 – 2025
• Stanford JEDI Initiative Funding Award, 2023
• Stanford Community Impact Award, 2023
• Herbert and Pauling Goodkind Endowed Scholarship, 2017
• James Dickson Carr Scholarship, 2016

Selected publications

1. Yap, K. M. K.^*; Wei, W. J.^*; Rodríguez Pabón, M.; King, A. J.; Wei, L.; Lee, S.; Bui, J.; Weber, A. Z.^‡,; Bell, A. T.^‡; Nielander, A. C.^‡; Jaramillo, T. F.^‡; Modeling Diurnal and Seasonal Ethylene Generation from Solar-Driven Electrochemical CO₂ Reduction Devices. Energy & Environmental Science. 2024, https://doi.org/10.1039/D4EE00545G.
2. Yap, K. M. K.; Lee, S.; Steiner, M. A.; Emily, L.; Nielander, A. C.; Jaramillo, T. F.; Yap, K. M. K.; Lee, S.; Steiner, M. A.; Avile, J. E. A Framework for Understanding Efficient Diurnal CO 2 Reduction Using Si and GaAs Photocathodes. Chem C 2023, 3 (6). https://doi.org/10.1016/j.checat.2023.100641.
3. Calvinho, K. U. D.^*; Alherz, A. W.^*; Yap, K. M. K.^*; Laursen, A. B.; Hwang, S.; Bare, Z. J. L.; Clifford, Z.; Musgrave, C. B.^‡; Dismukes, G. C.^‡; Surface Hydrides on Fe2P Electrocatalyst Reduce CO2 at Low Overpotential: Steering Selectivity to Ethylene Glycol. Journal of the American Chemical Society, 2021, 143, 50, 21275-21285.
4. Yap, K. M. K.^*; Aitbekova, A.^*; Salazar, M.^*; Kistler, T.; Rodríguez Pabón, M.; Su, M. P.; Watkins, N. B.; Lee, S.; Agbo, P.; Peters, J. C.^‡; Agapie, T.^‡; Nielander, A. C.^‡; Atwater, H. A.^‡; Jaramillo, T. F.^‡; Bell, A. T.^‡; A Tandem Photovoltaic-Electrochemical Photothermal Process for CO₂ Conversion to Butene. 2024, In Preparation.
5. Yap, K. M. K.^*; Lee, S. A.^*; Jaramillo, T. F. ^‡; Xiang, X.^‡; Nielander, A. C.^‡. Challenges for the diurnal operation of electrochemical solar fuels technologies. 2024, In Preparation.