KNI Special Seminar: Developing A Tandem Photoelectrochemical/Photothermal System for CO2 Reduction to Liquid Fuels

Join the Kavli Nanoscience Institute on Tuesday, September 5 at 3 pm for a special seminar by KNI Prize Postdoctoral Scholar Dr. Aisulu Aitbekova. Dr. Aitbekova's talk will describe her work on developing a photoelectrochemical-photothermal system capable of converting carbon dioxide, sunlight and water into desired multicarbon products for solar fuels.

NOTE LOCATION CHANGE: The seminar will take place in 106 Spalding Laboratory. A light reception will follow the seminar in the Spalding Lobby.

Developing A Tandem Photoelectrochemical/Photothermal System for CO2 Reduction to Liquid Fuels

Aisulu Aitbekova¹, Kyra Yap², Matthew Salazar¹, Magel Su¹, Tobias A. Kistler³, Peter Agbo³, Theodor Agapie¹, Jonas C. Peters¹, Thomas F. Jaramillo², Alexis T. Bell³, Harry A. Atwater¹

¹Division of Engineering and Applied Science, California Institute of Technology, Pasadena, 91125, CA, USA

²SLAC National Accelerator Laboratory, Menlo Park, 94025, CA, USA

³Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, 94720, CA, USA

Generating solar fuels for difficult-to-electrify areas (such as long-distance transportation) necessitates the development of technologies optimized at multiple levels. On a molecular level, we need to create catalytic materials that stably convert CO2 with high conversion rates and selectivity to desired products. On a system level, we need to engineer reactors that efficiently convert solar energy into heat required to run chemical reactions. This stringent requirement explains a lack of studies reporting the formation of liquid fuels. We have developed a two-step photoelectrochemical-photothermal system that converts CO2, water, and sunlight into multicarbon products.

In the first step of the process, CO2 reduces to ethylene in a photoelectrochemical cell. Here we focus on a catalyst design and show how functionalizing a copper electrode with molecular additives enhances ethylene formation and suppresses the generation of unwanted hydrogen. The working hypothesis for this selectivity change is the inhibited proton transfer through hydrophobic molecular additive films, which results in diminished hydrogen evolution reaction rates.

In the second step, ethylene oligomerizes into butenes and hexenes inside a photothermal reactor with a selective solar absorber. Operating such a reactor under sunlight requires maximizing the light-to-heat conversion and minimizing heat losses. We accomplish this goal by simultaneously optimizing the absorber's optical properties, the reactor's geometry, and insulation. The optimized reactor reaches a temperature of 120 °C (under 3-sun intensity), sufficient to drive an industrially relevant ethylene oligomerization reaction to convert ethylene into liquid fuels. Moreover, we demonstrate that this process works with a dilute ethylene stream gas produced by the photoelectrochemical cell. We have developed a novel framework to generate solar fuels through catalyst design and reactor engineering.

Bio

Aisulu is a Kavli Nanoscience Institute Postdoctoral Fellow in Harry A. Atwater's research group and a Liquid Sunlight Alliance DOE Energy Innovation Hub member. Before joining Caltech, she earned her Ph.D. in Chemical Engineering at Stanford University. Aisulu received her M.S. in Chemical Engineering Practice from the Massachusetts Institute of Technology and B.S. in Chemical Engineering from Nazarbayev University in Kazakhstan. Her current research focuses on developing novel processes to convert CO2, water, and sunlight into liquid fuels. Outside the lab, Aisulu leads and participates in outreach initiatives. At Caltech, she has established an Accountability Partners Program to help undergraduate students from diverse backgrounds apply to graduate school.