Bruce E. Koel, professor of chemical and biological engineering (CBE), transferred to emeritus status on July 1, 2024. Born in Norton, Kansas, in 1955, Bruce was the first in his family to attend college. His journey to becoming a pioneering figure in surface science and catalysis is a testament to his dedication and innovative spirit. His work has made significant contributions to the effort to lower greenhouse gas emissions, conserve materials, and curb the effects of climate change.

Bruce has had a career that includes many institutional affiliations, with Princeton as the setting of only his final chapter as an academic. His time at Princeton has been marked by excellence in research, teaching, leadership, and service. When he joined the Princeton faculty in 2011 as a professor of chemical and biological engineering, he also established two new materials characterization and surface chemistry laboratories at the Princeton Plasma Physics Laboratory (PPPL), the only such laboratories at this Department of Energy National Laboratory, which Princeton manages. While at Princeton and PPPL, his wide-ranging research activities included plasma-materials interactions for high-temperature fusion plasmas, essential for fusion energy research and future fusion reactor design; low-temperature, nonequilibrium plasma reactions, with applications in recycling lithium-ion battery materials and in powering catalytic synthesis of chemicals and fuels by renewable electricity rather than thermal processes; electrocatalysis and photocatalysis; nanoparticle coatings critical to environmental cleanup; and reactions over bimetallic catalysts. 

Bruce's academic foundation was laid at Emporia State University, where he received his bachelor’s and master’s degrees in chemistry in 1976 and 1978, respectively. He then earned his Ph.D. in chemistry from the University of Texas at Austin in 1981, where he began his foray into surface science. His time at the University of California, Berkeley, as a Miller Postdoctoral Fellow, furthered his expertise, especially in vibrational spectroscopy studies of adsorbed molecules.

Bruce’s first faculty position came in 1983 when he was appointed as an assistant professor in the chemistry department at the University of Colorado, Boulder, and as a fellow of the Cooperative Institute for Research in Environmental Sciences, where he carried out pioneering studies of nitrogen dioxide linkage isomerism, gold reactions with gases for environmental sensing, and established key concepts in bimetallic catalysis that are still influential today. Bruce received an Exxon Education Foundation Award and a Sloan Research Fellowship, and he was offered early tenure, unprecedented in his department at that time.

He moved to the University of Southern California (USC) in 1990 as an associate professor with tenure, where he was a founding member of the Laboratory for Molecular Robotics and published seminal research on the manipulation of nanoparticles using atomic force microscopy at ambient conditions. His time at USC was distinguished by wide-ranging research, including nanofabrication, ozone oxidation, C60 and superfulleride formation, barite dissolution, and atomic structures and reactivity of ultrathin metal films, alloys, and oxide surfaces. He was elected as a fellow of the American Physical Society in 1996, a fellow of the American Vacuum Society in 1999, and a fellow of the American Association for the Advancement of Science in 2004. His groundbreaking work using ordered alloy surfaces earned him the George A. Olah Award in Hydrocarbon or Petroleum Chemistry by the American Chemical Society in 2007. These studies revealed the differences in adsorbed molecule bonding and chemistry at such surfaces due to the presence of single atoms, two-atom, and three-atom sites at metal alloy surfaces, and demonstrated important aspects of geometric and electronic effects in alloy catalysis. He also served as chair of the Department of Chemistry at USC in the late 1990s.

In 2005, Bruce’s career took him to Lehigh University, where he conducted innovative studies on arsenic reactions in the utilization of iron nanoparticles for environmental cleanup. His administrative roles at Lehigh, including interim vice president and associate provost for research and graduate studies, showcased his commitments to leadership and service and to educating future generations of scientists and engineers.

At Princeton, Bruce pursued research built on his long history of investigating nonthermal chemistry and processes at surfaces using electron, ion, and radical beams to cause physical and chemical changes at surfaces. As a collaborator on both the National Spherical Torus Experiment and the upgraded Lithium Tokamak Experiment at PPPL, he developed and deployed translatable probes that can be used to expose material samples to fusion plasmas that then can be subjected to a variety of surface science measurements probing the adsorption, sputtering, and retention of deuterium in lithium films; the thermal stability of these films; and how contaminants affect these events. His work has provided critical insights into fundamental processes occurring on lithium coatings for fusion reactor walls.

In research exploring efficient uses of renewable electricity in chemical industries, Bruce studied heterogeneous catalytic reactions assisted by low-temperature, nonequilibrium plasma, and electrocatalysis to synthesize chemicals and fuels from carbon dioxide at milder operating conditions than required by traditional thermal catalysis alone. Advances in this research were enabled by using surface analysis methods and in-situ probes of the electrodes during operation. His experiments at Brookhaven National Laboratory provided the first orbital-resolved scanning tunneling microscope images of a molecule on a compound semiconductor.

His work on low-temperature plasma led to key innovations in the direct recycling of cathode materials used in lithium-ion batteries, which became the technological basis for a company that spun out of his and his colleague’s labs. Called Princeton NuEnergy, the company Bruce cofounded has since raised substantial funding from several leading venture capital and industry foundation partners, as well as from the Department of Energy. Princeton NuEnergy aims to reduce recycling cost, environmentally hazardous waste, energy use, and CO2 emissions, along with reducing U.S. dependence on foreign sources for lithium-ion battery materials and production.

In a career that has spanned more than four decades, Bruce has advised forty-six Ph.D. students, forty-five postdoctoral researchers, and 115 undergraduate students. He has coauthored over 360 peer-reviewed journal publications and twelve book chapters. He and his research group have presented over 1,000 technical talks. His research has garnered nearly 20,000 citations.

Apart from his research contributions, Bruce played a vital role in the academic community at Princeton. Within CBE, he served as the undergraduate departmental representative (now called the director of undergraduate studies), marshalled the department’s ABET accreditation, and served as the inaugural chair of CBE’s Diversity, Equity, Climate, and Inclusion Committee. His teaching of CBE’s Ethics and Technology course reflects his commitment to shaping the ethical considerations of future engineers, especially regarding the impacts of the technologies they will develop. The central theme of that course revolves around a single question: What is the engineer’s responsibility? 

Beyond academia, Bruce’s life has been enriched by various hobbies and sports. His interests in weight training, biking, and long-distance running, including participation in marathons, illustrate his dedication to physical fitness and well-being. Bruce’s storied involvement in the CBE graduate student softball team and his competitive spirit over more than a decade running long-distance Masters meets in New Jersey are testaments to the value he places on personal well-being and physical endurance.

Looking forward to retirement, Bruce plans to continue his engagement with Princeton NuEnergy, where he serves on the technology advisory committee. His retirement also includes travel plans to visit family in Colorado and Los Angeles, as well as points abroad for leisure with his wife, Emily A. Carter, who is the Princeton Plasma Physics Laboratory’s strategic advisor for sustainability science and associate laboratory director for applied materials and sustainability sciences, as well as the Gerhard R. Andlinger Professor in Energy and the Environment, professor of mechanical and aerospace engineering, the Andlinger Center for Energy and the Environment, and applied and computational mathematics. Bruce has said he looks forward to dedicating more time to training, exercising, and enjoying long trail runs.

Bruce's career is a remarkable blend of scientific excellence, educational leadership, and personal dedication. His retirement marks the end of a significant chapter in his professional life but also the beginning of a new phase where his contributions to science and his personal passions will continue to thrive. His legacy in the field of chemistry and surface science and his commitment to education remain enduring, influential, and inspiring for future generations of scientists and educators.

Written by members of the Department of Chemical and Biological Engineering faculty.