David Heldebrant
Division Director
Dr. David J. Heldebrant is the current director of the Physical Sciences Division at Pacific Northwest National Laboratory (PNNL). He previously served as a Team Lead of the Separations Materials team under the Advanced Energy Systems Group in the Energy Processes and Materials Division and sub-sector manager for Fossil Energy Carbon Management. He is a Research Associate Professor of Chemical Engineering and Bioengineering at Washington State University.
His work spans both fundamental and applied sciences, where he currently leads programs for the DOE offices of Fossil Energy and Carbon Management, Industrial Technologies Office, ARPA-E, and the Office of Science. Heldebrant has published 98 papers, co-authored 2 book chapters and has been awarded 23 US patents.
Aaron Appel
Group Leader - Catalysis Science
Aaron Appel is an inorganic chemist with broad interests in chemical reactivity, electrochemistry, and catalysis. His fundamental science research has two primary areas of emphasis: thermodynamic studies of discreet bond forming and bond breaking events, and the design and testing of complexes and catalysts based on the resulting thermodynamic data. This approach has been applied to a variety of transformations, including those of H2 and CO2.
Appel's primary areas of expertise are thermochemical measurements, electrochemistry, catalyst design, synthetic chemistry, and small molecule spectroscopy. He also has a background in CO2 capture research, particularly in developing new methods with higher energy efficiency, such as electrochemically switchable CO2 capture.
Scott Smith
Group Leader - Chemical Physics and Analysis
Scott Smith’s research interests are in the kinetics and dynamics of gas/surface interactions and of supercooled liquids and amorphous solids. His work combines detailed experimental measurements with kinetic models to accurately simulate adsorption, desorption, and reactions at the gas/surface interface. Dr. Smith’s research also involves the characterization of the kinetic behavior of crystalline ice and amorphous solid water, and understanding phenomena occurring in deeply supercooled liquids; he is developing kinetic models to describe the desorption and diffusive behavior of deeply supercooled liquids near their glass transition temperature. Dr. Smith holds a PhD in physical chemistry from the University of Utah (1988).
Carolyn Pearce
Group Leader - Geochemistry
Carolyn Pearce works on the characterization of minerals relevant to radioactive waste storage and processing in order to determine reaction mechanisms and kinetics that affect radionuclide stability in waste forms and subsurface environments. In 2021, she was named Director of the Ion Dynamics in Radioactive Environments and Materials (IDREAM) Energy Frontier Research Center. IDREAM researchers conduct fundamental science to support innovations in retrieving and processing highly radioactive waste.
Pearce joined the Center for the Remediation of Complex Sites (RemPlex) as Deputy Director in March 2026. In 2022, she was appointed an honorary professor with the Department of Earth and Environmental Sciences and the Dalton Nuclear Institute at the University of Manchester, United Kingdom.
Ajay Karakoti
Group Leader - Materials
Ajay Karakoti's research is focused on discovering the principles of the synthesis of materials and their integration into substrates of different size, shape, porosity, and textures. He also works on developing a fundamental understanding of the effect of the local environment on the functionalization, activity, and stability of materials. He is interested in discovering the role of autonomous science in accelerating and controlling the end points of materials synthesis. His research has direct application in areas related to redox cycling of materials including heterogenous catalysis, microelectronics, and energy technologies.
Beth Randle
Division Administrator
Beth Randle is a seasoned administrative professional with over 13 years in the field. Beth supports David Heldebrant and the Physical Sciences Division. Before joining PNNL in 2015, she worked as an account coordinator for a brand and digital agency firm, where she organized specialty business conferences. Previously, she owned and operated her own retail business. Beth holds a BA in Arts, Entertainment and Media Management from Columbia College Chicago.
