Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Karis R. Barnett - University of Maryland, Baltimore County
Co-Author(s): Venkateshkumar Prabhakaran, Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352; Grant E. Johnson, Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352
Molecular-level understanding of charge transfer processes in redox-active species at electrochemical interfaces enables rational design of high-performance energy storage technologies. A combination of scanning electrochemical cell microscopy (SECCM) and spectroscopy reveals spatially localized reactions occurring during redox processes. In this work, we studied how chemical transformations occurring in single (e.g., Ferrocenemethanol, FcMeOH) and two-electron redox transfer species (e.g., 9,10-anthraquinone-2,6-disulfonic acid disodium salt, AQ) affect their electrochemical performance. Specifically, a microscale SECCM was used to measure the diffusion of redox ions (FcMeOH and AQ) in 0.1 mM hydrochloric acid on indium tin oxide (ITO) electrodes. The diffusion coefficients calculated from the data indicate that the formation of neutral species impedes migration of ions during reduction of FcMeOH. In contrast, AQ showed the same diffusion coefficient for both processes, reflecting no formation of neutral species. High-resolution electrospray ionization-mass spectrometry was used to identify the charged species of FcMeOH and AQ present in electrolytes. A peak shift observed using ultraviolet-visible spectroscopy confirmed the formation of neutral vs. charged species in FcMeOH and only charged species in AQ on electrodeposited ITO electrodes. We hypothesize that the formation of neutral species may be avoided in energy storage devices to promote facile ionic diffusion during charge/discharge processes and higher overall device performance. Future work will explore the possibilities of in situ spectroscopic characterization of redox electrochemistry on well-defined electrodes.
Funder Acknowledgement(s): Funder Acknowledgement: This work was supported by the U.S. Department of Energy, Office of Science - Basic Energy Sciences, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program. Special acknowledgements to SULI program staff Nicole Castilleja-Bentley and Alexa Williams.
Faculty Advisor: Venkateshkumar Prabhakaran; Grant E. Johnson, firstname.lastname@example.org
Role: In terms of experimental work, I conducted the tests (including preparing species and running instrumentation) needed for data collection and analyzed said data. My advisor provided additional assistance with analysis of ultraviolet-visible spectroscopy data plotting and analysis. In terms of project deliverables, I composed a research paper, poster, and oral presentation with the guidance of my advisors and division team.