The Ce 3+ /Ce 4+ redox potential changes with the electrolyte, which could be due to unequal anion complexation free energies between Ce 3+ and Ce 4+ or a change in the solvent electrostatic screening. Ce complexation with anions and solvent screening also affect the solubility of Ce and charge transfer kinetics for electrochemical reactions involving waste remediation and energy storage. We report the structures and free energies of cerium complexes in seven acidic electrolytes based on Extended X-ray Absorption Fine Structure, UV−vis, and Density Functional Theory calculations. Ce 3+ coordinates with nine water molecules as [Ce(H 2 O) 9 ] 3+ in all studied electrolytes. However, Ce 4+ complexes with anions in all electrolytes except HClO 4 . Thus, our results suggest that Ce 4+ −anion complexation leads to the large shifts in standard redox potential. Long range screening effects are smaller than the anion complexation energies but could be responsible for changes in the Ce solubility with acid.

A large portion of life cycle transportation impacts occur during vehicle operation, and key improvement strategies include increasing powertrain efficiency, vehicle electrification, and lightweighting vehicles by reducing their mass. The potential energy benefits of vehicle lightweighting are large, given that 29.5 EJ was used in all modes of U.S. transportation in 2016, and roughly half of the energy spent in wheeled transportation and the majority of energy spent in aircraft is used to move vehicle mass. We collect and review previous work on lightweighting, identify key parameters affecting vehicle environmental performance (e.g., vehicle mode, fuel type, material type, and recyclability), and propose a set of 10 principles, with examples, to guide environmental improvement of vehicle systems through lightweighting. These principles, based on a life cycle perspective and taken as a set, allow a wide range of stakeholders (designers, policy-makers, and vehicle manufacturers and their material and component suppliers) to evaluate the trade-offs inherent in these complex systems. This set of principles can be used to evaluate trade-offs between impact categories and to help avoid shifting of burdens to other life cycle phases in the process of improving use-phase environmental performance.

The Ce3+/Ce4+ redox couple has a charge transfer (CT) with extreme asymmetry and a large shift in redox potential depending on electrolyte composition. The redox potential shift and CT behavior are difficult to understand because neither the cerium structures nor the CT mechanism are well understood, limiting efforts to improve the Ce3+/Ce4+ redox kinetics in applications such as energy storage. Herein, we identify the Ce3+ and Ce4+ structures and CT mechanism in sulfuric acid via extended X-ray absorption fine structure spectroscopy (EXAFS), kinetic measurements, and density functional theory (DFT) calculations. We show EXAFS evidence that confirms that Ce3+ is coordinated by nine water molecules and suggests that Ce4+ is complexed by water and three bisulfates in sulfuric acid. Despite the change in complexation within the first coordination shell between Ce3+ and Ce4+, we show that the kinetics are independent of the electrode, suggesting outer-sphere electron-transfer behavior. We identify a two-step mechanism where Ce4+ exchanges the bisulfate anions with water in a chemical step followed by a rate-determining electron transfer step that follows Marcus theory (MT). This mechanism is consistent with all experimentally observed structural and kinetic data. The asymmetry of the Ce3+/Ce4+ CT and the observed shift in the redox potential with acid is explained by the addition of the chemical step in the CT mechanism. The fitted parameters from this rate law qualitatively agree with DFT-predicted free energies and the reorganization energy. The combination of a two-step mechanism with MT should be considered for other metal ion CT reactions whose kinetics have not been appropriately described.

for sharing their expertise related to life cycle assessment, lightweighting, and the transportation system in general throughout this project. Their constant guidance and weekly meetings ensured that this research project was on track and ultimately successful. Additionally, their sound counsel on matters as far ranging as PhD programs and travel in Ireland were very much appreciated. It has been an honor to work with all three of these experts. I would also like to thank my fellow graduate student Marwan Charara for his work on the shipping container model and paper we published related to this study. Without his involvement, the study would not have been nearly as comprehensive. This research was conducted through Lightweight Innovations for Tomorrow (LIFT), a collaboration between universities and private industries to promote the development of lightweight materials manufacturing technologies. This work was directly supported by ALMMII (American Lightweight Materials Manufacturing Innovation Institute), which is sponsored by the U.S. Navy's Office of Naval Research (Cooperative Agreement Number N00014-14-2-0002 issued by the U.S. Department of Defense). In addition, I wish to acknowledge the following for their helpful contributions: Alan Taub for his technical and practical comments, Matt Collette for sharing his detailed knowledge of the shipping industry, Adithya Dahagama for his descriptions of marine ports, Krutarth Jhaveri for his weekly feedback, Soren Johannsen for his container expertise, and Randy Stiefel, Paul Weidenfeller, Brian Slack, and Helaine Hunscher for their support throughout the course of the work. I would also like to thank my parents for their support and advice throughout my graduate school experience. iii Preface This thesis is an exploratory study conducted through Lightweight Innovations for Tomorrow (LIFT) to investigate the energy consumed and greenhouse gases emitted during the multimodal life cycle of a shipping container as well as the potential reductions in environmental burdens for six container lightweighting scenarios. The burdens and savings are reported first for a single shipping container, and then are scaled up to indicate the savings possible if all shipping containers were lightweighted first in the United States and then globally. Additionally, a case study is conducted to examine the environmental burdens associated with several routes possible for the transportation of shipping containers from Shanghai to Detroit, Michigan. This thesis highlights the tradeoff between fuel savings incurred through lightweighting and potential increased production burdens associated with some of the lightweighting strategies. Furthermore, it indicates the influential nature of modal distribution and route selection on life cycle results and demonstrates a specific use of multimodal modeling that could be replicated and applied to other transportation systems. The work presented in this thesis has been recently published in the journal Transportation

Despite the interest in renewable energy as a substitute for fossil fuels, renewables make up less than 20%1 of total electrical energy in the United States in part because their intermittency prevents them from being a dominant fraction without storage.2 The redox flow battery (RFB) is a promising energy storage technology because of its high-power density and long lifetime,2 which can be used to address intermittency by decoupling customer demand and renewable electricity generation. Currently, however, RFBs incur substantial energy losses during operation at high current densities and are therefore too costly for market deployment. A promising chemistry for the positive electrode of a RFB which would improve efficiency by increasing the total voltage is the cerium redox couple, which has a potential up to 0.74 V greater than the positive vanadium electrode.3,4 The Ce3+/Ce4+ electron transfer redox potential changes depending on the electrolyte,3 which we hypothesize is due to the anion complexation thermodynamics. It is not currently clear whether only one or both of the Ce ions are complexed by anions in solution. Knowledge of the structures and free energies of cerium ions in acidic electrolytes would enable control over the Ce3+/Ce4+ redox potential for RFB applications. Additionally, understanding whether the Ce3+/Ce4+ redox reaction involves a change in the inner sphere is important for discerning the charge transfer mechanism and kinetics. In addition to a lack of information on the structure of Ce3+ and Ce4+ anions in acids, previous work in zinc-cerium5,6 and hydrogen-cerium7 batteries show that the cerium electrode kinetics are a limiting factor on battery performance. Our preliminary kinetic studies of the redox couple in sulfuric acid indicate that the kinetics are influenced more by the electrolyte than by the electrode material, which is consistent with an outer-sphere electron transfer mechanism. If the Ce3+/Ce4+ electron transfer does proceed via an apparent outer-sphere mechanism, the reorganization energy,8 which is dependent on the electrolyte, will control the rate of reaction. To determine whether the reaction follows an outer-sphere mechanism, we must isolate the behavior of the cerium ions at the electrode interface. In this study, we therefore explore the structure of the electrode-electrolyte interface as well as study the structure of cerium anion complexes. To probe the electrode-electrolyte interface, we use in-situ Extended X-ray Absorption Fine Structure (EXAFS) of the platinum (Pt) L3-edge of a Pt electrode during Ce3+ oxidation in two of the most relevant electrolytes for battery applications, H2SO4 and CH3SO3H. At the high positive potentials applied, the Pt is oxidized, and therefore the relevant electrode is a Pt-oxide. To study the ionic structure in different aqueous acidic electrolytes (i.e., HCl, H2SO4, H3NSO3, CH3SO3H, HNO3, CF3SO3H, and HClO4) and extract free energies of Ce3+ and Ce4+ complexes, we use experimental UV-Vis spectroscopy and EXAFS, and Density Functional Theory (DFT) calculations. Based on the combination of spectroscopy, DFT calculations, and the direction of the redox potential shift from non-complexing media, we hypothesize that Ce4+ is complexed by anions in electrolyte, while Ce3+ is hydrated by water. We find from the UV-Vis spectra that the dominant Ce3+ structure is the same in all acids studied, and that the dominant Ce4+ complex changes with electrolyte. EXAFS of Ce3+ allows us to determine a coordination number of nine water molecules. Our DFT calculations enable us to extract bond lengths of the first coordination shell of the cerium ions. The DFT-predicted free energies of Ce4+ anion complexation agree with free energies we calculated from redox potentials reported in literature, supporting our hypothesis that the shift in redox potential can be attributed to the anion complexation of Ce4+. Additionally, this agreement shows that we can predict standard redox potentials for cerium in simple aqueous electrolytes. Ultimately, these characterization findings clarify the fundamental interactions of cerium ions with their electrolyte environment and a relevant electrode as well as the Ce3+/Ce4+ thermodynamics and will guide kinetics studies of the Ce3+/Ce4+ redox couple for use in redox flow battery applications. U.S. EIA, Electric Power Annual (2019). Weber, A. et al. J. Appl. Electrochem. 41, 1137–1164 (2011). Piro, N. et al. Coord. Chem. Rev. 260, 21–36 (2014). Smith, G. & Getz, C. Ind. Eng. Chem. Res. 10, 191–195 (1938). Walsh, F. et al. Chempluschem 80, 288–311 (2015). Nikiforidis, G. et al. Electrochim. Acta 140, 139–144 (2014). Tucker, M. et al. J. Power Sources 327, 591–598 (2016). Bard, A. & Faulkner, L. (John Wiley & Sons, Inc., 2001).