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TY  - THES
AU  - Tesch, Rebekka
TI  - Structure and properties of electrochemical interfaces from first principles simulations
VL  - 629
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Jülich
M1  - RWTH-2024-03189
SN  - 978-3-95806-753-0
T2  - Schriften des Forschungszentrums Jülich. Reihe Energie & Umwelt/ Energy & environment
SP  - xvi, 161 Seiten : Illustrationen
PY  - 2024
N1  - Dissertation, RWTH Aachen University, 2024
AB  - The transition to a sustainable energy system relies on the availability of high-performing and cost-effective energy storage and conversion devices, such as batteries, fuel cells and electrolysers. The performance of these devices is directly related to the properties of the employed electrocatalyst materials. In order to develop electrochemical devices that can respond to societal, economical and environmental needs, catalyst materials must be improved in terms of activity, long-term stability and production cost. This requires significant progress in the fundamental understanding of relevant electrochemical processes. The majority of electrochemical processes take place at the interface between a solid electrode and a liquid electrolyte. Atomic-scale modeling is a powerful tool that can yield important information on structural, electronic and electrostatic properties of the interface. However, self-consistently modeling the two parts of the interface as well as their non-linear coupling is very challenging. Existing computational methods are limited in terms of accuracy and/or efficiency. The aim of this thesis is to address some of the limitations of existing methods and provide accurate computational methodologies for a realistic description of the local reaction conditions at the electrochemical interface and of the electrocatalytic processes. We focus on two aspects: (1) the efficient and accurate computation of the electronic structure of materials with strongly correlated electrons, such as d- or f-electrons, and (2) the self-consistent description of phenomena at electrochemical interfaces, including the effects of electrolyte species and electrode potential. For these purposes, two methods have been studied in detail in this thesis: (1) the DFT+U approach for the description of strongly correlated electrons and (2) the recently developed effective screening medium reference interaction site method (ESM-RISM) for the description of electrochemical interfaces. The conducted research enabled us to establish an improved DFT+U approach for the computation of the electronic structure of electrode materials. In this methodology, we derive the Hubbard U parameter from an existing first principles-based linear response method. Additionally, we use Wannier projectors instead of standard atomic orbitals projectors for more accurate counting of orbital occupations. The resulting scheme provides an improved electronic structure description of various d- and f-materials and allows, for example, for enhanced studies of catalytically active sites in oxide electrocatalysts. These results indicate that a correct electronic structure description is an important precondition for an accurate computational modeling of electrochemical interfaces. Regarding the electrochemical interface, we extensively tested, validated and applied the ESM-RISM for metal/electrolyte interfaces. Our research showed that the ESM-RISM is a powerful method for the computation of electrochemical interfaces, when applied with care regarding the parameterization of interactions and the description of the near-surface electrolyte structure. It is capable of delivering accurate information on various interface properties like the double layer structure, electrostatic interfacial potentials and surface charging relations. In particular, we were able to reproduce the measured non-monotonic charging relation of the partially oxidized Pt(111)/electrolyte interface. Finally, we combined both computational approaches to study NiOOH materials as catalysts for the electrochemical oxygen evolution reaction (OER). This investigation was possible only with the non-standard DFT+U scheme, since the standard DFT+U approach incorrectly predicts a metallic state for this semiconducting material. In this respect, we discuss problems of grand canonical approaches for simulating electrified semiconductor/electrolyte interfaces. Accounting for the local reaction environment, we computed thermodynamic overpotentials for the OER, surface charging relations and properties of active sites depending on the potential-dependent degree of surface deprotonation. These results pave the way for more realistic simulations of electrochemical systems. The outcome of this thesis enables improved and more accurate treatments of atomic-scale processes at electrochemical interfaces at reasonable computational cost. Providing a sound methodological basis, the investigated methods allow going beyond previous computational studies in terms of the description of electrochemical conditions. These methodologies, although still far from being able to self-consistently account for all relevant electrochemical phenomena, should lead to improved understanding of electrochemical materials. In this way, they help develop improved catalyst materials for energy devices that are required for implementing the energy transition.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
UR  - https://publications.rwth-aachen.de/record/981735
ER  -