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| Book/Dissertation / PhD Thesis | FZJ-2024-03410 |
2024
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-753-0
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Please use a persistent id in citations: doi:10.34734/FZJ-2024-03410
Abstract: The transition to a sustainable energy system relies on the availability of high-performing and costeffective 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-consistentdescription 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.
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