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%0 Thesis
%A Berger, Maike
%T Eisen-Nickel-basierte Doppelschichthydroxide als Elektrokatalysatoren für die alkalische Wasserelektrolyse
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2025-08904
%P 1 Online-Ressource : Illustrationen
%D 2025
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, RWTH Aachen University, 2025
%X Green hydrogen represents a promising energy carrier for the large-scale storage of renewable energy and is therefore the focus of current research. The use of highly active, precious metal-free catalysts is an important contribution to increasing the competitiveness of green hydrogen. This research focuses on the study and optimization of NiFe-based layered double hydroxides as electrocatalysts in the oxygen evolution reaction, which show high potential due to their cost efficiency, high availability, and promising catalytic performance. To improve catalytic performance, various approaches were chosen to optimize the material, and promising systems were kinetically studied. Initially, alongside iron and nickel, other 3d-transition metals were incorporated. The resulting increase in activity was attributed to the enhanced conductivity due to a changed electronic structure of the LDH layers. Another property of the material, the ability to incorporate various anions into the interlayers, was utilized to positively influence performance. Anions were able to increase catalytic activity by affecting the interlayer distance and charge transfer resistance. Simple anions were first chosen for an initial investigation, and a detailed kinetic analysis was carried out using electrochemical steady-state techniques. Based on the results, the mechanism of OER catalysis on NiFe LDH was identified, as well as the adsorption conditions of the intermediates, and rate-determining steps were calculated. These kinetic findings were further confirmed in another series of anion exchanges based on inorganic and organic borates. While organic borates, due to their aromaticity and the accompanying greater delocalization of negative charge, had an activity-reducing effect on OER performance, the incorporation of B(OH)4−, due to its strong Lewis basicity, resulted in increased activity. As another class of anions, sulfur-based anions were chosen and successfully incorporated into the interlayer. The materials exhibited significant agglomeration regardless of the electrode material. A thorough activity analysis was performed, and dependencies of the activity on interlayer distance, pKs value of the conjugate acid, and redox reactivity were examined. Finally, a new manufacturing method for this application, co-precipitation in an inverse microemulsion, was tested, aimed at producing nanoscale NiFe LDHs with a narrow particle size distribution. It was found that smaller crystallites led to improved OER activity. Smaller crystallites potentially lead to more grain boundaries, and thus a modified electronic surface structure, which can be beneficial for OER performance.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2025-08904
%U https://publications.rwth-aachen.de/record/1020331