Browsing by Author "Weber, Moritz Lukas"

Now showing 1 - 2 of 2

Open Access
Atomic‐scale insights into nanoparticle exsolution at dislocations in dislocation‐engineered catalysts
(2025) Weber, Moritz Lukas; Kindelmann, Moritz; Jennings, Dylan; Hölschke, Jan; Dittmann, Regina; Mayer, Joachim; Rheinheimer, Wolfgang; Fang, Xufei; Gunkel, Felix
Achieving control over properties such as density and lateral distribution of catalytic nanoparticles under operation conditions is a major challenge for the development of active and durable catalysts, where nanoparticle coarsening is often the cause of performance degradation. While metal exsolution catalysts are regarded to be robust against this degradation mode, coarsening and increased concentrations of exsolved metal nanoparticles have been detected near extended defects. The present study examines the role of dislocations in metal exsolution reactions and explores the potential of dislocation‐engineering for the synthesis of dislocation‐associated nanoparticles. An atomic‐level correlation between bulk dislocations and surface nanoparticle locations is demonstrated through a novel approach for engineering epitaxial thin films with confined regions of increased dislocation densities in combination with in situ scanning transmission electron microscopy. While nanoparticle exsolution proceeds across the entire sample, two primary reasons for the frequent nucleation of dislocation‐associated nanoparticles are identified: the accumulation of exsolution‐active acceptors along dislocations and lattice distortions that are likely to lower the energy barrier for nanoparticle nucleation. This work establishes a proof of concept for using engineered dislocations in exsolution catalysts to synthesize nanoparticles with modified nanoparticle‐support properties relevant for the thermal stability and the lateral distribution of exsolved nanoparticles.
Open Access
Controlling grain boundary segregation to tune the conductivity of ceramic proton conductors
(2024) Kindelmann, Moritz; Povstugar, Ivan; Kuffer, Severin; Jennings, Dylan; Ebert, Julian N.; Weber, Moritz Lukas; Zahler, Pascal; Escolastico, Sonia; Almar, Laura; Serra, Jose M.; Kaghazchi, Payam; Bram, Martin; Rheinheimer, Wolfgang; Mayer, Joachim; Guillon, Olivier
Acceptor‐doped barium zirconates are of major interest as proton‐conducting ceramics for electrochemical applications at intermediate operating temperatures. However, the proton transport through polycrystalline microstructures is hindered by the presence of a positive space charge potential at grain boundaries. During high‐temperature sintering, the positive charge acts as a driving force for acceptor dopant segregation to the grain boundary. Acceptor segregation to grain boundaries has been observed in sintered ceramics, but the fundamental relationship between the segregation kinetics and the protonic conductivity is poorly understood. Here, a comprehensive study of the influence of acceptor dopant segregation on the electrochemical properties of grain boundaries in barium zirconate ceramics is presented. An out‐of‐equilibrium model material that displays no detectable Y segregation at its grain boundaries is explicitly designed. This model material serves as a starting point to measure the kinetics of segregation and the induced changes in grain boundary conductivity upon varying thermal histories. Furthermore, the electrochemical results from impedance spectroscopy to atomic resolution transmission electron microscopy, atom probe tomography, and DFT simulations are correlated. It is discovered that acceptor dopant segregation drastically increases the proton conductivity in both the model system and several other application‐relevant compositions.