Publication date: 21st July 2025
Metal exsolution reactions yield a high density of finely dispersed nanoparticles at the surface of functional oxides, enabling the synthesis of efficient electrocatalysts. The exsolution behaviour of reducible metals from host oxides and the nanoparticle self-assembly is closely linked to the oxides’ defect structure. Consequently, defect engineering has emerged as a strategy to control the properties of exsolution catalysts, with a primary focus on modifying point defect concentrations in exsolution-active host oxides.
We explore dislocation engineering to tune nucleation sites for metal nanoparticles formed under the reducing reaction conditions. For this purpose, we developed a novel approach to induce laterally confined regions of increased dislocation densities into oxide thin films. This method is based on mechanical deformation of single-crystal substrates followed by the deposition of epitaxial thin films using pulsed laser deposition. Based on this methodology, exsolution-active Ni-doped strontium titanate model systems with defined areas of pre-engineered dislocations are synthesized, which enable the investigation of the role of dislocations in metal exsolution reactions on the atomic scale.
We use environmental scanning transmission electron microscopy with simultaneous bulk-sensitive and surface-sensitive image detection to study the formation of dislocation-associated metal nanoparticles. The in-situ analysis reveals a clear correlation between the presence of pre-engineered bulk dislocations in the exsolution-active oxide and the formation of surface nanoparticles. Two major reasons for the dislocation-associated nanoparticle formation are identified. First, the accumulation of exsolution-active acceptors along dislocations, driven by electrostatic interactions and lattice strain. Second, lattice distortions that are expected to decrease the energy barrier for nanoparticle nucleation during metal exsolution reactions.
Beam-time access at Ernst Ruska-Centre (ER-C) for Microscopy and Spectroscopy with Electrons at the Forschungszentrum Jülich was provided in part via the DFG Core Facility Project ERC D-093. This work was supported in part by Japan Science and Technology Agency (JST) as part of Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE), Grant Number JPMJAP2307.
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