Fabricating materials into nanoparticle is proved an effective strategy to maximize their performance for the application, and one of the most important nanoparticle applications in catalysis stand out among other successful practices. Catalysts are often designed in the form of oxide-supported metal particles, due to that nanoparticles could offer a larger surface to support the metal atoms as active sites.[1] In addition, the catalytic performance is size and shape-dependent, and position and arrangement of their metal clusters embedded in the matrix could also remarkably alter their catalytic capacity. Therefore, a technique capable of linking their property and microstructure is essential for the catalyst assessment and development.
Atom probe tomography (APT) could reveal chemical information of the samples with part per million detection sensitivity, and therefore providing a visualized atomic-scale tomography for the sample assessment. However, APT requires a solid needle-shaped specimen for experiment and it is quite challenging to prepare APT needle specimen from nanoparticle samples, which limits their application to the catalyst. So far, there is no report regarding an all-round method for all kinds of particles, the reported methods are specialized on nanoparticles with specific properties such as particular dimension,[2] easy evaporating.[3] In this work, we propose an effective method to prepare APT specimen for nanoparticles within the dimension of ~ 100 to 200 nm, by combining electrophoresis and focus ion beam annular milling. The particle used in this study was Ni@SiO2 catalyst. Moreover, an additional iridium shell (~15 nm) was intentionally deposited onto the as-prepared tips in order to strengthen the specimen. This work provides an efficient method to prepare APT specimen from nanoparticles with intermediate size, advancing APT application into catalysis.
References
[1] Science, 248(4960), 1186-1188, 1990.
[2] ACS Catal., 4(2), 695-702, 2014.
[3] Microsc. Microanal., 25(2), 438-446, 2019.