Abstract
AbstractThe growth of noble‐metal single crystals via the flame fusion method was developed in the 1980s. Since then, there have been no major advancements to the technique until the recent development of the controlled‐atmosphere flame fusion (CAFF) method to grow non‐noble Ni single crystals. Herein, we demonstrate the generality of this method with the first preparation of fcc Cu as well as the first hcp and bcc single crystals of Co and Fe, respectively. The high quality of the single crystals was verified using scanning electron microscopy and Laue X‐ray backscattering. Based on Wulff constructions, the equilibrium shapes of the single‐crystal particles were studied, confirming the symmetry of the fcc, hcp, and bcc single‐crystal lattices. The low cost of the CAFF method makes all kinds of high‐quality non‐noble single crystals independent of their lattice accessible for use in electrocatalysis, electrochemistry, surface science, and materials science.
Highlights
Non-noble transition metals are widely used in a variety of fields, such ascatalysis, fuel-cell development, electrode materials for battery systems, electronic devices, Dr J
This method is an improvement of the flame fusion method originally developed by Clavilier in the 1980s,[21] where a metal wire was melted in a hydrogen-oxygen flame
The resulting liquid metal bead is slowly cooled by lowering the flame, resulting in a bead-shaped single crystal, where various facets of low and high Miller-index surfaces are observed on the surface of the crystal.[21]
Summary
Non-noble transition metals are widely used in a variety of fields, such as (electro-)catalysis, fuel-cell development, electrode materials for battery systems, electronic devices,. While there has been considerable research involving polycrystalline Cu, Co, and Fe, little research has been conducted on monocrystalline materials of these three metals This is, in part, due to the high cost of commercially available Cu, Co, and Fe single crystals, as the methods required to grow these single crystals rely entirely on expensive ultrahigh vacuum (UHV) techniques. Wulff constructions (using DFTcalculated surface energies) were performed to evaluate the observed structures of the grown systems These results show the generality of the method, demonstrating that it can be used to grow crystals of other oxygen-sensitive metals in addition to the previously described growth of Ni.[15] the CAFF method can be stated as a fast, effective, and cheap way for the in-house growth of noble- and non-noble-metal single crystals, which further extends the scope of all singlecrystal-preparation techniques without challenging any other technique. The discussion of advantages, disadvantages, as well as differences of the various existing single-crystalpreparation methods is certainly beyond the scope of the present work but could be the topic of a future extended review
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