BCC-Cu nanoparticles: from a transient to a stable allotrope by tuning size and reaction conditions

• Published in: Physical chemistry chemical physics : PCCP 2022-10, Vol.24 (39), p.24429-24438
• Main Authors: Alfke, Jan L, Müller, Andreas, Clark, Adam H, Cervellino, Antonio, Plodinec, Milivoj, Comas-Vives, Aleix, Copéret, Christophe, Safonova, Olga V
• Format: Article
• Language: English
• Subjects: Allotropy; Body centered cubic lattice; Chemistry; Copper; Face centered cubic lattice; Low temperature; Nanoparticles; Precursors; Synchrotrons
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d2cp03593f

Metallic copper generally adopts an FCC structure. In this work, we detect highly unusual BCC-structured Cu nanoparticles as a transient intermediate during the H 2 reduction of a Cu I precursor, [Cu 4 O t Bu 4 ], grafted onto the surface of partially dehydroxylated silica. The Cu BCC structure, assigned by in situ Cu K-edge XANES and EXAFS, as well as in situ synchrotron PXRD, converts upon heating into the most commonly found FCC allotrope. DFT calculations show that the BCC-Cu phase is in fact predicted to be more stable for small particles, and that their stability increases at lower H 2 concentrations. Using this knowledge, we show that it is possible to synthesize BCC-structured Cu nanoparticles as a stable allotrope by reduction of the same grafted precursor either in 10% H 2 diluted in Ar or 100% H 2 at low temperature. We detected unusual BCC-structured Cu nanoparticles via in situ XAS and pXRD and prepared them in a stable form on silica. DFT modeling indicates stability of the BCC-Cu structure in an inert atmosphere for particles