Local atomic and electronic structure of Pt-Os nanoplates and nanofibers derived from the single-source precursor (NH4)2[Pt0.5Os0.5Cl6].

Nowadays, Pt-Os binary systems are mainly considered as catalysts and electrocatalysts, but the role of Os in these processes is still poorly understood. The electronic structure of Pt-Os nanosystems remains a few studied as well. Using bimetallic (NH₄)₂[Pt_0.5Os_0.5Cl₆] as a single-source precursor for preparing Pt-Os nanoalloy through the thermal decomposition in hydrogen and inert atmospheres, the relation of morphology, atomic ordering, and electronic structure of Pt-Os nanoalloy was examined by in situ Quick XAFS, XPS, PXRD, SEM, and HRTEM techniques. Being the only variable parameter, the decomposition atmosphere was found to govern the morphology of the Pt-Os nanoalloy and change the atomic ordering (alloying extent), which involves a change in the electronic structure. In a hydrogen atmosphere, the nanofibers (NFs) (ø ~ 5–6 nm) with the atomic ordering Os_core&Pt-rich_shell were observed to form; in a nitrogen atmosphere, thin nanoplates (NPLs) (~ 12 nm) with the atomic architecture Os-rich_core&Pt-rich_shell were found out. The depletion in the Os 5d_5/2 and Pt 5d_5/2,3/2 states was revealed for Pt-Os nanoalloys. This unusual result disagrees with the known d-band theory and indicates that there is a gain of non-d conduction electron counts at one or both sites. Mixed conductivity may exist in such Pt-Os nanoalloy that may be responsible for a manifestation of new physical properties of this binary system. [ABSTRACT FROM AUTHOR]