In situ synchrotron study of Au–Pd nanoporous alloy formation by single-source precursor thermolysis

Abstract

We have successfully prepared a face-centered cubic Au–Pd nanoporous structure (NPS) in a one-pot reaction under thermal decomposition of single-source precursor [Pd(NH3)4][AuCl4]2. The precursor employed contains both desired metals ‘mixed’ on the molecular level, thus providing its significant advantages for obtaining alloys. The observation using a high-resolution transmission electron microscope has shown that the nanostructure was composed of interconnected polycrystalline ligaments with an average diameter of 14 ± 3 nm. The measurements made by energy-dispersive x-ray analysis and powder x-ray diffraction (XRD) confirm that the nanostructure consists of Au0.67Pd0.33 alloy. In situ real-time synchrotron XRD was used to study the formation mechanism for Au–Pd alloy NPS. We provide the correlation of control parameters (such as temperature, rate of increase of temperature and gas atmosphere) with the microstructure and phase behavior of bimetallic products. Under reducing conditions (H2 atmosphere) the first step is the formation of alloy nanowires. Finally, bimetallic alloy 3D nanostructure is formed after the complete decomposition of the precursor (100 °C).