Quick-XAFS as a tool for study of chemical processes
- Dr. Tatyana ASANOVA
- Dr. Tatyana ASANOVA (Institute of Inorganic Chemistry)
Investigations of chemical processes in Chemistry have gain new opportunities thanks to Synchrotron Radiation Facilities allowing researchers to control and manage synthesis of inorganic compounds and new materials as well understand chemical reactions in details. One of the techniques for preparing nanoparticles (mono-, bi-, n-metallic) is a thermal decomposition of inorganic compounds such as molecular, complex compounds in the presence of a support material and without it under different atmospheres.
The work presents results of in-situ Quick-XAFS and XRD study of thermal decomposition of the double complex salt [Pd(NH3)4][OsCl6] in an inert atmosphere. The study purposes two objects. The first one is to find out all intermediate products, some of them has sometimes a short lifetime and could not be synthesized or isolated as the product from the thermal chemical process. Meanwhile the intermediate has its ability to effect on a final product. The second object is to observe a formation of bimetallic nanoparticles or nanoalloys (the final product) in real time. The compounds containing two metals were shown to be used for preparing bimetallic alloys with composition different from that a binary phase diagram predicts for a bulk alloys.
Quick-XAFS and XRD experiments were performed at Rock beamline of Soleil Synchrotron (Paris, France) and ID11 beamline of ESRF (Grenoble, France) respectively. All the thermal decomposition intermediates were found. One of the results of the study is a demonstration of distinguish in the thermal decomposition of (NH4)2OsCl6 as the intermediate product in the complex compound compared to a pure ammonium hexachloroosmate(IV) under the same condition. The formation of the PdOs bimetallic nanoalloy includes the following steps. At first, the Pd metallic particles are appeared. Then the bimetallic particles are formed. Finally, a partial segregation of the PdOs nanoalloy happens. Quick-XAFS and common XAFS experiments with [Pd(NH3)4][OsCl6] are compared demonstrating noticeable limitation of the common XAFS. In particular, it concerns to beginning process of formation of the small metallic particles.
This work is financially supported by RFBR research project N 17-03-00693 A/