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SUMMARY:Structural study of Pt-complexes in aqueous solution by EXAFS
DTSTART;VALUE=DATE-TIME:20200713T141500Z
DTEND;VALUE=DATE-TIME:20200713T141600Z
DTSTAMP;VALUE=DATE-TIME:20260419T151004Z
UID:indico-contribution-1865@indico.inp.nsk.su
DESCRIPTION:Speakers: Vladimir Kriventsov ()\nThis work is devoted to the 
 study of the process of hydrolysis of chloride Pt(II) complexes and Pt(IV)
  nitrate complexes existing in aqueous solutions of different nature by EX
 AFS spectroscopy.\nThe deposited platinum catalysts are inevitable in vari
 ous industrial oxidation and reduction processes due to their unique prope
 rties\,. The variety of catalytic properties is determined by the possibil
 ity of varying the dispersion and lability of the active component. It is 
 quite obvious that the development of methods for fine control of Pt dispe
 rsion is necessary to study the fundamental relationships between the size
 \, state of the active component nanoparticles\, their detailed electronic
  structure\, and the actual properties of a catalyst in a chemical reactio
 n. As a rule\, various precursor solutions based on Pt(IV) and Pt(II) salt
 s are used for the synthesis of platinum catalysts\; after precipitation t
 o a carrier the system undergoes various heat treatments. The main factor 
 affecting the dispersion of Pt forms existing in salt solutions is the ong
 oing hydrolysis process. To implement the research goals\, ~0.01-0.05 M aq
 ueous solutions of K2 PtCl4 and nitrate solutions of Pt (IV) with differen
 t ligand environments were prepared and  EXAFS spectra (Pt-L3 edge) of stu
 died samples were recorded at SSTRC\, Novosibirsk. The composition and str
 uctures of the hydrolysis products being polynuclear platinum (II) hydroxo
 complexes (PHC-Pt) were studied. It was found that during the hydrolysis r
 eaction of [PtCl4]2-complexes\, oligomeric chains containing Pt-O-Pt fragm
 ents are formed\, in which neighboring Pt atoms are connected by a single 
 O–bridge atom. Aging of solutions containing PHC-Pt for a long time\, by
  formation of 3D-oxide structures. does not take place\, in contrast to so
 lutions of PHC-Pd (II) and PHC-Pt (IV). Increase in size of PHC-Pt particl
 es is shown to take place while the process of oligomerization of Pt(II) m
 ononuclear complexes proceeds. It was shown that during hydrolysis of Pt(I
 V) nitrate solutions\, Pt(IV) polynuclear hydroxocomplexes were formed. It
  was established that the nearest environment of Pt in these solution is a
 lways octahedral\, with the distortion caused by replacing the O part with
  the N part. However\, formation and stabilization of various agglomerated
  Pt-containing forms of different nuclea are possible. It was found out th
 at the nuclearity of various forms and their resistance to hydrolysis depe
 nd on the preliminary history of the sample and the nature of O\, N-ligand
 s in the platinum coordination sphere platinum in the solutions. The Pt-O\
 , N\, and Pt-Pt distances and corresponding coordination numbers are deter
 mined. Variants of possible structural models are considered. Additionally
 \, all prepared samples of solutions were examined by NMR\, TEM methods. D
 ata from all these methods agree with each other.\nThe work was carried ou
 t in the framework of the RFBR projects no. 19-05-50046\, 18-03-01251. The
  work was done at the shared research center SSTRC on the basis of the Nov
 osibirsk FEL/VEPP-4-VEPP-2000 complex at BINP SB RAS\, using equipment sup
 ported by project RFMEFI62119X0022.\n\nhttps://indico.inp.nsk.su/event/24/
 contributions/1865/
LOCATION:
URL:https://indico.inp.nsk.su/event/24/contributions/1865/
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