[Ifeffit] Ifeffit Digest, Vol 113, Issue 17

[Branko Zugic]

Hi Anatoly,

I've only tried approximating using the short bond at 2 A up until now.
Below are the spectra that I'm trying to interpret. These are merged QEXAFS
data taken at increasing temperature under WGS conditions. Perhaps I
haven't processed them well enough? There certainly seem to be changes
taking place during the course of reaction, which I'm trying to interpret.

Given that the material starts out very well dispersed (I've observed many
sub-nm Pt clusters via ac-STEM) and grow to 1-2 nm particles during
reaction, I would expect to observe corresponding structural changes during
reaction. I also observe significant changes in the EXAFS spectra when
alternating between WGS gas and He - hence my thought to including some
kind of Pt-C and Pt-O paths, similar to those used in the Ir4(CO)12 work.

Thanks for any help!


Branko



On Sat, Jul 28, 2012 at 1:00 PM,
<ifeffit-request at millenia.cars.aps.anl.gov>wrote:

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>    1. Re: Modeling Pt/C Catalyst Under WGS Conditions
>       (Anatoly I Frenkel)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 28 Jul 2012 01:02:23 +0000
> From: Anatoly I Frenkel <afrenke2 at yu.edu>
> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Modeling Pt/C Catalyst Under WGS Conditions
> Message-ID: <98fc47e6-bd47-4c56-8fb2-3385fa7dbbbe at blur>
> Content-Type: text/plain; charset="utf-8"
>
> Maybe your system is more complex? Have you included a long Pt-O bond at
> around 2.5 A or just a short one at around 2A? Hard to help without seeing
> what the problem is.
>
> Anatoly
>
>
>
> Sent from my mobile phone, please forgive typos
>
>
> -----Original message-----
> From: Branko Zugic <Branko.Zugic at tufts.edu>
> To: "ifeffit at millenia.cars.aps.anl.gov" <ifeffit at millenia.cars.aps.anl.gov
> >
> Sent: Fri, Jul 27, 2012 15:28:37 GMT+00:00
> Subject: [Ifeffit] Modeling Pt/C Catalyst Under WGS Conditions
>
> Hello,
>
> I am trying to interpret some in-situ Quick-EXAFS and EXAFS data that I
> took under water-gas shift conditions (CO + H2O diluted in He) on some Pt/C
> catalysts. I'm finding that the Pt-Pt and Pt-O fits using foil data, Pt-O
> standards, and quick 1st shell approximations for Pt-O aren't that great.
> After looking through the literature I came across some papers (i.e.
> http://pubs.acs.org/doi/abs/10.1021/jp983283e) that use the Ir-O and Ir-C
> interactions from Ir4(CO)12 to approximate Pt-O and Pt-C interactions. I
> then found some crystallographic tables for Ir4(CO)12 (below), but it's
> unclear to me whether I can use this to create an atoms inp file (and
> whether the data is for the structure I'm looking for or the referenced
> Ir(CO)3). So far I've had no luck.
>
> Is this a reasonable approach to this problem? Is the information I have
> enough to do this? Any suggestions as to where I may be able to find the
> crystallographic data I am looking for?
>
>
> Branko Zugic
>
>
> --
> PhD Candidate
> Tufts University, Chemical and Biological Engineering
> 4 Colby Street, Room 226
> Medford, MA 02155
> Ph: (O) 617 627 2267 (H) 508 414 8555
> Email: Branko.Zugic at tufts.edu<mailto:Branko.Zugic at tufts.edu>,
> brankozugic at gmail.com<mailto:brankozugic at gmail.com><mailto:
> brankozugic at gmail.com>
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> End of Ifeffit Digest, Vol 113, Issue 17
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>



-- 
PhD Candidate
Tufts University, Chemical and Biological Engineering
4 Colby Street, Room 226
Medford, MA 02155
Ph: (O) 617 627 4338 (C) 508 414 8555
Email: Branko.Zugic at tufts.edu, brankozugic at gmail.com
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