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Liquid phase tabletop XUV spectroscopy for the study of transition metal catalysts Liquid phase tabletop XUV spectroscopy for the study of transition metal catalysts

Liquid phase tabletop XUV spectroscopy for the study of transition metal catalysts - PowerPoint Presentation

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Liquid phase tabletop XUV spectroscopy for the study of transition metal catalysts - PPT Presentation

Kristin Benke ISMS 2017 Ultrafast tabletop XUV spectroscopy 2 3p 6 3d n 3p 5 3d n 1   High harmonic generation HHG Gasfilled cell NIR laser Popmintchev T et al Proc Natl Acad Sci ID: 637264

spectroscopy xuv gas window xuv spectroscopy window gas 100 chem liquid sample state tabletop 2016 µm deformation edge phys

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Slide1

Liquid phase tabletop XUV spectroscopy for the study of transition metal catalysts

Kristin BenkeISMS 2017Slide2

Ultrafast tabletop XUV spectroscopy

2

3p

6

3d

n 3p53dn+1

 

High harmonic generation (HHG)

Gas-filled cell

NIR laser

Popmintchev

, T., et. al. Proc. Natl. Acad. Sci. 2009, 106, 10516-10521.Slide3

XUV spectroscopy gives electronic structure of metal-centered complexes.

3

Zhang, K.,

et. al. J

. Phys. Chem. Lett.

  2016, 7, 3383-3387.HHG output

Ligand field differentiationSlide4

Ultrafast XUV spectroscopy is well suited to study metal-centered catalysts.

Raugei, S. et. al. ACS Catal

.

,

2015

, 5, 5436-5452.Ni+

Ni0

Ni

2+Ni2+Ni+

Ni2+

Ni0

Ni+

Ni0DuBois’ catalyst

4

Techniques used to study catalysis

EPR

tUV

/Vis

tIR

Synchrotron based

tXAS

and

tXESSlide5

Studying a homogenous catalyst requires liquid phase compatibility.

5

Thin film for XUV spectroscopy

http://cxro.lbl.gov

/

Predicted transmission of XUV light by common solventsSlide6

Liquid phase tabletop XUV spectroscopy

requires a specialized liquid flow cell.

6

1 cm

X-ray transmissive silicon nitride windows

Compatible with high vacuum

Continual sample renewal prevents sample damageSlide7

 

Transmission of XUV flux is hindered by behavior of the window under vacuum.

7

Window deformation

spacer length

Maximum deflection at center (

) can be controlled by

membrane

thickness (

)

window dimensions (

)

pressure across membrane (

)

 

P

vacuum

 Slide8

Adjacent fields have implemented various methods to mitigate window deformation.

8

Dukes

, M.

J.

Microsc. Microanal. 2013, 19 (

Suppl 2), 406–407.Environmental TEMSlide9

Adjacent fields have implemented various methods to mitigate window deformation.

9

Nagasaka

, M.

J. Electron

Spectros. Relat. Phenomena 2010, 177 (2-3), 130–134.

Soft x-ray XASSlide10

Window deformation can be alleviated by locally increased pressure.

10

Implementation for tabletop XUV spectroscopy requires minimization of losses in flux

gas in

gas outSlide11

Adjusting the gas pressure allows for a tunable pathlength.

11

Transmission at

corresponding

pathlengths

Images of window at

different

pathlengths

gas ingas outSlide12

Ongoing challenges

Ground state spectrum

Overcoming instrument drift during sample switching

Transient spectrum

Maximizing signal to noise ratio

Avoiding photodeposition12

gas in

gas outSlide13

Summary

13

X-ray spectroscopy with high accessibility and high time resolution

Development of liquid phase compatibility

Electronic structure of transition metal catalystsSlide14

Acknowledgements

14

Prof. Josh

Vura

-Weis

Vura

-Weis group

Ryan,

Muffaddal

, Michaela, Sean, Suds, Ming-Fu, Liz,

Yusef

,

Aastha, Kori, Max, Kaili

Funding

AFSOR YIP

UIUC Start-up Fund

NSF CAREER Slide15

M-edge spectroscopy has element, oxidation- and spin-state, and ligand field specificity.

15

Zhang, K.,

et. al. J

. Phys. Chem. Lett.

  2016, 7, 3383-3387.

Oxidation state

Ligand field

Spin state

Experiment

SimulationSlide16

What else is known about DuBois’ catalyst?

16

31

P NMR

–examination of

diamagnetic Ni(0)

and

Ni(II) shows

that the complex can get “stuck” in certain conformers (Bullock 2013)EPR –examination of paramagnetic Ni(I) state shows that the hydride adduct does not form for this oxidation state (Van

Gastel 2014)Stop flow kinetics –isolation of the Ni(II)

hydride adduct (Dempsey 2015)tr-XAS –observation of the first

step in the proposed cycle (Mulfort 2016)Bullock, R. M. J. Am. Chem. Soc.

2013,

135,

9700-9712.

van

Gastel

, M.

J. Phys. Chem. C.

2014,

118,

2350-2360

.

Dempsey, J. L.

J. Am. Chem. Soc.

2015

,

137

, 13371-13380.

Mulfort

, K.L.

J. Phys. Chem. C

 

2016,

120, 20049-20057.

Slide17

Effects of sample inhomogeneity in tabletop XUV spectroscopy

Spatial chirp

17

Sample inhomogeneity on scale of beam size

Lin, M.-F.,

et. al.

J

. Opt. Soc. Am. B

33,

1986-1992 (2016)Slide18

Liquid cell pump probe spectroscopy

18Slide19

19

Valence

K-edge

L-edge

M

-edge

1s

2s, 2p

3

s, 3p

~500-1,000 eV

~1,000-10,000 eV

~30-100 eVSlide20

HHG conditions can be tuned to output an XUV continuum.

20

Mn

Fe

Co

NiSlide21

21

~10-100 nm sample

Silicon nitride substrate

Silicon wafer support

100 µmSlide22

Adjusting the gas pressure allows for a tunable pathlength.

22

A

)

B)

C)

D)

100 µm

100 µm

100 µm

100 µm

Transmission at different

pathlengths

Images of window at corresponding

pathlengths