Spectro-electrochemistry using X-ray absorption spectroscopy on a tabletop X-ray machine

Abstract

To study Si and Fe based microwires coated with TiN we will need to design and test
a cell on a tabletop X-ray setup called easyXAFS300. To do this we have developed a
X-ray absorption spectroscopy spectroelectrical (XAS-SEC) cell. To test the easyX-
AFS300 equipment on the soft part of the X-ray spectrum we have cooperated with
Hang Yin to measure a Lanthanum halide compound Cs3LaCl6. These compounds
are interesting for there luminescence properties and are thought to have a use as
X-ray scintillators. It has been shown in previous XPS measurements that In dopant
will cause a structural change in this compound. We seek to determine this in a x-ray
near edge spectroscopy (XANES) measurement. To measure these microwires we also
need to be able to make XAS-SEC measurements where we have looked at different
designs for a XAS-SEC cell and design our own 3D-printed version. For our XAS-SEC
measurement we have a potassium iron hexacyanide compound where we induce a ox-
idation change electrochemically and measure that change in a XANES measurement.
For this thesis I have done a course to learn how to preform X-ray absorption measure-
ments (XAS) at MaxIV and how to preform electrochemical measurements as well as
how to make 3D designs. We were able to preform our lanthanum measurement but
unable to confirm previous XPS measurements. While we had several problems with
leaks and water absorption of our 3D-printed XAS-SEC cell. We where able to in-
duce a electrochemical change and measure that change with XANES measurements
despite not being in electrochemical control. This show that with a better designed
cell that these measurement are possible on Si and Fe based micorwires.

Popular Abstract

Silicone microwires is a promising material for solar-driven hydrogen production via
water splitting. To engineer efficient catalysts for their surface coatings, we must
study their electronic and oxidation states in real time under in situ conditions. X-ray
Absorption Spectroscopy (XAS) specifically X-ray Absorption Near Edge Structure
(XANES) is an ideal tool for this task.

In XANES measurements the photons interact with the inner electrons of a target
element where the core electron absorb photons and are excited to a unoccupied
electronic state. When a photon is absorbed by the inner most shell then this is
called the K-edge. XANES focuses on the first main peak in a XAS spectrum called
the whiteline where changes in electronic state and oxidation state can be observed.
For titanium the K-edge is at 5 keV. As attenuation for matter increases with lower
X-ray energies in accordance with Beer-Lamberts law. This makes water and air
absorption a challenge for titanium measurements.

To better understand how to mange these low energy X-ray conditions before introducing
a liquid setup we collaborated with a researcher called Hang Yin to preform
transmission measurements on lanthanum samples which has a similar energy for its L-edge.
These samples where pressed into pellets where we encountered problems with microscopic
cracks called ”pin-holes” leading to long attenuation times where a single measurement
took 20 hours. While no change dependent on impurities was observed it proved valuable
for learning about our setup.

From the lanthanum measurements as well as our understanding of soft X-ray measurements
we made a 3d-printable XAS-SEC cell which is inspired by the design made by Paparoni et al.
Where the use of a screw design to adjust the distance between the window and the sample.
Several iterations of the cell was made to test the seals and material used.

To test the cell potassium ferricyanide was dissolved in water and pumped trough the
cell. To check the electrochemical components a cyclic voltammetry measurements
was preformed. Our potentiostat was not able to measure the current during the entire
cyclic voltammetry measurements which limited the potentioal that could be applied
during the XAS-SEC measurement. During the XAS-SEC two different potentials
was applied to the solutions which oxidized or reduced the sample which caused a
∼1 eV shift in the spectrum. This shows that the sample has been
oxidized and reduced successfully and we where able to measure this change in our
XAS setup.

The prototype cell demonstrated the concept, future iterations will focus on solving
minor leaks encountered while measuring and integrate a potentiostat that can handle
larger currents. Once optemized the cell can be used to measure iron and titanum
coated silicone microwires.

• author: Roos, Johan
• supervisor: Axl Eriksson
• organization: Department of Chemistry
• course: KEML10 20252
• year: 2026
• type: M2 - Bachelor Degree
• subject: Chemistry
• keywords: microwires, spectroelectrochemistry, tabletop X-ray device, XANES, XAS, physical chemistry
• language: English
• id: 9248476
• date added to LUP: 2026-08-18 10:05:11
• date last changed: 2026-08-18 10:05:11