Users bring a wide range of samples to Diamond’s Versatile Soft X-ray (VERSOX) beamline, including heterogeneous catalysts, pharmaceuticals and biomaterials for study under realistic conditions, liquids and ices for environmental and space science studies, heritage artefacts, electronic and photonic materials. The common factor in these experiments is a desire to explore the chemical nature and composition of the near-surface regions of the samples, using soft X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. VERSOX also provides non-standard sample environments and detection techniques that are uncommon at synchrotrons. In two papers, recently published in the Journal of Synchrotron Radiation and Journal of Physics: Energy, the beamline staff explore the capabilities of this versatile beamline, and a new spectro-electrochemical flow cell developed in-house that allows fast sample change and membrane replacement for XPS/XAS measurements.
Soft X-ray and X-ray absorption spectroscopy (XAS), also called near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy and X-ray photoelectron Spectroscopy (XPS), allow researchers to collect elemental, chemical and structural information about solids, liquids and gases. These techniques are also ideal for probing the interfaces between these phases (e.g. solid-gas, solid-liquid, liquid-vapour) and local interactions at the surfaces and in sub-surfaces of materials.
Soft X-ray NEXAFS is a versatile analytical tool for a broad range of applications spanning fundamental and applied research, including catalysis, batteries and electrolytes, local bonding of organic molecules in crystals and speciation in solution and geochemistry. Studies conducted at near-ambient pressure allow operando or in-situ analysis of materials.
Diamond’s VERSOX beamline (B07) now comprises two separate branches, with a total of three endstations, allowing studies of a wide range of interfaces and materials. Experiments can be conducted at ambient pressure, or in an extended pressure range from 1 x 10-10 mbar to 1 x 103 mbar. The beamline and endstations use advanced software controls to maximises sample throughput and ease-of-use.
Principal Beamline Scientist Georg Held said:
B07 is really two beamlines, delivering 48 hours of beam to users per day. B07-C, which has been in operation since 2017, is designed for X-ray photoelectron spectroscopy (XPS) studies at ambient pressure (up to ~50 mbar). The new B07-B branch has two endstations. The first (ES-1) is for high-throughput XPS and near-edge X-ray absorption fine-structure (NEXAFS) measurements under ultra-high vacuum (UHV) conditions. It hosts a lot of cell activities, with users bringing battery cells, electrochemical cells, or high-pressure cells to do experiments. The second (ES-2) is dedicated to NEXAFS at pressures from UHV to ambient pressure, with relatively fast sample exchange.
ES-2 provides specialised sample environments, including a low-cost, reliable microreactor for heterogeneous catalysis and an operando electrochemical cell.
Senior Beamline Scientist Dave Grinter said:
We've got a variety of endstations and sample environments and we aim to cover as wide a range of conditions as we can, ranging from the traditional ultra-high vacuum, low temperature surface science on model systems all the way up to a cell for liquid-solid interactions. We try and automate as many of the measurements as possible, to achieve high throughput. Another aspect of that is making the measurements really easy to do, scriptable, and accessible for users that are not necessarily experts in in NEXAFS and XPS, making the facility available to a much wider user group. We also have the high-pressure gas microreactor, developed in collaboration with a long-term user group from the University of St. Andrews. It’s designed for looking at catalysts at high temperatures (400°C) under one bar pressure, so more realistic industrial conditions.
For operando/in situ near ambient pressure (NAP) soft X-ray XPS and NEXAFS studies, suitable reaction cells enable users to track the chemical state and structural properties of catalytically active materials under realistic reaction conditions. At B07 beamline, an electrochemical flow cell was developed in collaboration with Redox.me for operando X-ray spectroscopy of liquids and electro(photo)catalysts. This work was funded by the European commission via a Horizon2020 grant, HySolChem Project.
Beamline Research Associate Santosh Kumar said:
The new sample environment we developed in-house is related to electrochemistry research. It allows us to probe a wide range of electrochemical systems, including water and CO2 electrolysers, fuel cells, batteries, and electrosynthesis of fine chemicals. For instance, electrolysis of water, producing hydrogen by splitting water. With the current focus on replacing fossil fuels with more sustainable energy sources, one of the potential options is called green hydrogen, and that’s hydrogen produced using renewable electricity. At the moment, that’s not an affordable option, and one of the challenges is the durability of the catalyst used during the reaction. So our cell allows us to look at these fundamental challenges and probe the structure and the interface of the catalyst and the electrolyte in the cell in real-time during reaction. This new research capability opens up exciting opportunities for the B07 beamline user community, both academic and industrial.
Grinter DC et al. VerSoX B07-B: a high-throughput XPS and ambient pressure NEXAFS beamline at Diamond Light Source. Journal of Synchrotron Radiation 31.3 (2024). DOI:10.1107/S1600577524001346.
Kumar S et al. An electrochemical flow cell for operando XPS and NEXAFS investigation of solid-liquid interfaces." Journal of Physics: Energy (2024). In press DOI:10.1088/2515-7655/ad54ee.
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