Tag: X-ray absorption spectroscopy

#SynchroLightAt75 – Historical perspective of catalysis at Elettra

#SynchroLightAt75 – Historical perspective of catalysis at Elettra

“Catalysis, is a strange principle of chemistry which works in ways more mysterious than almost any other of the many curious phenomena of science” New York Times: June 8, 1923

Heterogeneous catalysis is one of the most extensively studied functional systems since it is in the heart of chemical industry, fuel, energy production and storage and also is part in the devices for environmental protection.

The key processes in heterogeneous catalysis occur at dynamic reactant/catalyst surface interfaces. Since these processes involve coupling between different electronic, structural and mass transport events at time scales from fs to days, and space scales from nm to mm, we are still far from full comprehension how to design and control the catalysts performance. In this respect the ultrabright and tunable light, generated at the synchrotron facilities, has opened unique opportunities for using powerful spectroscopy, spectromicroscopy, scattering and imaging methods for exploring the morphology and chemical composition of complex catalytic systems at relevant length and time scales and correlate them to the fabrication or operating conditions.

The very demanded for catalysis studies is the surface sensitive PhotoElectron Spectroscopy (PES), based on the photoelectric effect, for which Einstein won the 1921 Nobel Prize in Physics, and demonstrated for the first time in 1957 by Kai Siegbahn who was awarded the Nobel Prize in 1981. PES has overcome its time and space limitations for studies of catalytic surface reactions thanks to the synchrotron light, which also added the opportunity for complementary use of X-ray absorption spectroscopy. At Elettra, the first time resolved PES studies with model metal catalyst systems were carried out at SuperESCA beamline in 1993 and few years later PES microscopy instruments, Scanning PhotoElelectron Microscope (SPEM) and X-ray PhotoElectron Emission Microscope (XPEEM) at ESCAMicroscopy and Nanospectroscopy beamlines have allowed for sub-mm space resolved studies, including imaging of dynamic surface mass transport processes as well.

Implementation in the last decade of operando experimental set-ups at APE, BACH and ESCAMicroscopy experimental stations for bridging the pressure gap of PES investigations has led to significant achievements in monitoring in-situ chemical, electrochemical and morphology evolution of all types catalytic systems under reaction conditions. Further complementary studies using X-ray absorption spectroscopy in photon-in/photon-out mode, ongoing at the XAFS and TwinMic beamlines are filling some remaining knowledge gaps for paving the road towards knowledge-based design and production of these complex and very desired functional materials.

M. Amati, L. Bonanni, L. Braglia, F. Genuzio, L. Gregoratti, M. Kiskinova, A. Kolmakov, A.Locatelli, E. Magnano, A. A. Matruglio, T. O. Menteş, S. Nappini, P. Torelli, P. Zeller,” Operando photoelectron emission spectroscopy and microscopy at Elettra soft X-ray beamlines: from model to real functional systems”, J. Electr. Spectr. Rel. Phenom. (2019) doi: 10.1016/j.elspec.2019.146902.

For first SUPERESCA – A. Baraldi, G. Comelli, S. Lizzit, M. Kiskinova, G. Paolucci “Real-Time X-Ray Photoelectron Spectroscopy of Surface Reactions” Surf. Sci. Reports 49, Nos. 6-8 (2003) 169.

For XPEEM A. Locatelli and M. Kiskinova “Imaging with Chemical Analysis: Adsorbed Structures Formed during Surface Chemical Reactions” A European Journal of Chemistry, 12 (2006) 8890.

Image: From model to real catalysts: structural and chemical complexity

Opening Ceremony for the new ASTRA (SOLABS) beamline

Opening Ceremony for the new ASTRA (SOLABS) beamline

On 29 June 2022, the official opening ceremony was held for the ASTRA beamline (formerly SOLABS), a beamline dedicated to measurements using X-ray absorption spectroscopy (XAS) in the energy range of 1 keV to 15 keV. The ceremony was attended by a number of distinguished guests along with the international team involved in building the beamline.

International cooperation is the key to success.

The ASTRA beamline was created thanks to the cooperation of 4 scientific institutions, the Hochschule Niederrhein University of Applied Sciences (Germany), Synchrotron Light Research Institute (Thailand), the Institute of Physics at Bonn University (Germany), and the SOLARIS Center.

Read more on the Solaris website

Image: Starting from right to left: Prof. Alexander Prange (Hochschule Niederrhein), Dr Thomas Grünewald (Hochschule Niederrhein), Prof. Stanisław Kistryn (Jagiellonian University), Prof. Marek Stankiewicz (SOLARIS, JU), Dr Michael Groß (Consul General of Germany), Prof. Josef Hormes (University of Bonn). Further Dr Alexey Maximenko (SOLARIS), Dr Henning Lichtenberg (Hochschule Niederrhein), Marcel Piszak (SOLARIS) – credit Solaris Synchrotron. 

Carbon nanospheres for improved sodium-sulfur batteries

Carbon nanospheres for improved sodium-sulfur batteries

Sodium-sulfur batteries are promising electrical energy storage technologies that can serve as a key solution to intermittency problems and can be integrated with renewable forms of energy generation. An international research team has reported the synthesis of micro-mesoporous carbon nanospheres with continuous pore distribution as an efficient sulfur host for sodium-sulfur batteries. The work sheds new light on the progress of the sulfur cathode in sodium-sulfur batteries and provides a promising strategy for the viable design of other metal–sulfur batteries. Experiments at the CLAESS beamline in ALBA allowed determining the sulfur species during charge/discharge processes.

Solar and wind power are useful resources for energy generation but they are intermittent (at night or on cloudy days solar panels do not work, for example). Electrical energy storage technologies serve as a key solution to these intermittency problems and can be integrated with renewable forms of energy generation. Among these technologies, room-temperature sodium-sulfur (Na–S) batteries are deemed to be one of the most promising candidates, owing to their high theoretical energy density – the amount of energy they can store – and low cost. Nonetheless, this battery system suffers from a slow reaction rate at room temperature, which radically limits battery performance and makes difficult its practical commercialization.

An efficient strategy to deal with this challenge is the use of porous carbon material as a host to encapsulate molecular sulfur, significantly enhancing its conductivity. This system acts as the cathode of the battery, which is the electrode where reduction occurs. To make the battery work, sodium ions have to migrate from the anode to the cathode. However, in these systems, it is a challenge to provide fully accessible sodium ions that do not obstruct the sub-nanosized pores of the carbon host.

In a publication in the Advanced Materials journal, an international research team made up of Australian and Chinese institutions in collaboration with the ALBA Synchrotron has reported the synthesis of micro-mesoporous carbon nanospheres (MMPCS) with continuous pore distribution as an efficient sulfur host for sodium-sulfur batteries. This unique feature creates continuous channels that allow the movement of sodium ions without channels being obstructed. This enables a high conductivity, leading to fast sulfur reduction-oxidation reaction during the charge/discharge processes.

Read more on the ALBA website

New techniques available at SOLARIS synchrotron

New techniques available at SOLARIS synchrotron

From 2022, National Synchroton Radiation Center SOLARIS provides access to two new research techniques. Access to the Scanning Transmission X-ray Microscope and X-ray Absorption Spectroscopy beamline optimized for measurements in the soft and tender energy range, will be possible in the next call for proposals, in March 2022.

Scanning transmission X-ray microscopy (STXM) is a method to obtain a microscopic image of the raster-scanned sample by detecting the transmission intensity of the focused X-rays. The STXM is one of the two end stations of the DEMETER beamline in NSRC SOLARIS. The operating principle of the STXM is scanning of the sample in the focus of the Fresnel zone plate, which for this device is the lens focusing X-rays. In the next step, the detector measures the intensity of the radiation passing through the sample and, on the basis of the intensity images recorded by the detector, it is possible to calculate the absorption X-ray radiation in a selected place of the tested system. The most important measurement mode in STXM is the so-called “image stack” – a series of images are collected as a function of photon energy to obtain a dataset with space (XY) and energy (E) dimensions. A local absorption spectrum can be obtained from the arbitrary region of interest at the image. It allows a detail chemical composition analysis of a measured sample. The source for the STXM end station is elliptically polarized undulator, which enables to cover the energy range from 100 to 2000 eV. The undulator allows measurements using linear, circular and elliptical polarization. Detailed information about the STXM end station you can find here: https://synchrotron.uj.edu.pl/en_GB/linie-badawcze/demeter/STXM.

X-ray Absorption Spectroscopy beamline – SOLABS is a bending magnet beamline dedicated to X-ray absorption spectroscopy (XAS) in the energy range from 1 keV to 15 keV. The beamline was especially designed for XAS measurements in the tender X-ray range, i.e., at the K absorption edges of important elements such as P, S, Si, Al and Mg. Besides, the energy range also includes K-edges of heavier elements up to Se, L-edges of elements up to Bi and some M-edges of elements including U, which allows investigation of a variety of highly relevant materials. Due to this straightforward concept without any optical components such as lenses or mirrors, SOLABS can be quickly aligned and easily operated.  At the beamline spectroscopic experiments in different measurement modes and with various sample environments are possible. XAS is a non-destructive, element-specific characterization method that can be applied to both crystalline and amorphous materials, liquids and samples in the gas phase. Detailed information about the SOLABS beamline and the features of its end station can be found here: https://synchrotron.uj.edu.pl/en_GB/linie-badawcze/solabs

Agnieszka Cudek

The Head of Communication, SOLARIS National Synchrotron Radiation Centre

To apply for beamtime, please visit the SOLARIS website

Silver nanoparticles for the elimination of ammonia released to the atmosphere

Silver nanoparticles for the elimination of ammonia released to the atmosphere

Researchers from the ITQ-UPV-CSIC, in collaboration with ALBA, have explored the use of silver nanoparticles as catalysts for the selective catalytic oxidation of ammonia, one of the main atmospheric pollutants. Thanks to the CLÆSS beamline at ALBA, researchers proved that the active catalyst for the reaction of ammonia to nitrogen and water is metallic silver, instead of silver cations. These findings will contribute to developing new methods for the elimination of ammonia released to the atmosphere in industry and in diesel vehicles.

Ammonia is one of the main atmospheric pollutants and damages both the human health and the environment. Most ammonia emissions come from fertilizers used in agriculture, but it is also released to the atmosphere in biomass burning, fuel combustion and industrial processes, in which unreacted ammonia escapes into the atmosphere in the exhaust gases.

In the last years, more strict environmental regulations have been intensified with the aim to develop new methods for the elimination of this pollutant. The most promising technology is the selective catalytic oxidation of ammonia to nitrogen and water.

In a recent publication, researchers from the Instituto de Tecnología Química, Universitat Politècnica de València – Consejo Superior de Investigaciones Científicas (UPV-CSIC), in collaboration with ALBA, have explored the use of silver-containing zeolites (microporous aluminosilicates) for the catalytic oxidation of ammonia. Results confirmed that the active site for the reaction is the silver found in the form of metallic nanoparticles at the external surface of the zeolite, whereas silver cations (Ag+)are practically non-active.

Furthermore, the experiment proved that silver nanoparticles present in the active catalyst were dispersed and oxidized to silver cations during the reaction. These findings will allow the scientific community to develop a method for removing ammonia released to the atmosphere in industry and in diesel vehicles.

The experiment, performed at the CLÆSS beamline in the ALBA Synchrotron, allowed to study the catalysts under reaction conditions. The researchers recorded several X-ray absorption spectra (XAS) while submitting the samples to the reactive atmosphere (ammonia and oxygen) at increasing temperatures. Results showed that the silver nanoparticles formed before the reaction were dramatically modified under reaction conditions, being most of them dispersed and resulting in small clusters and cations Ag+.

Read more on the ALBA website

Image: NH3-SCO reaction pathway using Ag-Zeolites

Scientists tackle indoor air pollution

Scientists tackle indoor air pollution

People on average spend nearly 90% of their time indoors and, especially in the cold winter months in Canada, this statistic can be even higher. With all that time spent indoors, filtering out pollutants from indoor air is very important for the health of Canadians.

Researchers from the College of Engineering at the University of Saskatchewan (USask) have been developing a catalyst for a new type of air purifying technique that would clean air at room temperature.

“Ozone is one of the strongest purifying agents that has been used in the water treatment industry for a long time. In our research, we use ozone and an effective catalyst to purify indoor air from Volatile Organic Compounds or VOCs,” explained PhD student Mehraneh Ghavami.

Ghavami and co-researcher Dr. Jafar Soltan used the HXMA beamline at the Canadian Light Source (CLS) at USask to discover which types of metal catalysts would work best for eliminating pollutants out of the air and recently published their findings.

Their air purifying system uses ozone gas and a catalyst to remove indoor air pollutants and turn them into carbon dioxide and water.

Read more on the Canadian Light Source website

Image: Mehraneh Ghavami using the CLS’ HXMA beamline

Credit: CLS

Unravelling the history of 15th Century Chinese porcelains

Unravelling the history of 15th Century Chinese porcelains

Researchers from French and Spanish Institutions used the combination of two synchrotron light characterization techniques to study Chinese blue-and-white Ming porcelains. They were able to identify the firing temperature by determining the porcelain’s pigments and the reduction-oxidation media conditions during their production. The approach they used can also be applied on a broad range of modern and archaeological ceramics to elucidate their production technology.

Pottery is found at the majority of archaeological sites dating from the Neolithic period, when first human settings appear, onwards. Which makes it a major focus of study in archaeological science.  The study of style and production of ceramics is central to the historical reconstruction of a site, region and period.

More specifically, ceramic technological studies look to reconstruct the production technology of ceramics, by determining the selection and preparation of the raw materials, the formation of ceramics, treatment and decoration of the ware’s surface and the firing atmosphere. All of this is possible thanks to the scientific techniques available nowadays.

In a recent publication, researchers from French and Spanish Institutions used the combination of two synchrotron light characterization techniques to study Chinese blue-and-white Ming porcelains. These characteristic porcelains, whose production flourished around the 14th century, are decorated under the glaze with Cobalt-based blue pigments that provided their distinctive blue decorations and produced during a one-step firing at high temperatures.

They were able to identify the firing temperature by determining the porcelain’s pigments and the reduction-oxidation media conditions during their production. The approach they used can also be applied on a broad range of modern and archaeological ceramics to elucidate their production technology.

Read more on the ALBA website

Image: Porcelain Jar with cobalt blue under a transparent glaze (Jingdezhen ware). Mid-15th century

Credit: Metropolitan Museum of Art.

Fe Cations Control the Plasmon Evolution in CuFeS2 Nanocrystals

Fe Cations Control the Plasmon Evolution in CuFeS2 Nanocrystals

Research on the synthesis of CuFeS2, an exciting semiconductor, outlines a method to verify its phase purity and investigate its properties.

Plasmonic semiconductor nanocrystals have become an appealing avenue for researching nanoscale plasmonic effects due to their wide spectral range (visible to infrared) and great tunability compared to traditional precious metal nanocrystals. CuFeS2 is an exciting semiconductor that has a prominent plasmon absorption band in the visible range (∼498 nm). In this work, the researchers determined the origin of the plasmonic behaviour in CuFeS2 by characterizing the nucleation and growth stages of the reaction through a series of ex situ and in situ probes (e.g., X-ray absorption spectroscopy and X-ray emission spectroscopy). They showed that the plasmon formation is driven by band structure modification from Fe(II) incorporation into the nanocrystals. Mixed oxidation state of Cu(I)/Cu(II) and Fe(II)/Fe(III) was observed.  Using these results, the researchers proposed a reaction mechanism for synthesis of CuFeS2 and outlined a method to verify the phase purity of the material.

Read more on the CHESS website