Tag: catalysis

Unveiling finer details in the physics of materials

Unveiling finer details in the physics of materials

Scientists at the European XFEL’s SCS instrument routinely use a technique called transient X-ray absorption spectroscopy (XAS) to investigate materials that have applications in data storage and processing, catalysis, or in the search for room temperature superconductors. Investigating very small changes in the motion of electrons within a material’s structure on ultrashort timescales provides scientists with fingerprints of the complex processes at play within them. This helps them characterise samples that are important for energy and materials research.

Using the European XFEL’s brilliant pulses, researchers can overcome some of the issues of conventional transient XAS—such as long measurement times—but the varying intensity of European XFEL’s pulses provides its own challenges. Now, scientists at SCS have implemented a new sampling scheme for improving the efficiency of such measurements.

Read more on the European XFEL website

Image: The X-ray beam is split into three copies. Two of these copies are passed through identical samples of the material under investigation, with one of these samples also being illuminated by a laser (‘optical laser’ in the figure). This transforms it into a new state, interesting to researchers. From this, scientists are able to ‘subtract’ detrimental noise, revealing the finest details of the sample under investigation.

Graphene coated nickel foams for hydrogen storage

Graphene coated nickel foams for hydrogen storage

Hybrid composites where graphene (Gr) and other 2D materials replicate the meso-and micro-structure of 3D porous substrates have shown innovative functionalities in catalysis and energy-related fields. Concerning hydrogen storage, the high surface-to-volume ratio exhibited by both 2D and 3D components of the hybrid material is expected to increase the efficiency of surface chemisorption and bulk absorption of hydrogen in comparison to the flat counterparts. To explore this possibility, we have grown single layer Gr on porous nickel foams and have investigated the interaction with H atoms as a function of the temperature by using X-ray photoelectron spectroscopy and thermal programmed desorption (TPD) at the SuperESCA beamline of Elettra.

The growth of Gr on the Ni foam was obtained by exposing the sample at 773 K to ethylene. Selected C 1s spectra taken at increasing growth time are shown in Fig.1a. Upon exposure to ethylene, the carbide phases (N1-N4 components) observed in the pristine sample disappear, while new Gr components (labeled C0 and C1) progressively increase in intensity and eventually saturate. The component C0 is attributed to GrS regions grown on the (111) foam grains, where the interaction with the support is as strong as that between Gr and the ordered Ni(111) surface; C1 is attributed to GrW regions that are rotated with respect to (111) grains, or are grown on Ni grains exposing different orientations, and therefore, are interacting weakly with the support.

Read more on the Elettra website

Figure 1: a) C 1s spectra measured during the Gr growth after 0, 3,10,16 and 44 minutes of exposure to ethylene at 773 K and (bottom) at RT after growth; b) C 1s spectra acquired on the Gr/foam hydrogenated with the same H dose at the indicated temperatures TH and c) TPD curves measured during sample annealing.

Fig. 1b shows the C 1s spectra measured on the Gr/foam exposed to a flux of H atoms at temperatures TH between 78 and 298 K. Starting from TH=98 K, the C 1s line shapes appear broadened on the high binding energy (BE) side, due to the appearance of a component (labeled A) at 285.0 eV, and also on the low BE side, due to another component (labeled B) at 284.1 eV. A and B are ascribed to C atoms directly bonded to H atoms and to their first neighbors, and therefore indicate the occurrence of H chemisorption on Gr. From 198 K, some intensity is transferred from C0 to C1, because at this temperature the H atoms start to intercalate below GrS, which detaches gradually from the substrate. The intercalation under the nearly free-standing GrW remains undetected, because here the penetration of H underneath does not cause any measurable extra-shift of the C1 component.

Fig. 1c shows H2 TPD curves measured while heating the Gr/foam hydrogenated at increasing TH. The desorption of H atoms chemisorbed on Gr originates solely the weak peak G at ~ 650 K.  Hence, all other TPD features correspond to the desorption of H atoms intercalated below Gr and residing at the Ni foam surface or even diffused into the Ni bulk. Hence, differently from GrS, where H atoms intercalate only for TH ~ 198 K, intercalation below GrW occurs at much lower temperatures. The TPD curves up to TH=173 K are dominated by the D peak, due to the desorption of H atoms penetrated in metastable subsurface sites of the Ni foam. The H2 release at higher temperatures is related to the slower desorption of bulk H atoms and to the release of H atoms chemisorbed on the Ni surface. It turns out that the highest quantity of loaded hydrogen is detected for TH= 113 K and amounts to ~ 5 times the quantity which saturates the Ni (111) surface with equivalent macroscopic lateral dimension.

Success from widening access to basic science research tools and synchrotron expertise in Africa

Success from widening access to basic science research tools and synchrotron expertise in Africa

A focus of UNESCO’s International Year of Basic Sciences for Sustainable Development is ‘enhancing inclusive participation in science’. Diamond Light Source was a key partner in START, a collaborative project that sought to foster the development of Synchrotron Techniques for African Research and Technology (START), which ran from 2018 to 2021 with a £3.7 M grant from the Global Challenges Research Fund (GCRF) provided by the UK’s Science and Technology Facilities Council (STFC). Today on World Science Day for Peace and Development, we are highlighting health and energy research enabled by START.

Diamond played a pivotal role in the project, providing African scientists with crucial access to world class synchrotron techniques, beamtime, training and mentoring. Research focused on structural biology and energy materials to address key United Nations’ Sustainable Development Goals for health (SDG 3), energy (SDG 7), climate (SDG 13), and life-long learning (SDG 4).

Addressing worldwide energy challenges

Catalysis is essential for the development of a sustainable world and was a focus of the energy materials arm of the grant, along with solar energy, which is a well-recognised sustainable energy solution. These are just two areas in the physical sciences that were investigated as part of START.

Working towards better renewable energy solutions

Catalysis has many applications in renewable energy, where waste biomass is converted to liquid biofuels, or waste CO2 is converted to high value chemicals that can be used in our daily life, or as an alternative to fossil fuels. These applications rely on catalysts but to make this process more sustainable and efficient, advanced techniques are required to understand how the catalysts work under operating conditions. A group of START collaborators used Diamond to understand more about catalyst materials. They were investigating furfural, a bio-derived molecule that can be converted to many useful products that can be used for renewable energy. However, bio-derived compounds are highly functionalised – many parts of the molecular structure can undergo chemical change. Palladium (Pd) nanoparticles are widely used as an active component in furfural hydrogenation – a specific type of reaction that involves the addition of hydrogen to a compound – however, selectivity to specific products is a big challenge. Using X-ray absorption spectroscopy at Diamond, the team demonstrated that a Pd/NiO catalyst can hydrogenate furfural using a dual site process. This work has significant implications for the upgrading of bioderived feedstocks, suggesting alternative ways for promoting selective transformations and reducing the reliance on precious metals.

Read more on the Diamond website

Image: START logo

High entropy alloys: structural disorder and magnetic properties

High entropy alloys: structural disorder and magnetic properties

High-entropy alloys (HEAs) are promising materials for catalysis and energy storage, and at the same time they are extremely hard, heat resistant and demonstrate great variability in their magnetic behaviour. Now, a team at BESSY II in collaboration with Ruhr University Bochum, BAM, Freie Universität Berlin and University of Latvia has gained new insights into the local environment of a so-called high-entropy Cantor alloy made of chromium, manganese, iron, cobalt and nickel, and has thus also been able to partially explain the magnetic properties of a nanocrystalline film of this alloy.

High entropy alloys or HEAs consist of five or more different metallic elements and are an extremely interesting class of materials with a great diversity of potential applications. Since their macroscopic properties are strongly dependent on interatomic interactions, it is utterly interesting to probe the local structure and structural disorder around each individual element by element-specific techniques. Now, a team has examined a so called Cantor alloy – a model system to study the high-entropy effects on the local and macroscopic scales.

Read more on the HZB website

Image: The Cantor alloy under study consists of chromium (grey), manganese (pink), iron (red), cobalt (blue), and nickel (green). X-ray methods allow to probe each individual component in an element-specific way.

Credit: © A. Kuzmin/University of Latvia and A. Smekhova/HZB

European Young Chemists’ Award for Sebastian Weber

European Young Chemists’ Award for Sebastian Weber

In recognition of Sebastian’s PhD thesis on hard X-ray microscopy, tomography, and application of synchrotron radiation in catalysis research

Sebastian Weber, a recent PhD graduate at the Institute for Chemical Technology and Polymer Chemistry (ITCP) / Institute for Catalysis Research and Technology (IKFT) at Karlsruhe Institute of Technology (KIT), was awarded the Gold Medal in the PhD category of the European Young Chemists‘ Award. The award is presented every two years during the EuChemS Chemistry Congress on behalf of the Società Chimica Italiana (SCI) and the European Chemical Society (EuChemS). The prize highlights excellent research from young / early stage researchers across all fields of chemistry and chemical sciences. During his PhD phase, Sebastian Weber studied materials used in heterogeneous catalysis with a broad range of spatially-resolved X-ray characterisation methods, in order to gain a deeper understanding of the structure and function of catalysts. The project made extensive use of synchrotron radiation, specifically X-ray microscopy and tomography as emerging methods in catalysis research. This success on the European level highlights the leading role which synchrotron science has to play in the study of matter.

Catalysis plays a crucial role in sustainable chemical production, chemical energy conversion and storage, among many others, and is a key technology area in synchrotron radiation research. During his PhD work at Karlsruhe Institute of Technology, Sebastian Weber studied catalysts for CO2 methanation using spatially-resolved characterisation tools including X-ray microscopy and tomography. These diverse X-ray imaging methods were exploited to study the 3D structure of catalytic materials over a range of length scales, addressing various levels of hierarchical structural features which are critical to understanding catalyst performance. This topic is a special focus of the Young Investigator Group of Dr. Thomas Sheppard at KIT, who supervised and secured funding for the project, within the wider group of Prof. Jan-Dierk Grunwaldt.

Only a handful of research groups worldwide are currently active in the field of X-ray microscopy applied to catalysis research, highlighting the emerging role of this vibrant research field. During his PhD work, Sebastian Weber in particular worked to develop applications of hard X-ray ptychography and ptychographic X-ray tomography (PXCT) to study catalyst pore structures, structural evolution under reaction conditions, and the effects of catalyst deactivation. These methods routinely reach spatial resolution below 50 nanometres (0.001 x diameter of a human hair), and have been applied so far on samples up to 50 micron in diameter (ca. the diameter of a human hair). The further development of ptychography holds excellent potential for catalysis and materials research, particularly in the age of fourth generation light sources with improved coherence and decreased source emittance. The project resulted in several high quality publications in leading chemistry and materials journals, reflecting the knowledge gained regarding 3D structure of catalysts, and the potential for development of improved catalysts in future.

Sebastian Weber recently completed his doctorate with the title “Revealing Porosity and Structure of Ni-based Catalysts for Dynamic CO2 Methanation with Hard X-rays”, earning a distinction from KIT. Now his work was further recognised by securing the Gold Medal of the European Young Chemists’ Award at PhD level. The award is presented every two years during the EuChemS Chemistry Congress on behalf of the Società Chimica Italiana (SCI) and the European Chemical Society (EuChemS). The prize highlights excellent research from young / early stage researchers across all fields of chemistry and chemical sciences, and is therefore a highly competitive prize. After a pre-selection phase based on scientific excellence, the six finalists each held a presentation at the EuChemS Chemistry Congress in Lisbon, Portugal. The award not only highlights the excellent contribution of Sebastian Weber to the field of chemical sciences, but promotes in front a broad audience the essential role of synchrotron radiation in delivering future insights and innovations across the field of natural sciences.

Related articles on this research can be found in the Diamond Annual Review 2021-2022, “X-ray ptychography investigates coking of solid catalysts in 3D”, p.66-67, and on the DESY website

Image: Award ceremony during the 8th EuChemS Chemistry Congress in Lisbon, Portugal, Sebastian Weber (KIT, left), Prof. Floris Rutjes (President of the European Chemical Society, middle) and Prof. Angela Agostiano (Chair of the EYCA Award Committee, right).

Graphics: EYCA

#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

Lightsources.org virtual symposium recording

Lightsources.org virtual symposium recording

Lightsources.org was delighted to welcome over 500 attendees to our live virtual symposium to mark the 75th Anniversary of the first direct observation of synchrotron light in a laboratory. The event, which was chaired by Sandra Ribeiro, Chair of lightsources.org and Communications Advisor for the Canadian Light Source, was held on the 28th April 2022 and you can watch the recording via the YouTube link below.

We received some lovely feedback after the live event, including this comment from Jeffrey T Collins at the Advanced Photon Source, Argonne National Laboratory in Illinois.

 “I have worked at the Advanced Photon Source for over 32 years and I learned many things during this event that I never knew before.  It was quite informative.  I look forward to re-watching the entire event.”

Jeffrey T Collins, Mechanical Engineering & Design Group Leader at Argonne National Laboratory

The symposium began with a historical introduction from Roland Pease, freelance science broadcaster who has been an enthusiastic support of light sources for many years.

Roland’s talk was followed by experts from the field giving talks on their perspectives of synchrotron light related achievements that have been made since the 1st laboratory observation on the 24th April 1947.

Speakers were:

• Nobel Laureate Prof. Ada Yonath (Weizmann Institute of Science)

• Prof. Sir Richard Catlow (University College London)

• Prof. Henry Chapman (DESY)

• Dr Paul Tafforeau (ESRF)

• Dr Gihan Kamel (SESAME and member of the AfLS Executive Committee).

There followed a panel discussion with special guests who all made huge contributions to the development of the field. Our special guests were:

Herman Winick – Prof. of Applied Physics (Research) Emeritus at SLAC)

Ian Munro – Initiator of synchrotron radiation research at Daresbury Laboratory ,Warrington UK in 1970

Giorgio Margaritondo – one of the pioneers in the use of synchrotron radiation and free electron lasers

Gerd Materlik – former CEO of Diamond Light Source, the UK’s synchrotron science facility

Lightsources.org is hugely grateful to all the speakers, special guests and attendees who contributed to this event and made it such a special anniversary celebration for the light source community.

If you have any feedback or memories to share, please do contact Silvana Westbury, Project Manager, at webmaster@lightsources.org

For news, jobs, events and proposal deadlines, please visit the homepage

Science’s great strength is the universal language

Science’s great strength is the universal language

SSRL’s #LightSourceSelfie

Forrest Hyler is a PhD student at the University of California Davis and regular user of the Stanford Synchrotron Lightsource (SSRL). Forrest’s research involves exploring the structural and electronic properties of materials that are used as catalysts for carbon dioxide reduction in the lab. In his #LightSourceSelfie, Forrest describes his work as all encompassing as it involves studying materials related to a broad range of applications such as batteries, catalysis and the storage of radioactive materials. Forrest’s journey has involved a large range of scientists and he says, “The greatest part about science is that it’s kind of that universal language. You get to interact with people around the globe working together for a common goal to push science beyond the boundaries that we’ve ever been at before.”

Developing new alloys for hydrogen fuel and catalysis

Developing new alloys for hydrogen fuel and catalysis

An alloy is a metal that contains two or three different elements. Steel, for instance, is an alloy of iron and carbon that offers increased strength as a building material.

By mixing more elements together, scientists hope to create new and improved alloys with increased strength and improved corrosion resistance, which could help many industry sectors to reduce costs.

“The trouble is that when you try to make a traditional alloy with more than a couple of elements, the elements tend to separate from each other and clump together,” said David Morris, a PhD student in the Department of Chemistry at the Dalhousie University.

That’s why his research team is interested in alloys with five or more elements that have a highly disordered nature. This chaotic property causes the elements to disperse throughout the mixture and prevent clumping. “You can get alloys with elements that wouldn’t usually go together,” he said.

Morris and his colleagues, including Liangbing Hu’s group from the University of Maryland who synthesized the samples using a special carbothermal shock method, are investigating two alloy samples, one made of five elements and another with fifteen.

“Early experiments suggested that the five-element alloy has high catalytic activity for ammonia decomposition, a process used to make hydrogen fuel, but they potentially have all kinds of applications,” he said.

The team gathered data at the Advanced Photon Source (APS) in Illinois, thanks to the facility’s partnership with the Canadian Light Source (CLS) at the University of Saskatchewan. Using synchrotron light, Morris could analyze each element in their samples separately and spot the differences in the structures of the two alloys.

The researchers discovered that the fifteen-element alloy had some elements that showed oxidation and the length of some of the bonds between them increased. These properties, however, were not found in the five-element alloy, indicating the properties of these special alloys are highly dependent on their compositions.

“Increased oxidation means they are less stable, which could potentially increase the activity for catalysis,” said Morris. “And unusual bond lengths can change the properties and maybe make a more promising catalytic pathway.”

The group’s next step will be to try and link the changes in structure seen in this experiment to the alloys’ catalytic activity. “If we are able to find certain structural properties that are associated with a high catalytic activity, that would allow us to design more effective catalysts in the future,” said Morris.

Read more on the CLS website

Image: APS

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Recently, transition-metal dichalcogenides hosting topological states have attracted considerable attention for their potential implications for catalysis and nanoelectronics. The investigation of their chemical reactivity and ambient stability of these materials is crucial in order to assess the suitability of technology transfer. With this aim, an international team of researchers from Italy, Russia, China, USA, India, and Taiwan has studied physicochemical properties of NiTe2 by means of several experimental techniques and density functional theory. Surface chemical reactivity and ambient stability were followed by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) experiments at the BACH beamline, while the electronic band structure was probed by spin- and angle-resolved photoelectron spectroscopy (spin-ARPES) at the APE-LE beamline. 

Read more on the Elettra website

Image: a) Ni-3p core-level spectra collected from as-cleaved NiTe2 (black curves) and from the same surface exposed to 2·104 L of CO (red curves), H2O (green curves) and O2 (blue curves).  Credit: Adapted from “S. Nappini et al., Adv. Funct. Mater. 30, 2000915 (2020); DOI: 10.1002/adfm.202000915” with permission from Wiley (Copyright 2020) with license 4873681106527