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.

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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.

Unraveling the structural transformation of Li-rich materials in lithium-batteries

Lithium-Ion Batteries (LIBs) are essentials in everyday life in mobile applications as well as in hybrid/electric mobility. The extraordinary market success of this technology is forcing hard the need of LIBs with improved energy density, environmental compatibility and safety, making necessary to push this technology beyond the current state of the art. In this framework, Co-poor Lithium Rich Layered Oxides (LRLOs) are the most strategic alternative to current Co-rich layered oxide positive electrode materials thanks to the excellent combination of large specific capacity (>250 mAhg-1), high energy density (up to 900 WhKg-1), small costs and improved environmental benignity. The excellent performance of LRLOs derives from the peculiar combination of redox processes originated from the transition metals and the oxygen anions sublattice. The practical use of LRLOs is hindered by several drawbacks, such as voltage decay, capacity fading, and an irreversible capacity lost in the first cycle. These issues are related to structural rearrangements in the lattice upon cycling.

In this work, we demonstrate a new family of LRLOs with general formula Li1.2+xMn0.54Ni0.13Cox-yAl0.03O2 (0.03 ≤ x ≤ 0.08 and 0.03 ≤ y ≤ 0.05), obtained from the replacement of cobalt with lithium and aluminum and we highlight how the balancing of the metal blend can lead to improvements of the Coulombic efficiency in the first cycle, a better capacity retention and reduced voltage decay. To shed light on the complex crystal-chemistry of this class of LRLOs we studied the Co-poorest member of this homologue material series, namely Li1.28Mn0.54Ni0.13Co0.02Al0.03O2, in order to prove the structural evolution occurring upon charge/discharge in lithium cell. To these aims, electrodes have been recovered during the first cycle, the second cycle and after ten cycles of charge/discharge by de-assembling lithium cells into an Ar-filled glove box. These post mortem materials have been sealed in borosilicate capillary tubes (see Fig. 1a) and studied ex situ by X-ray powder diffraction at the MCX beamline.

Read more on the Elettra website

Image: Fig. 1b shows the potential curves vs time for the first two cycles and highlights the points, marked with A, B, C and so on, where the charge or discharge step was stopped and the materials recovered for analysis. According to the diffraction data (Fig. 1c), structural alterations of Li1.28Mn0.54Ni0.13Co0.02Al0.03O2 start with a fast broadening and a shift of the peaks suggesting a smooth lattice modification. When the cell reaches 4.8V vs Li+, a second phase can be identified. In the discharge process opposite structural transformations occur.

#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

Enigmatic Dirac fermions in graphene

Since the discovery of graphene more than 15 years ago, research on graphene-based systems has grown exponentially. Graphene exhibits unique physical properties, for instance, the presence of massless Dirac fermions in a lattice of stronger covalent bonds and frequency-independent optical conductivity, which may help to realize exotic fundamental science and advanced technologies.

So far, graphene has been grown on a multitude of substrates exhibiting interesting properties. In some cases, the graphene layer has minimal link with the substrate. Experiments have revealed enigmatic properties of the Dirac fermions near the band crossing, called Dirac point, at the K point of the Brillouin zone. For example, Angle-Resolved PhotoEmission Spectroscopy (ARPES) data of graphene grown on SiC, shown in Fig. 1a, exhibit large momentum independent intensities near Dirac point as if the top and bottom of the Dirac cone are shifted away from each other. Some studies interpreted these results as a gapped Dirac cone with anomalous in-gap intensities as schematically shown in Fig. 1b. The presence of electron correlation renormalizes the dispersion as shown by red lines. Other proposals involve plasmaron bands where plasmon excitations in addition to photoexcitation of electrons leads to a shifted Dirac cone. The shifted and the pristine Dirac cones appear as a diamond shaped structure around the Dirac point as shown in Fig. 1c.

In order to address this enigmatic scenario, A. Pramanik, S. Thakur and colleagues from India, Italy and Germany performed a detailed polarization dependent ARPES investigation at the BaDElPh beamline at Elettra. Each branch of the Dirac cone was probed selectively using s– and p-polarized synchrotron light. The spectra shown in Fig. 2a,b reveal clearly dispersive bands near the Dirac point.

Read more on the Elettra website

Image: (a) Typical ARPES spectra of graphene on SiC along the ΓKM direction of the Brillouin zone; the origin of the momentum axis is shifted to K point. Schematic of (b) anomalous region and (c) plasmaron scenario around the Dirac point. Red curved lines in (b) show bands in the presence of electron correlation. Red Dirac cone in (c) is due to plasmaron bands.

Giorgio Margaritondo’s #My1stLight

Synchrotron Radiation from a Synchrotron

We must face reality: almost all synchrotron radiation users of today have never seen a synchrotron! As we know, what they call “synchrotrons” are really “storage rings”. Only a tiny minority of elderly, retired scientists worked at real synchrotrons – and were lucky to survive the experience. I am one of them. Indeed, the first time I used synchrotron radiation was in the 1970s at the 1.1 GeV “elettrosincrotrone” of the Frascati National Laboratory. Which in the 1970s was the source for our synchrotron radiation project “PULS”.

How was my experience? Miserable! Contrary to a storage ring, a synchrotron is a pulsed source in which electron bunches are continuously injected, accelerated and dumped. The bunches cause very dangerous radiation, so we could not work close to our experimental chamber when they travelled in the ring. This transformed simple operations into a nightmare. For example, a sample alignment that takes a few minutes at a storage ring required days or weeks — subsequent small adjustments being separated by hours of accelerator operation.

At Frascati, we were dreaming of using the excellent storage ring Adone instead of the synchrotron — but this happened only later. Personally, after months of misery I found a way out when I was hired by Bell Labs in New Jersey. Which, to my relief, was as far as possible from the synchrotron facilities of that time. But I could not escape my destiny: shortly after my arrival, Bell Labs asked me to start experiments at the Wisconsin Synchrotron Radiation Center! Fortunately, the source there was not a synchrotron but the storage ring Tantalus. I could thus appreciate the huge advantage over real synchrotrons. I am indeed convinced from experience that, without the arrival of storage rings, synchrotron radiation research would have died at birth.

Giorgio Margaritondo
Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne
(EPFL), CH-1020 Lausanne, Switzerland

Image: The Frascati electron synchrotron, where my career in synchrotron radiation started and almost
ended

Great minds think alike!

Marion Flatken from BESSY II & Luisa Napolitano from Elettra give advice to those at the start of their careers

Our #LightSourceSelfies campaign features staff and users from 25 light sources across the world. We invited them all to answer a specific set of questions so we could share their insights and advice via this video campaign. Today’s montage features Marion Flatken from BESSY II, in Germany, and Luisa Napolitano from Elettra, in Italy. Both scientists offered the same advice to those starting out on their scientific journeys: “Be curious and stay curious”. Light source experiments can be very challenging and the tough days can lead to demotivation and self-doubts. In these times, it is good to seek out support from colleagues, all of whom will have experienced days like this. Even if you think you can’t succeed with your research goals, try because it is amazing what can be achieved through hard work, tenacity and collaboration.

Be curious and stay curious!

Luisa Napolitano is a staff scientist working in the structural biology lab at the Elettra Sincrotrone in Trieste, Italy.

In her #LightSourceSelfie, Luisa talks about switching from cellular biology to structural biology and how proud moments come when you solve a structure that you have been working on for years.

Her fantastic lab tour explains how the equipment enables you to prepare proteins for a range of experimental techniques, including crystallography, electron microscopy, SAXS and NMR. Luisa also explains why it is so valuable to have a structural biology lab located at the synchrotron where beamline staff are on hand to give you advice about your research.

Finally Luisa touches on the way her work as a scientist is helping to inspire her 9 year old son. She offers this advice to younger peers, “Be curious and stay curious! Don’t be afraid and try, even if you think something is too much for you. Try it because you never know. It was like me when I started in structural biology at the beginning, I was scared but at the end of the story I like structural biology a lot, and I don’t think I will change my field of action anymore.”

Observation of Magnetoelectric Coupling

Multiferroic materials with coexisting ferroelectric and ferromagnetic orders have attracted much attention due to the magnetoelectric (ME) coupling opening prospects for alternative multifunctional electronic devices.  Switching magnetization by applied electric rather than magnetic field or spin-polarized current requires much less energy, making multiferroics promising for memory and logic applications. Due to a limited number of single-phase multiferroic compounds operating at room temperature, composite multiferroics containing ferroelectric and ferromagnetic components have been considered as viable alternatives. Moreover, it was shown that composite multiferroic materials often have much larger magnetoelectric coupling effect compared to their single-phase counterparts.

The recently emerged class of polycrystalline doped HfO2-based ferroelectric thin films, which are compatible with the modern Si technology, is a promising ferroelectric component in composite multiferroic heterostructures and it is therefore crucial to explore the ME effect at the ferroelectric/ferromagnetic interface in the heterostructures comprising doped HfO2. In this respect, a strong charge-mediated magnetoelectric coupling at the interface between classical ferromagnetic metal – Ni and ferroelectric HfO2has been recently predicted by theoretical modelling.

Read more on the Elettra Website

Image: Schematic drawing of a single capacitor device structure used in operando XAS/XMCD and HAXPES/MCDAD measurements with EELS (Electron energy loss spectroscopy) map of Co, Ni and O. Polarization vs. voltage hysteresis loop at RT and LT (left) and  MOKE (right) of Au/Co/Ni/HZO/W sample are also shown in figure.

Credit: Elettra

Activation of order-disorder dynamics in crystalline Buckybowls

Dibenzo[ghi,mno]Fluoranthene, akacorannulene (C20H10), is a peculiar bowl-shaped molecule displaying unusual pentagonal symmetry and building block of the most celebrated Buckminster Fullerene – C60


Its nanostructured arrangement together with the eminent dipole moment of 2.1 Debye and a high electron affinity, make this system largely appealing for its use in energy-related applications, such as in hydrogen storage, ion-batteries, or super-capacitors. Additionally, this molecule has been suggested to be a component of interstellar dusts.   
In this work, published in Carbon, an international group including researchers from Italy, United Kingdom, Spain, and China has brought to the fore the unexpectedly rich thermophysical behaviour of this system in the thermal range 200 – 600 K, not anticipated on the basis of previous studies.


Combining state-of-the-art synchrotron (MCX beamline, Elettra) and neutron (IRIS beamline, ISIS) scattering techniques, together with differential scanning calorimetry (DSC), for the first time a well defined pre-melting transition has been clearly identified starting at about 382 K, well below the melting point of 540 K, resulting in the progressive suppression of molecular and supramolecular order and associated to the emergence of rotor-like states, as highlighted by the decrease in the elastic intensity and the sizeable increase in the quasi-elastic scattering (see Fig 1b– showing a marked separation in temperature between the two regimes).  

Read more on the Elettra website

Image: Figure 1.  (a) Synchrotron powder diffraction and Rietveld refinement of the room temperature average structure of Corannulene. (b) Temperature dependent quasi-elastic (IQE) and elastic (Iel) fractions, highlighting the transition to the dynamic state.

Recycling alginate composites for thermal insulation

Thermal insulation materials represent one the most straightforward, yet effective, technologies for improving the energy efficiency of buildings (and not only) – one of the key strategies for reducing carbon emissions. Natural-based materials and downcycled industrial and agricultural waste, thanks to their potentially reduced environmental footprint, have already made their way up to the market with the aim of limiting the ever-growing waste stream generated by the industrial sector. Research efforts on the topic are currently mainly focused on developing new insulation solutions, in which waste is reconverted as a new valuable resource. Carbohydrates, such as alginate, cellulose or chitosanare currently extensively studied base materials for thermal insulation systems, in the form of aerogels or as low-impact binding agents in waste-filled panels. Unfortunately, little or no attention has been paid to the end-of-life fate of these recycled materials; disposal (or incineration) still represents the only available option. This unprofitable scenario is even more critical in the case of polysaccharide-based composites specifically developed to reuse industrial waste. 


This was the starting point of our work, mainly conducted at the laboratories of the Engineering and Architecture department of the University of Trieste, in collaboration with TomoLab at Elettra. We developed a recycling process for an alginate-based thermal insulation foam, in which the original material is fully recovered and the thermal and acoustic insulation performances are maintained. The original foam is produced via a patented process in which alginate is used as the host poly-anionic matrix for industrial fiberglass waste. 

Read more on the Elettra website

Image: SEM and μCT image of oCAF

Credit: Figure reprinted from Carbohydrate Polymers, 251, Matteo Cibinel, Giorgia Pugliese, Davide Porrelli, Lucia Marsich, Vanni Lughi, Recycling alginate composites for thermal insulation, 116995, Copyright 2021, with permission from Elsevier.

Unravelling the molecular structure, self-assembly, and properties of a cephalopod protein variant

Cephalopods, such as the loliginid in Figure 1A, are known for their remarkable ability to rapidly change the color and appearance of their skin. These capabilities are enabled in part by unique structural proteins called reflectins, which play essential roles in optical behavior of cephalopod skin cells. Moreover, reflectins have demonstrated exciting potential as functional materials within the context of biophotonic and bioelectronic systems. Given reflectins’ demonstrated significance from both fundamental biology and applications perspectives, some research effort has been devoted to resolving their three-dimensional (3D) structures. However, the peculiar sequence composition of reflectins has made them extremely sensitive to subtle changes in environmental conditions and prone to aggregation, thus significantly complicating the study of their structure-function relationships and precluding their definitive molecular-level structural characterization. In this work, we have elucidated the structure of a reflectin variant at the molecular level, demonstrated a robust methodology for controlling its assembly and optical properties.


We began our studies by rationally selecting a prototypical reflectin variant (RfA1TV) by using a bioinformatics-guided approach (Figure 1B). Next, we not only produced the variant in high yield and purity but also optimized conditions for maintaining this protein in a monomeric state (Figure 1C). We then probed the protein with small angle X-ray scattering (SAXS) using the Austrian SAXS beamline at the Elettra Synchrotron Laboratory in Trieste, Italy. For this purpose, a well-dispersed solution of RfA1TV was prepared in a low-pH buffer and transferred into a glass capillary, which was positioned in the path of an incident X-ray beam. The X-rays scattered by the solution-borne RfA1TV molecules formed a 2-D pattern on a Pilatus3 1M detector (Figure 1D). Subsequently, radial averaging and image calibration of the two-dimensional data furnished corresponding one-dimensional curves, which were further processed, analyzed, and correlated with other experiments to obtain insight into the protein’s geometry (Figure 1E).

Read more on the Elettra website

Image: (A) A camera image of a Doryteuthis pealeii squid. (B) An illustration of the selection of the prototypical truncated reflectin variant (RfA1TV) from full-length Doryteuthis pealeii reflectin A1. (C) A digital camera image of a solution of primarily monomeric RfA1TV (Upper) and a corresponding cartoon of RfA1TV monomers (Lower Inset). (D) An illustration of the SAXS analysis of the reflectin variant, wherein incident X-rays are scattered by the solution-borne proteins to furnish a corresponding scattering pattern. (E)The 3D structure of RfA1TV (random coils – gray, helices – orange, β-strands – purple). 

Credit: This figure has been adapted from M. J. Umerani*, P. Pratakshya* et al.Proc. Natl. Acad. Sci. U.S.A 117, 32891-32901 (2020).

Unusual reversibility of molecular break-up of PAHs

By combining the high-resolution x-ray photoelectron spectroscopy at the SuperESCA beamline of Elettra with density functional theory a group of scientists from Italy, UK, Denmark and Germany has shown that the process of hydrogen removal from pentacene molecules adsorbed on Ir(111) follows a reversible chemical route, which allows hydrogen re-attachment to the carbon nanoribbon formed after the thermally induced C–H bond break-up. The thermal dissociation taking place upon controlled annealing can be reversed by cooling the system at room temperature and in a hydrogen atmosphere.


Besides the novelty of the chemical process, this phenomenon could have interesting implications for molecular electronics and for the manipulation of graphene nanoribbons which are known to present higher electron/hole mobilities and better thermal transport when dehydrogenated. 

Read more on the Elettra website

The power of surfaces: getting meta-polyaniline from para-aminophenol

Within the relatively young research field of the on-surface Chemistry the catalytic properties of surfaces are used to synthesize new materials that are not accessible with other techniques; in particular, by wet chemistry conventional routes. Following this bottom-up strategy, surfaces can be used as suitable platforms for enabling the emergence of novel low-dimensional molecular networks. In synergistic contribution,para-aminophenol (p-AP) molecules are taken as precursors (building block) for the surface reaction. Within a multi-technique approach that includes STM, nc-AFM, STS, XPS, and DFT calculations, we have found that these molecules, when adsorbed on Pt(111) and upon a thermal stimulus, covalently react each other forming oligomers coupled in an unprecedented metaconfiguration.

STM and nc-AFM microscopies showed that starting from individual molecules and by annealing the surface, results in the formation of oligomer chains , while monitoring the thermal behavior of the p-AP/Pt(111) system by means of high-resolution XPS at the SuperESCA beamline of Elettra shed light on the chemical nature of the species present on the crystal surface in the steps which lead to the synthesis of meta-polyaniline oligomers.

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Disclosing the time evolution of magnetic chirality after an optical excitation

Chiral magnetic structures, such as spin spirals, chiral domain walls and skyrmions, are intensively investigated due to their fascinating properties such as potentially enhanced stability and efficient spin-orbit torque driven dynamics. These structures are stabilized by the Dzyaloshinskii-Moriya interaction (DMI) that favours a chiral winding of the magnetisation.Cir

In a recent work, circularly polarized light pulses of the FERMI free-electron laser (FEL) has been used to disclose the dynamics of chiral order on ps time scale. After an optical excitation, the researchers observe a faster recovery of the chirality within the domain walls compared to the ferromagnetic order in the domains. The study paves the way for future investigations of fundamental aspects such as, e.g., the dependence of the timescales of the chiral order build-up on the absolute strength of the DMI. The control of the DMI can finally allow the manipulation at ultrafast timescale of chiral topological objects such as skyrmions and pave the path to applications in the field of ultrafast chiral spintronics.

Rad more on the Elettra website