Influence of Crystallographic Structure and Metal Vacancies on the Oxygen Evolution Reaction Performance of Ni-based Layered Hydroxides.

Nickel-based layered hydroxides (LHs) are a family of efficient electrocatalysts for the alkaline oxygen evolution reaction (OER). Nevertheless, fundamental aspects such as the influence of the crystalline structure and the role of lattice distortion of the catalytic sites remain poorly understood and typically muddled. Herein, we carried out a comprehensive investigation on ɑ-LH, ß-LH and layered double hydroxide (LDH) phases by means of structural, spectroscopical, in-silico and electrochemical studies, which suggest the key aspect exerted by Ni-vacancies in the ɑ-LH structure. Density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS) confirm that the presence of Ni-vacancies produces acute distortions of the electroactive Ni sites (reflected as the shortening of the Ni-O distances and changes in the O-Ni-O angles), triggering the appearance of Ni localised electronic states on the Fermi level, reducing the Egap, and consequently, increasing the reactivity of the electroactive sites in the ɑ-LH structure. Furthermore, post-mortem Raman and XAS measurements unveil its transformation into a highly reactive oxyhydroxide-like phase that remains stable under ambient conditions. Hence, this work pinpoints the critical role of the crystalline structure as well as the electronic properties of LH structures on their inherent electrochemical reactivity towards OER catalysis. We envision Ni-based ɑ-LH as a perfect platform for hosting trivalent cations, closing the gap toward the next generation of benchmark efficient earth-abundant electrocatalysts.

Structural evolution after oxidative pretreatment and CO oxidation of Au nanoclusters with different ligand shell composition: a view on the Au core.

The reactivity of supported monolayer protected Au nanoclusters is directly affected by their structural dynamics under pretreatment and reaction conditions. The effect of different types of ligands of Au clusters supported on CeO2 on their core structure evolution, under oxidative pretreatment and CO oxidation reaction, was investigated. X-ray absorption and X-ray photoelectron spectroscopy studies revealed that the clusters evolve to a similar core structure above 250 °C in all the cases, indicating the active role of the ligand-support interaction in the reaction.

Investigating the local structure of Ti based MXene materials by temperature dependent X-ray absorption spectroscopy.

The local structures of Ti based MXene-type electrode materials have been studied by Ti K-edge X-ray absorption fine structure measurements as a function of temperature to obtain direct information on the local bond lengths and their stiffness. In particular, the parent MAX phases Ti2AlC and Ti3AlC2 and their etched MXene systems are characterized and their properties compared. We find that selective etching has a substantial effect on the local structural properties of the Ti based MXene materials. It leads to an increase in the interatomic distances, i.e. a decrease in the covalency, and corresponding bond stiffness, that is a likely cause of higher achievable performances. The obtained results underline the importance of the local atomic correlations as limiting factors in the diffusion capacity of ion batteries.

Modulation of the Circulating Extracellular Vesicles in Response to Different Exercise Regimens and Study of Their Inflammatory Effects.

Exercise-released extracellular vesicles (EVs) are emerging as a novel class of exerkines that promotes systemic beneficial effects. However, slight differences in the applied exercise protocols in terms of mode, intensity and duration, as well as the need for standardized protocols for EV isolation, make the comparison of the studies in the literature extremely difficult. This work aims to investigate the EV amount and EV-associated miRNAs released in circulation in response to different physical exercise regimens. Healthy individuals were subjected to different exercise protocols: acute aerobic exercise (AAE) and training (AT), acute maximal aerobic exercise (AMAE) and altitude aerobic training (AAT). We found a tendency for total EVs to increase in the sedentary condition compared to trained participants following AAE. Moreover, the cytofluorimetric analysis showed an increase in CD81+/SGCA+/CD45- EVs in response to AAE. Although a single bout of moderate/maximal exercise did not impact the total EV number, EV-miRNA levels were affected as a result. In detail, EV-associated miR-206, miR-133b and miR-146a were upregulated following AAE, and this trend appeared intensity-dependent. Finally, THP-1 macrophage treatment with exercise-derived EVs induced an increase of the mRNAs encoding for IL-1ß, IL-6 and CD163 using baseline and immediately post-exercise EVs. Still, 1 h post-exercise EVs failed to stimulate a pro-inflammatory program. In conclusion, the reported data provide a better understanding of the release of circulating EVs and their role as mediators of the inflammatory processes associated with exercise.

Rhodium Single-Atom Catalyst Design through Oxide Support Modulation for Selective Gas-Phase Ethylene Hydroformylation.

A frontier challenge in single-atom (SA) catalysis is the design of fully inorganic sites capable of emulating the high reaction selectivity traditionally exclusive of organometallic counterparts in homogeneous catalysis. Modulating the direct coordination environment in SA sites, via the exploitation of the oxide support's surface chemistry, stands as a powerful albeit underexplored strategy. We report that isolated Rh atoms stabilized on oxygen-defective SnO2 uniquely unite excellent TOF with essentially full selectivity in the gas-phase hydroformylation of ethylene, inhibiting the thermodynamically favored olefin hydrogenation. Density Functional Theory calculations and surface characterization suggest that substantial depletion of the catalyst surface in lattice oxygen, energetically facile on SnO2 , is key to unlock a high coordination pliability at the mononuclear Rh centers, leading to an exceptional performance which is on par with that of molecular catalysts in liquid media.

MOF-Stabilized Perfluorinated Palladium Cages Catalyze the Additive-Free Aerobic Oxidation of Aliphatic Alcohols to Acids.

Extremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ-donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine-Pd2+ coordinate cages within the channels of an anionic tridimensional metal-organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF-stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd2+ to dehydrogenate primary alcohols, without any base, and also to activate O2 for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required.

Soluble/MOF-Supported Palladium Single Atoms Catalyze the Ligand-, Additive-, and Solvent-Free Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids.

Metal single-atom catalysts (SACs) promise great rewards in terms of metal atom efficiency. However, the requirement of particular conditions and supports for their synthesis, together with the need of solvents and additives for catalytic implementation, often precludes their use under industrially viable conditions. Here, we show that palladium single atoms are spontaneously formed after dissolving tiny amounts of palladium salts in neat benzyl alcohols, to catalyze their direct aerobic oxidation to benzoic acids without ligands, additives, or solvents. With this result in hand, the gram-scale preparation and stabilization of Pd SACs within the functional channels of a novel methyl-cysteine-based metal-organic framework (MOF) was accomplished, to give a robust and crystalline solid catalyst fully characterized with the help of single-crystal X-ray diffraction (SCXRD). These results illustrate the advantages of metal speciation in ligand-free homogeneous organic reactions and the translation into solid catalysts for potential industrial implementation.

MAP2XANES: a Jupyter interactive notebook for elemental mapping and XANES speciation.

MAP2XANES is an intuitive Jupyter notebook that automatizes the analysis of synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy for the characterization of complex and heterogeneous samples. The notebook uses basic modules and functions from Numpy, Scipy, Pandas, iPywidgets and Matplotlib libraries for a powerful data reduction process that, in just a few clicks, guides the user through the visualization of elemental maps, space-resolved absorption spectra and their automatized analysis. In particular, by means of linear combination fit of the XANES spectra, the notebook determines the chemical species distribution in the sample under investigation. The direct output of the analysis process is the correlation between the different elemental distributions and the spatial localization of the chemical species detected. An application to mineralogy is thus presented, analyzing the Mn2+, Mn3+ and Mn4+ distribution in a mineral sample of hausmannite (Mn2+Mn23+O4), courtesy of the Museum of Natural Science of Barcelona.

Electromechanically active pair dynamics in a Gd-doped ceria single crystal.

Oxygen-defective ceria, e.g. Gd-doped ceria, shows giant electromechanical properties related to a complex local rearrangement of its lattice. Although they are not entirely identified, the electroactive mechanisms arise from cation and oxygen vacancy (VO) pairs (i.e. Ce-VO), and the local structural elastic distortion in their surroundings. Here, we study the geometry and behaviour of Ce-VO pairs in a grain boundary-free bulk Ce0.9Gd0.1O1.95 single crystal under an AC electric field of ca. 11 kV cm-1. The analysis was carried out through X-ray absorption spectroscopy (XAS) techniques at the Ce L-III edge. Using Density Functional Theory (DFT) calculations, we investigated the effects of the strain on density of states and orbitals at the valence band edge. Our research indicates that electrostriction increases at low temperatures. The electromechanical strain has a structural nature and can rise by one order of magnitude, i.e., from 5 × 10-4 at room temperature to 5 × 10-3 at -193 °C, due to an increase in the population of the electrically active pairs. At a constant VO concentration, the material can thus configure heterogeneous pairs and elastic nanodomains that are either mechanically responsive or not.

Gallium- and Iron-Pyoverdine Coordination Compounds Investigated by X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy.

Iron is an essential nutrient for nearly all forms of life, although scarcely available due to its poor solubility in nature and complex formation in higher eukaryotes. Microorganisms have evolved a vast array of strategies to acquire iron, the most common being the production of high-affinity iron chelators, termed siderophores. The opportunistic bacterial pathogen Pseudomonas aeruginosa synthesizes and secretes two siderophores, pyoverdine (PVD) and pyochelin (PCH), characterized by very different structural and functional properties. Due to its chemical similarity with Fe(III), Ga(III) interferes with several iron-dependent biological pathways. Both PVD and PCH bind Fe(III) and Ga(III). However, while the Ga-PCH complex is more effective than Ga(III) in inhibiting P. aeruginosa growth, PVD acts as a Ga(III) scavenger and protects bacteria from Ga(III) toxicity. To gain more insight into the different outcomes of the biological paths observed for the Fe(III) and Ga(III)-siderophore complexes, better knowledge is needed of their coordination geometries that directly influence the metal complexes chemical stability. The valence state and coordination geometry of the Ga-PCH and Fe-PCH complexes has recently been investigated in detail; as for PVD complexes, several NMR structural studies of Ga(III)-PVD are reported in the literature, using Ga(III) as a diamagnetic isosteric substitute for Fe(III). In this work, we applied up-to-date spectroscopic techniques as synchrotron-radiation-induced X-ray photoelectron spectroscopy (SR-XPS) and X-ray absorption fine structure (XAFS) spectroscopy coupled with molecular modeling to describe the electronic structure and coordination chemistry of Fe and Ga coordinative sites in PVD metal complexes. These techniques allowed us to unambiguously determine the oxidation state of the coordinative ions and to gather interesting information about the similarities and differences between the two coordination compounds as induced by the different metal.

Solid and Aqueous Speciation of Yttrium in Passive Remediation Systems of Acid Mine Drainage.

Yttrium belongs to the rare earth elements (REEs) together with lanthanides and scandium. REEs are commonly used in modern technologies, and their limited supply has made it necessary to look for new alternative resources. Acid mine drainage (AMD) is a potential resource since it is moderately enriched in REEs. In fact, in passive remediation systems, which are implemented to minimize the environmental impacts of AMD, REEs are mainly retained in basaluminite, an aluminum hydroxysulfate precipitate. In this study, the solid and liquid speciation and the local structure of yttrium are studied in high-sulfate aqueous solutions, basaluminite standards, and samples from remediation columns using synchrotron-based techniques and molecular modeling. Pair distribution function (PDF) analyses and ab initio molecular dynamics density functional theory models of the yttrium sulfate solution show that the YSO4+ ion pair forms a monodentate inner-sphere complex. Extended X-ray absorption fine structure (EXAFS) and PDF analyses show that Y is retained by basaluminite, forming a monodentate inner-sphere surface complex on the aluminum hydroxide surface. EXAFS of the column samples shows that more than 72% of their signal is represented by the signal of basaluminite with which YSO4+ forms an inner-sphere complex. The atomic view of the REE configuration in AMD environments could facilitate a deeper research of REE recovery from waste generated in AMD remediation systems.

Discontinuously supervised aerobic training vs. physical activity promotion in the self-management of type 2 diabetes in older Italian patients: design and methods of the 'TRIPL-A' randomized controlled trial.

BACKGROUND: Physical activity (PA) has health benefits for people with type 2 diabetes (T2D). Indeed, regular PA is considered an important part of any T2D management plan, yet most patients adopt a sedentary lifestyle. Exercise referral schemes (ERS) have the potential to effectively promote physical activity among T2D patients, and their effectiveness may be enhanced when they are supported by computer-based technologies. The 'TRIPL-A' study (i.e., a TRIal to promote PhysicaL Activity among patients in the young-old age affected by T2D) aims to assess if realizing an innovative ERS, based on a strong partnership among general practitioners, specialist physicians, exercise specialists, and patients, and supported by a web-based application (WBA), can effectively lead sedentary older T2D patients to adopt an active lifestyle. METHODS: A randomized controlled design will be used, and an ERS, supported by a WBA, will be implemented. 300 physically inactive T2D patients (aged 65-74 years) will be assigned to either an intervention or control arm. Control arm patients will only receive behavioral counseling on physical activity and diet, while intervention arm patients will also undergo an 18-month (3 day/week), discontinuously supervised aerobic exercise training program. The trial will be divided into six three-month periods: during first, third and fifth period, an exercise specialist will supervise the training sessions and, using the WBA, prescribe exercise progression and monitor exercise adherence. Patients will exercise on their own in the other periods. Patients' sedentary behaviors (primary outcome), PA level, fitness status, metabolic profile, psychological well-being, quality of life, and use of health care services (secondary outcomes) will be assessed at baseline and at 6, 12, and 18 months from baseline. Repeated measure ANCOVAs will be used to compare the intervention and control arm with respect to each study outcome measure. DISCUSSION: Primary and secondary outcome results will allow us to evaluate the effectiveness of an ERS, specifically designed for the management of T2D clinical conditions and supported by a WBA, in promoting PA within Italian primary care settings. TRIAL REGISTRATION: This trial is retrospectively registered under the Australian New Zealand Clinical Trials Registry (reference number: ACTRN12618001164280 ; registered 13 July 2018).

Selenite Uptake by Ca-Al LDH: A Description of Intercalated Anion Coordination Geometries.

Layered double hydroxides (LDHs) are anion exchangers with a strong potential to scavenge anionic contaminants in aquatic environments. Here, the uptake of selenite (SeO32-) by Ca-Al LDHs was investigated as a function of Se concentration. Thermodynamic modeling of batch sorption isotherms shows that the formation of SeO32--intercalated AFm (hydrated calcium aluminate monosubstituent) phase, AFm-SeO3, is the dominant mechanism controlling the retention of Se at medium loadings. AFm-Cl2 shows much stronger affinity and larger distribution ratio (Rd ∼ 17800 L kg-1) toward SeO32- than AFm-SO4 (Rd ∼ 705 L kg-1). At stoichiometric SeO32- loading for anion exchange, the newly formed AFm-SeO3 phase results in two basal spacing, i.e., 9.93 ± 0.06 Å and ∼11.03 ± 0.03 Å. Extended X-ray absorption fine structure (EXAFS) spectra indicate that the intercalated SeO32- forms inner-sphere complexes with the Ca-Al-O layers. In situ X-ray diffraction (XRD) shows that basal spacing of Ca-Al LDHs have a remarkable linear relationship with the size of hydrated intercalated anions (i.e., Cl-, SO42-, MoO42-, and SeO32-). Contrary to AFm-SeO3 with inner-sphere SeO32- complexes in the interlayer, the phase with hydrogen-bonded inner-sphere complexed SeO32- is kinetically favored but thermodynamically unstable. This work offers new insights about the determination of intercalated anion coordination geometries via XRD analyses.

Effects of nanostructuring on the bond strength and disorder in V2O5 cathode material for rechargeable ion-batteries.

We have investigated the nanostructuring effects on the local structure of V2O5 cathode material by means of temperature dependent V K-edge X-ray absorption fine structure measurements. We have found that the nanostructuring largely affects V-O and V-V bond characteristics with a general softening of the local V-O and V-V bonds. The obtained bond strengths correlate with the specific capacity shown by the different systems, with higher capacity corresponding to softer atomic pairs. The present study suggests the key role of local atomic displacements in the diffusion and storage of ions in cathodes for batteries, providing important information for designing new functional materials.

Melting of iron determined by X-ray absorption spectroscopy to 100 GPa.

Temperature, thermal history, and dynamics of Earth rely critically on the knowledge of the melting temperature of iron at the pressure conditions of the inner core boundary (ICB) where the geotherm crosses the melting curve. The literature on this subject is overwhelming, and no consensus has been reached, with a very large disagreement of the order of 2,000 K for the ICB temperature. Here we report new data on the melting temperature of iron in a laser-heated diamond anvil cell to 103 GPa obtained by X-ray absorption spectroscopy, a technique rarely used at such conditions. The modifications of the onset of the absorption spectra are used as a reliable melting criterion regardless of the solid phase from which the solid to liquid transition takes place. Our results show a melting temperature of iron in agreement with most previous studies up to 100 GPa, namely of 3,090 K at 103 GPa.

Evidence of Multiple Sorption Modes in Layered Double Hydroxides Using Mo As Structural Probe.

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO42-) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO4 precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms-edge sorption, interfacial dissolution-reprecipitation-are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.

A new detector for sub-millisecond EXAFS spectroscopy at the European Synchrotron Radiation Facility.

A new FReLoN (Fast-Readout Low-Noise) high-frame-rate detector adopted for the fast continuous collection of X-ray absorption spectra is presented. The detector is installed on the energy-dispersive X-ray absorption beamline ID24 at the ESRF and is capable of full time-resolved EXAFS spectra collection with over 4 kHz repetition rate and 0.2 ms exposure time. An example of the in situ kinetic study of the high-temperature oxidation of metallic iron is presented.

Copper single-site engineering in MOF-808 membranes for improved water treatment.

MOF-808, a metal-organic framework containing Zr6O8 clusters, can serve as a secure anchoring point for stabilizing copper single-sites with redox activity, thus making it a promising candidate for catalytic applications. In this study, we target the incorporation of Cu-MOF-808 into a mixed-matrix membrane for the degradation of tyrosol, an emerging endocrine-disrupting compound commonly found in water sources, through Fenton reactions, developing innovative technologies for water treatment. We successfully demonstrate the effectiveness of this approach by preparing catalytic membranes with minimal metal leaching, which is one of the primary challenges in developing copper-based Fenton heterogeneous catalysts. Furthermore, we utilized advanced synchrotron characterization techniques, combining X-ray absorption spectroscopy and pair distribution function analysis of X-ray total scattering, to provide evidence of the atomic structure of the catalytic copper sites within the membranes. Additionally, we observed the presence of weak interactions between the MOF-808 and the organic polymer, potentially explaining their enhanced stability.

Are incremental exercise relationships between rating of perceived exertion and oxygen uptake or heart rate reserve valid during steady-state exercises?

Background: Rating of perceived exertion (RPE) is considered a valid method for prescribing prolonged aerobic steady-state exercise (SSE) intensity due to its association with physiological indicators of exercise intensity, such as oxygen uptake (V̇O2) or heart rate (HR). However, these associations between psychological and physiological indicators of exercise intensity were found during graded exercise tests (GXT) but are currently used to prescribe SSE intensity even though the transferability and validity of the relationships found during GXT to SSE were not investigated. The present study aims to verify whether (a) RPE-HR or RPE-V̇O2 relations found during GXTs are valid during SSEs, and (b) the duration and intensity of SSE affect these relations. Methods: Eight healthy and physically active males (age 22.6 ± 1.2 years) were enrolled. On the first visit, pre-exercise (during 20 min standing) and maximal (during a GXT) HR and V̇O2 values were measured. Then, on separate days, participants performed 4 SSEs on the treadmill by running at 60% and 80% of the HR reserve (HRR) for 15 and 45 min (random order). Individual linear regressions between GXTs' RPE (dependent variable) and HRR and V̇O2 reserve (V̇O2R) values (computed as the difference between maximal and pre-exercise values) were used to predict the RPE associated with %HRR (RPEHRR) and %V̇O2R (RPEV̇O2R) during the SSEs. For each relation (RPE-%HRR and RPE-%V̇O2R), a three-way factorial repeated measures ANOVA (α = 0.05) was used to assess if RPE (dependent variable) was affected by exercise modality (i.e., RPE recorded during SSE [RPESSE] or GXT-predicted), duration (i.e., 15 or 45 min), and intensity (i.e., 60% or 80% of HRR). Results: The differences between RPESSE and GXT-predicted RPE, which were assessed by evaluating the effect of modality and its interactions with SSE intensity and duration, showed no significant differences between RPESSE and RPEHRR. However, when RPESSE was compared with RPEV̇O2R, although modality or its interactions with intensity were not significant, there was a significant (p = 0.020) interaction effect of modality and duration yielding a dissociation between changes of RPESSE and RPEV̇O2R over time. Indeed, RPESSE did not change significantly (p = 0.054) from SSE of 15 min (12.1 ± 2.0) to SSE of 45 min (13.5 ± 2.1), with a mean change of 1.4 ± 1.8, whereas RPEV̇O2R decreased significantly (p = 0.022) from SSE of 15 min (13.7 ± 3.2) to SSE of 45 min (12.4 ± 2.8), with a mean change of -1.3 ± 1.5. Conclusion: The transferability of the individual relationships between RPE and physiological parameters found during GXT to SSE should not be assumed as shown by the results of this study. Therefore, future studies modelling how the exercise prescription method used (e.g., RPE, HR, or V̇O2) and SSE characteristics (e.g., exercise intensity, duration, or modality) affect the relationships between RPE and physiological parameters are warranted.

Ni-Ru supported on CeO2 obtained by mechanochemical milling for catalytic hydrogen production from ammonia.

Developing active and stable catalysts for carbon-free hydrogen production is crucial to mitigate the effects of climate change. Ammonia is a promising carbon-free hydrogen source, as it has a high hydrogen content and is liquid at low pressure, which allows its easy storage and transportation. We have recently developed a nickel-based catalyst with a small content of ruthenium supported on cerium oxide, which exhibits high activity and stability in ammonia decomposition. Here, we investigate mechanochemical milling for its synthesis, a faster and less energy-consuming technique than conventional ones. Results indicate that mechanochemical synthesis increases catalytic activity compared to the conventional incipient wetness impregnation method. The interaction between the metal precursors and the support is key in fine-tuning catalytic activity, which increases linearly with oxygen vacancies in the support. Moreover, the mechanochemical method modifies the oxidation state of Ni and Ru species, with a variation depending on the precursors.