Are Operando Measurements of Rechargeable Batteries Always Reliable? An Example of Beam Effect with a Mg Battery.

Operando and in situ techniques are becoming mandatory to study Li-ion, post Li-ion, and solid-state batteries. They are essential for monitoring the (electro)chemical and dynamic processes in the battery environment and for providing understanding at different spatial and temporal scales. While operando measurements are becoming more and more routine, scientists have to keep in mind that such experiments are not always harmless for the battery operation, especially when using synchrotron techniques. This is the case in the example described herein with Mg batteries. We show that the electrode reactivity in a InSb/organohaluminate electrolyte/Mg cell is strongly retarded during operando synchrotron X-ray absorption acquisition. Through comparison of ex situ, operando, and in situ data, we demonstrate that this effect occurred only on the samples' volumes exposed to the X-ray radiation. This study illustrates how incorrect conclusions might be drawn from operando measurements, especially when looking at new battery chemistries, and calls for extreme caution when designing and interpreting operando data.

Detecting recent forgeries of Impressionist and Pointillist paintings with high-precision radiocarbon dating.

We report on the capacity of AMS radiocarbon dating to play a decisive role in fighting against the illicit trade in art. In the framework of a current police investigation, where previously unseen paintings were discovered in a restorer's workshop by the French Central Office for the Fight against Illicit Trafficking in Cultural Property (OCBC), we demonstrated that two paintings alleged to be by Impressionist and Pointillist artists had in fact been painted recently. Our results were based on the excess of 14C derived from atmospheric nuclear tests detected in the fibers used to make the canvas. By combining AMS 14C absolute dating and the fine precision of the post-bomb atmospheric calibration curve, we established a clear chronological context for the production of these forgeries. 14C content of the fibers revealed that the canvases were manufactured in 1956-1957 or, more likely, after 2000. As a result, absolute dating proves unambiguously that the Impressionist and Pointillist paintings are forgeries since they were not painted at the beginning of the 20th century by the alleged artists, who died in the 1940s.

MIL-53 Metal-Organic Framework as a Flexible Cathode for Lithium-Oxygen Batteries.

Li-air batteries possess higher specific energies than the current Li-ion batteries. Major drawbacks of the air cathode include the sluggish kinetics of the oxygen reduction (OER), high overpotentials and pore clogging during discharge processes. Metal-Organic Frameworks (MOFs) appear as promising materials because of their high surface areas, tailorable pore sizes and catalytic centers. In this work, we propose to use, for the first time, aluminum terephthalate (well known as MIL-53) as a flexible air cathode for Li-O2 batteries. This compound was synthetized through hydrothermal and microwave-assisted routes, leading to different particle sizes with different aspect ratios. The electrochemical properties of both materials seem to be equivalent. Several behaviors are observed depending on the initial value of the first discharge capacity. When the first discharge capacity is higher, no OER occurs, leading to a fast decrease in the capacity during cycling. The nature and the morphology of the discharge products are investigated using ex situ analysis (XRD, SEM and XPS). For both MIL-53 materials, lithium peroxide Li2O2 is found as the main discharge product. A morphological evolution of the Li2O2 particles occurs upon cycling (stacked thin plates, toroids or pseudo-spheres).

Operando NMR characterization of a metal-air battery using a double-compartment cell design.

Applying operando investigations is becoming essential for acquiring fundamental insights into the reaction mechanisms and phenomena at stake in batteries currently under development. The capability of a real-time characterization of the charge/discharge electrochemical pathways and the reactivity of the electrolyte is critical to decipher the underlying chemistries and improve the battery performance. Yet, adapting operando techniques for new chemistries such as metal-oxygen (i.e. metal-air) batteries introduces challenges in the cell design due notably to the requirements of an oxygen gas supply at the cathode. Herein a simple operando cell is presented with a two-compartment cylindrical cell design for NMR spectroscopy. The design is discussed and evaluated. Operando7Li static NMR characterization on a Li-O2 battery was performed as a proof-of-concept. The productions of Li2O2, mossy Li/Li dendrites and other irreversible parasitic lithium compounds were captured in the charge/discharge processes, demonstrating the capability of tracking the evolution of the anodic and cathodic chemistry in metal-oxygen batteries.

One-Step Synthesis of TiO2/Graphene Nanocomposites by Laser Pyrolysis with Well-Controlled Properties and Application in Perovskite Solar Cells.

This work presents an original synthesis of TiO2/graphene nanocomposites using laser pyrolysis for the demonstration of efficient and improved perovskite solar cells. This is a one-step and continuous process known for nanoparticle production, and it enables here the elaboration of TiO2 nanoparticles with controlled properties (stoichiometry, morphology, and crystallinity) directly grown on graphene materials. Using this process, a high quality of the TiO2/graphene interface is achieved, leading to an intimate electronic contact between the two materials. This effect is exploited for the photovoltaic application, where TiO2/graphene is used as an electron-extracting layer in n-i-p mesoscopic perovskite solar cells based on the reference CH3NH3PbI3-x Cl x halide perovskite active layer. A significant and reproducible improvement of power conversion efficiencies under standard illumination is demonstrated, reaching 15.3% in average compared to 13.8% with a pure TiO2 electrode, mainly due to a drastic improvement in fill factor. This beneficial effect of graphene incorporation is revealed through pronounced photoluminescence quenching in the presence of graphene, which indicates better electron injection from the perovskite active layer. Considering that a reduction of device hysteresis is also observed by graphene addition, the laser pyrolysis technique, which is compatible with large-scale industrial developments, is therefore a powerful tool for the production of efficient optoelectronic devices based on a broad range of carbon nano-objects.

Impacts of one century of wastewater discharge on soil transformation through ferrolysis and related metal pollutant distributions.

Discharge of wastewater leading to notable soil surface contamination is widely reported. But few works highlight the fast dynamics of soils and their morphological transformations that may result from such anthropogenic activities. Near Paris (France), sandy Luvisols were irrigated with urban wastewater since the 1890s. Within and outside the discharge area, the soil cover presents decameter-sized cryogenic structures. We studied macro morphological soil characteristics, soil chemistry and clay mineralogy on selected bulk samples, as well as contemporary pedofeatures and related metal pollutant distribution patterns in soil thin sections from subsurface horizons. Annual repetitive waterlogging and drying cycles initiated a hydromorphic soil forming process: ferrolysis, based on iron reduction producing alkalinity under anaerobic conditions, and iron oxidation producing acidity in aerobic conditions. Its intensity was enhanced at the top of thick clay-rich B-horizons in the center of cryogenic structures. The polygonal soil structure favored the evacuating of soil water and alkalinity. Within one century, such recurrent alternating redox conditions have led to clay destruction, removal of iron, strong bleaching of the E horizon and formation of abiotic Fe-rich pedofeatures at depth. In addition, between anaerobic clay-rich B and aerated E or C horizons, the contrasting hydrodynamic conditions enhanced manganese (Mn) oxidizing fungal activity and the formation of biotic Mn-rich pedofeatures. Both types of pedofeatures trapped metal pollutants in deep soil horizons. In our work, the impacts of centenary anthropogenic activity were amplified by millenary cryogenic structures, acting together to promote fast soil dynamics, within a few decades.

Silicon sheets by redox assisted chemical exfoliation.

In this paper, we report the direct chemical synthesis of silicon sheets in gram-scale quantities by chemical exfoliation of pre-processed calcium disilicide (CaSi2). We have used a combination of x-ray photoelectron spectroscopy, transmission electron microscopy and energy-dispersive x-ray spectroscopy to characterize the obtained silicon sheets. We found that the clean and crystalline silicon sheets show a two-dimensional hexagonal graphitic structure.

Combining µX-ray fluorescence, µXANES and µXRD to shed light on Zn2+ cations in cartilage and meniscus calcifications.

We aimed to examine the presence of Zn, a trace element, in osteoarthritis (OA) cartilage and meniscus from patients undergoing total knee joint replacement for primary OA. We mapped Ca(2+) and Zn(2+) at the mesoscopic scale by X-ray fluorescence microanalysis (µX-ray) to determine the spatial distribution of the 2 elements in cartilage, µX-ray absorption near edge structure spectroscopy to identify the Zn species, and µX-ray diffraction to determine the chemical nature of the calcification. Fourier transform infrared spectroscopy was used to determine the chemical composition of cartilage and meniscus. Ca(2+) showed a heterogeneous spatial distribution corresponding to the calcifications within cartilage (or meniscus) or at their surface. At least 2 Zn(2+) species were present: the first may correspond to Zn embedded in protein (different Zn metalloproteins are known to prevent calcification in biological tissues), and the second may be associated with a Zn trap in or at the surface of the calcification. Calcification present in OA cartilage may significantly modify the spatial distribution of Zn; part of the Zn may be trapped in the calcification and may alter the associated biological function of Zn metalloproteins.

High Zn content of Randall's plaque: a µ-X-ray fluorescence investigation.

Kidney stone disease, or nephrolithiasis, is a common ailment. Among the different risk factors usually associated with nephrolithiasis are dehydration, metabolic defects (especially with regard to calcium and oxalate). The presence of a mineral deposit at the surface of the renal papilla (termed Randall's plaque) has all been recently underlined. Of note, Randall's plaque is made of the calcium phosphate, carbapatite, and serves as a nucleus for kidney stone formation. The process by which apatite nanocrystals nucleate and form Randall's plaque remains unclear. This paper deals with the possible relationship between trace elements and the formation of this mineral. The investigation has been performed on a set of Randall's plaques, extracted from human kidney stones, through µ-X-ray diffraction and µ-X-ray fluorescence analyses in order to determine the chemical composition of the plaque as well as the nature and the amount of trace elements. Our data provide evidence that Zn levels are dramatically increased in carbapatite of RP by comparison to carbapatite in kidney stones, suggesting that calcified deposits within the medullar interstitium are a pathological process involving a tissue reaction. Further studies, perhaps including the investigation of biomarkers for inflammation, are necessary for clarifying the role of Zn in Randall's plaque formation.

Anodic activation of iron corrosion in clay media under water-saturated conditions at 90 degrees C: characterization of the corrosion interface.

To understand the process governing iron corrosion in clay over centuries, the chemical and mineralogical properties of solids formed by free or anodically activated corrosion of iron in water-saturated clay at 90 degrees C over 4 months were probed using microscopic and spectroscopic techniques. Free corrosion led to the formation of an internal discontinuous thin (<3 microm thick) magnetite layer, an external layer of Fe-rich phyllosilicate, and a clay transformation layer containing Ca-doped siderite (Ca(0.2)Fe(0.8)CO(3)). The thickness of corroded iron equaled approximately 5-7 microm, consistent with previous studies. Anodic polarization resulted in unequally distributed corrosion, with some areas corrosion-free and others heavily corroded. Activated corrosion led to the formation of an inner magnetite layer, an intermediate Fe(2)CO(3)(OH)(2) (chukanovite) layer, an outer layer of Fe-rich 7 A-phyllosilicate, and a transformed matrix layer containing siderite (FeCO(3)). The corroded thickness was estimated to 85 microm, less than 30% of the value expected from the supplied anodic charge. The difference was accounted for by reoxidation at the anodically polarized surface of cathodically produced H(2)(g). Thus, free or anodically activated corroding conditions led to structurally similar interfaces, indicating that anodic polarization can be used to probe the long-term corrosion of iron in clay. Finally, corrosion products retained only half of Fe oxidized by anodic activation. Missing Fe probably migrated in the clay, where it could interact with radionuclides released by alteration of nuclear glass.

Fate of metal-associated POM in a soil under arable land use contaminated by metallurgical fallout in northern France.

Organic matter is a major metal-retaining constituent in soils. Among the diversity of organic components in soils, particulate organic matter (POM) accumulates large amounts of metals, but the fate of such metal-associated POM is unknown. We studied different POM size fractions and their corresponding mineral size-fractions isolated from the surface horizon of a soil affected by metallurgical fallout. Analyses of total and EDTA extractible metal contents performed on all size fractions demonstrated that with decreasing POM size, larger metal concentrations were observed but they were less extractable. Micromorphological study revealed the occurrence of opaque parts in decaying POM fragments and their individualization as fine, irregularly shaped opaque fragments in the soil matrix. This work suggested a mutual sequestration of metal pollutants and organic carbon as micro-meter sized, metal-enriched organic particles derived from POM, representing an original pathway for natural attenuation of risk related to metal contaminated soils.