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A Colon or ileum number of crypts at 5 days (n = 7-8); percentage of goblet cells along with representative photos of colon and ileum samples, stained by Alcian blue or PAS. * p -value < 0.05; ** p -value < 0.01 Reference 1 Barone M, Ramayo-Caldas Y, Estellé J. Gut barrier-microbiota imbalances in early life lead to higher sensitivity to inflammation in a murine model of C-section delivery. [Extracted from the article]

Abstract: It is usually believed that carbon‐supported electrocatalysts are stable in alkaline environment, owing to the better thermodynamics stability of many metals and oxides at high pH. By focusing on a selected literature review concerning Pt/C and Pd/C nanoparticles, and in particular from identical‐location transmission electron microscopy (ILTEM), it is demonstrated that this “common knowledge” is erroneous in aqueous alkaline electrolytes: both Pt/C and Pd/C suffer pronounced loss of electrochemical surface area (ECSA), and the latter is linked to the detachment of the metal nanoparticles from the carbon support. Raman and X‐ray photoelectron spectroscopy show that these severe degradations are neither linked to massive corrosion of the carbon support nor to an overall change in carbon chemistry, but instead to a very localized corrosion of the carbon in the vicinity of the metal nanoparticles, leading to nucleation and growth of solid carbonate (when the electrolyte contains alkali metal cations), which expels the metal nanoparticles from their support. The mechanisms and extent of degradation depend on the nature of the metal nanoparticles, but also on their texture and on the nature of the support onto which they are immobilized. [ABSTRACT FROM AUTHOR]

Tin dioxide is a promising catalyst support to improve the stability of proton-exchange membrane fuel cells (PEMFC) cathodes at high voltages. However, optimizing the catalytic activity for the oxygen reduction reaction (ORR) of tin dioxide based electrocatalyst still remains challenging. In this study, an antimony doped tin dioxide (ATO) aerogel featuring suitable physico-chemical properties for application at a PEMFC cathode was successfully synthetized. Two platinum nanoparticles deposition methods were tested and compared. One is a chemical reduction route (using ethylene glycol, EG), the other uses ultraviolet (UV) irradiation followed by different thermal post-treatments. Electrocatalysts structure and morphology were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) experiments. The highest ORR mass activity measured in liquid electrolyte at 25°C was obtained for Pt/ATO from EG method (32 A gPt -1 versus 27 A gPt -1 for a reference Pt/HSAC 40 wt%). Pt/ATO turned out to be more stable than Pt/HSAC during an accelerated stress test composed of 5,000 potential cycles between 1.0 and 1.5 V vs. RHE at 80°C. [ABSTRACT FROM AUTHOR]

Metal Organic Frameworks (MOFs) have been recently proposed as promising electrocatalysts, yet the exact nature of the mechanisms in play has not been addressed in depth. By comparing the electrocatalytic activity of a MOF for the oxygen reduction reaction (ORR) and the corresponding molecular building units through electrochemical techniques, here, we investigate the nature of the catalytic sites, their redox states and the electron transfer pathways. [ABSTRACT FROM AUTHOR]

Pt/carbon xerogel (CX) catalysts were synthesized by the multiple strong electrostatic adsorption (SEA) method. This method consists of the impregnation of a carbon support (here, a CX) by a solution containing hexachloroplatinic acid (H2PtCl6). The impregnation pH is precisely chosen to maximize the ion/support interactions. The Pt precursor solution can be re-used so as to avoid Pt waste during the process. Five catalysts with increasing Pt weight percentage were synthesized by multiple impregnation (from one to five times), and were characterized by transmission electron microscopy, X-ray diffraction, and CO stripping. The specific activity of the Pt particles for the oxygen reduction reaction (ORR) was measured in liquid electrolyte with a rotating disk electrode system. The Pt particles are ca. 2.5 nm in diameter and display electroactive specific surface areas of ca. 95 cm2 gPt-1. The five Pt/CX catalysts present the same specific activity for the ORR: for all the catalysts, the specific activity equals ca. 0.05 mA cm-2Pt at 0.85 V versus NHE and 0.01 mA cm-2Pt at 0.9 V versus NHE. [ABSTRACT FROM AUTHOR]

This paper describes a versatile, light weight, and portable chamber dedicated to the transfer of electrodes from ultra-high vacuum (UHV) to atmospheric pressure and the liquid phase. This chamber can be connected to a liquid-phase reaction cell to perform electrochemical measurements and transfer back the electrode to the UHV environment. The experimental set-up can also be turned in order to make the electrode the bottom of the electrochemical cell. The validity and the efficiency of the experimental set-up were tested with a Pt(111) surface that provides unique electrochemical features in acidic sulphate-containing solution. This transfer chamber concept provides the surface science community with a new and versatile tool, complementary to existing systems, which allows fast electrolyte purging or electrochemical measurements under well-controlled mass transport conditions. [ABSTRACT FROM AUTHOR]

Abstract: IrO2, Ir x Sn(1−x)O2 (x =0.7, 0.5) and Ir x Ru(1−x)O2 (x =0.7, 0.5) electrocatalysts for the oxygen evolution reaction (OER) have been synthesized using the Adams fusion method. The metal oxides were characterized via X-ray diffraction, scanning electron microscopy, inductively coupled plasma–atomic emission spectrometry and nitrogen adsorption–desorption measurements to have information about their crystallographic structure, chemical composition and morphology, respectively. A controlled bulk molar fraction of Ru or Sn was introduced in the IrO2 lattice during the synthesis with no phase separation. The electrocatalytic activity of the synthesized oxides in the OER was studied in liquid electrolyte using porous rotating-disk electrodes, in “half-cell” configuration and in a 5cm2 proton-exchange membrane water electrolysis cell. An increase of the electrical performance was observed upon Ru insertion and a severe depreciation upon Sn insertion. [Copyright &y& Elsevier]

In this work, we operated a 16-cell proton-exchange membrane fuel cell (PEMFC) stack based on a Pt/C anode and a Pt3Co/C cathode under H2/air at constant current (j=0.6 A cm-2), temperature (T=70°C), relative humidity (RH) (anode: 0% RH, purge mode; cathode: 65% RH at the inlet), and pressure (1.3/1.1 bars absolute at the anode/cathode, respectively) for 1124 h. The membrane electrode assemblies were characterized with physical [field-emission gun-scanning electron microscopy (FEG-SEM), high resolution transmission electron microscopy, X-ray diffraction], electrochemical (cyclic voltammetry), and chemical (inductively coupled plasma-atomic emission spectrometry and X-ray energy-dispersive spectroscopy) techniques after different life stages, with special emphasis on the cathode electrocatalyst: as received (0 h), conditioned (17 h), and after 504 or 1124 h of aging. At the micrometer scale, FEG-SEM images reveal a very subtle degradation of the catalytic layers (thickness and density of defects). At the nanometer scale, the cyclic voltammograms of the cathode electrocatalyst point toward fast leaching of Co and formation of a "Pt skeleton" structure at the topmost surface layer within the first hours of operation. When the proton-exchange membrane fuel cell is operated for longer durations, two phenomena increase the "Pt character" of the electrocatalyst surface: Co surface segregation/leaching and Ostwald ripening. Consequently, the Pt-skeleton particles slowly evolve toward "Pt-shell/Pt-Co alloy core" structures with depleted Co content and a Pt-enriched shell (in the order of 2 atomic monolayers after 1124 h of operation). [ABSTRACT FROM AUTHOR]

Early reports stated that Au was a catalyst of choice for the BOR because it would yield a near complete faradaic efficiency. However, it has recently been suggested that gold could yield to some extent the heterogeneous hydrolysis of BH−4, therefore lowering the electron count per BH−4, especially at low potential. Actually, the blur will exist regarding the BOR mechanism on Au as long as no physical proof regarding the reaction intermediates is not put forward. In that frame, in situphysical techniques like FTIR exhibit some interest to study the BOR. Consequently, in situinfrared reflectance spectroscopy measurements (SPAIRS technique) have been performed in 1 M NaOH/1 M NaBH4on a gold electrode with the aim to detect the intermediate species. We monitored several bands in B–H (∼ 1180, 1080 and 972 cm−1) and B–O bond regions (= 1325 and ∼1425 cm−1), which appear sequentially as a function of the electrode polarization. These absorption bands are assigned to BH3, BH2and BO−2species. At the light of the experimental results, possible initial elementary steps of the BOR on gold electrode have been proposed and discussed according to the relevant literature data. [ABSTRACT FROM AUTHOR]

Abstract: Pt3Co/C electrocatalysts are not stable when operated in real PEMFC conditions but face variations of their chemical composition. The latter signs that Co atoms can segregate from the bulk to the surface of the nanoparticles, which we believe is activated by the formation of surface oxides and the leaching of Co at the surface. Consequently, the alloyed Pt3Co/C nanoparticles slowly evolve towards Pt shell/Pt–Co alloy core structures with depleted Co content and a Pt-enriched shell. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on the elaboration of PEMFC electrodes containing ultra-low platinum (Pt) loadings by direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD). DLI-MOCVD offers a large number of advantages for the elaboration of model PEMFC electrodes. First, by using different metal precursors or elaboration temperature, the size of the Pt nanoparticles and thus the intrinsic catalytic activity can easily be tailored in the nanometer range. In this work, Pt nanoparticles (1–5nm) with remarkable low degree of agglomeration and uniform distribution were deposited onto the microporous side of a commercial gas-diffusion layer (GDL). Second, reduction of the Pt loading is made possible by varying the Pt deposition time and its influence of the cell performance can be extracted without variation of the thickness of the catalytic layer (in previous studies, a decrease of the catalyst utilization was observed when increasing the Pt loading, i.e. the thickness of the catalytic layer (CL)). The electrocatalytic activity of home-made Pt nanoparticles elaborated by DLI-MOCVD was measured in liquid electrolyte or in complete fuel cell operating on H2/O2 or H2/air and compared vs. that of a commercially available electrode containing 500μgPt cm−2 (PtRef500). At the cathode, the performance of the electrodes containing 104–226μg of Pt per cm2 of electrode compares favorably with that of the PtRef500 in H2/O2 conditions. In H2/air conditions, additional mass-transport losses are detected in the low-current density region but the high effectiveness of our electrodes improves the performance in the high-current density region. At the anode, the Pt loading can be reduced to 35μgPt cm−2 without any voltage loss in agreement with previous observations. [Copyright &y& Elsevier]

Abstract: Well-defined tungsten-oxide-supported platinum nanoparticles (Pt/WO x ) were elaborated by impregnation-reduction of a platinum salt onto commercial monoclinic WO3. Field-emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM) revealed that the Pt particles are well-distributed on the oxide support, present a narrow particle size distribution centered on ca. 2–3nm and a low degree of agglomeration. Carbon black was added to ensure electronic percolation in the electrodes during the electrochemical measurements. COads electrooxidation currents were monitored at potentials as low as 0.1V vs. RHE on Pt/WO x , demonstrating high CO-tolerance compared to carbon-supported Pt or PtRu catalysts. [Copyright &y& Elsevier]

This paper (Part II) aims to provide an understanding of the degradations originating in the membrane or the binder and which dramatically affect the membrane electrode assembly performance and therefore the lifespan of protein exchange memory fuel cells. In Part I, evidence was provided of the corrosion of the platinum catalysts and the diffusion/migration through the membrane of platinum cations. In this paper we establish that these platinum cations induce physical cross-links that modify both the thermomechanical properties and the conductivities of the membrane. Since physical cross-links are reversible, ex Situ experiments were performed to recover the performance of pristine membranes by acidic treatment. Membrane performance was found to be much more affected in the case of membranes aged in the hot zone rather than in the cold zone. [ABSTRACT FROM AUTHOR]

We studied proton exchange membrane fuel cell membrane electrode assemblies (MEAs) degradation after fuel-cell operation. Anode and cathode pronounced degradation was monitored by chemical [energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS)], physical [scanning electron microscopy (SEM), transmission electron microscopy], and electrochemical (ultramicroelectrode with cavity) techniques. Aged MEAs underwent severe redistribution of most elements (Pt, C, F), coupled to a dramatic change of Pt particles shape, mean particle size and density over the carbon substrate. Among the various scenarios for Pt redistribution, Pt dissolution into Ptz+ species and transport in the ionomer or the proton exchange membrane play important roles. The Ptz+ dissolution/transport is likely favored by activators/ligands (F- or SOx-containing species) originating from the alteration of the polymers contained in the MEA. From SEM observations, the source of Ptz+ species is the cathode, while EDS and XPS show some SOS- and F-containing species origin from the anode. Local chemical analyses (SEM-EDS and XPS) revealed the excess Pt monitored in aged MEAs is associated with F excess. For instrumental limitation concerns, we could not detect the S element, but SOx-containing species could also act as counter ions during Ptz+ transport within the MEA. Pt corrosion/redistribution is associated with the decrease of Pt-active area as revealed by COad-stripping voltammograms. [ABSTRACT FROM AUTHOR]

The physical and chemical state of proton exchange membrane fuel cell (PEMFC) electrocatalysts (Pt/C) were investigated after 529 h of operation under fuel cell relevant conditions (333 K, 0.12 W cm-2) and 123 h of rest time under inert atmosphere (N2). Upon aging, pronounced corrosion of the cathode electrocatalyst (carbon-supported platinum nanoparticles: Pt/C) was evidenced by field-emission gun scanning electron microscopy (FEG-SEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical techniques. Carbon corrosion was witnessed by the decrease of the cathode thickness (-60%) and by the presence of nonsupported Pt particles inside the electrode. At the cathode, the corrosion of Pt nanoparticles produces Pt(*)z+ ions which diffuse in the ionomer phase or in solution [(*) stands for ionic species present in the ionomer phase or in solution]. These ions are highly mobile inside the membrane electrode assembly (MEA) and may cross over from the cathode to the anode through the PEM. The driving force for that is the electro-osmotic drag (if Pt(*)z+ ions combine with anions and carry a negative charge) and the chemical diffusion (concentration gradient of oxidized platinum species). Consequently, Pt(*)z+ ions were detected by ultraviolet (UV) spectroscopy in the PEM. Due to the high mobility of Pt(*)z+ ions, FEG-SEM and HRTEM analysis of the cross sections of MEAs revealed a pronounced change of Pt distribution after operation. Size distributions of both anode and cathode electrocatalysts evidenced an increase of the mean particle size, tailing toward large particle sizes and particle agglomeration. Nonspherical Pt nanoparticles were detected inside the PEM, the size and shape distribution of which strongly depend on the distance from the cathode. We believe PtPt(*)z+ ions are reduced chemically inside the membrane by H2 crossing over the PEM and both chemically and electrochemically at the anode/cathode. [ABSTRACT FROM AUTHOR]

Objectives: This study compared the accuracy of ultrasound cervical assessment (cervical length and cervical index) and digital examination (Bishop score and cervical score) in the prediction of spontaneous birth before 34 weeks in twin pregnancies. Methods: In a prospective multicenter study, digital examination and transvaginal sonography were performed consecutively in twin pregnancies attending for routine sonography at either 22 weeks (175 women) or 27 weeks (153 women). The digital examination took place first, and the Bishop score and cervical score (cervical length minus cervical dilatation) were calculated. Ultrasound measurements were then made of cervical length and funnel length to yield the cervical index (1 + funnel length/cervical length). The association between each variable and delivery before 34 weeks was tested by the Mann-Whitney U-test. The receiver-operating characteristics (ROC) curves of the ultrasound and digital indicators were determined for both gestational age periods, and the areas under the ROC curves compared. The best cut-off values for each indicator were used to determine predictive values for delivery before 34 weeks. Results: The median gestational age at delivery among the women included in the 22-week examination period was 36.0 (range, 21-40) weeks; 10.9% (19) gave birth spontaneously before 34 weeks. The median cervical length was 40 (range, 6-65) mm. All four parameters were predictors of delivery before 34 weeks. The areas under the ROC curves for cervical index, cervical length, Bishop score and cervical score did not differ significantly. The median gestational age at delivery among the women in the 27-week examination period was 36.0 (range, 27-40) weeks; 9.2% (14) gave birth spontaneously before 34 weeks. The median cervical length was 35 (range, 1-57) mm. All parameters except the Bishop score were predictors of delivery before 34 weeks. The likelihood ratio of the positive and negative tests for cervical length < or = 25 mm was 5.4 (range, 3.2-9.0) and 0.3 (range, 0.1-0.7), respectively, compared with 2.3 (range, 1.3-4.2) and 0.6 (range, 0.3-1.1), respectively, for cervical score < or = 1. The area under the curve for the cervical index was significantly larger than that for the Bishop score (P = 0.008) or cervical score (P = 0.02). Conclusion: Transvaginal sonography predicted spontaneous delivery before 34 weeks better than digital examination at the 27-week but not the 22-week examination. [ABSTRACT FROM AUTHOR]