Enhanced Stability of Iridium Nanocatalysts via Exsolution for the CO₂ Reforming of Methane

\ua9 2023 The Authors. Published by American Chemical Society. The reforming reactions of greenhouse gases require catalysts with high reactivity, coking resistance, and structural stability for efficient and durable use. Among the possible strategies, exsolution has been shown to demonstrate the requirements needed to produce appropriate catalysts for the dry reforming of methane, the conversion of which strongly depends on the choice of active species, its interaction with the support, and the catalyst size and dispersion properties. Here, we exploit the exsolution approach, known to produce stable and highly active nanoparticle-supported catalysts, to develop iridium-nanoparticle-decorated perovskites and apply them as catalysts for the dry reforming of methane. By studying the effect of several parameters, we tune the degree of exsolution, and consequently the catalytic activity, thereby identifying the most efficient sample, 0.5 atomic % Ir-BaTiO3, which showed 82% and 86% conversion of CO2 and CH4, respectively. By comparison with standard impregnated catalysts (e.g., Ir/Al2O3), we benchmark the activity and stability of our exsolved systems. We find almost identical conversion and syngas rates of formation but observe no carbon deposition for the exsolved samples after catalytic testing; such deposition was significant for the traditionally prepared impregnated Ir/Al2O3, with almost 30 mgC/gsample measured, compared to 0 mgC/gsample detected for the exsolved system. These findings highlight the possibility of achieving in a single step the mutual interaction of the parameters enhancing the catalytic efficiency, leading to a promising pathway for the design of catalysts for reforming reactions

Low-temperature exsolution of Ni-Ru bimetallic nanoparticles from A-site deficient double perovskites

Exsolution of stable metallic nanoparticles for use as efficient electrocatalysts has been of increasing interest for a range of energy technologies. Typically, exsolved nanoparticles show higher thermal and coarsening stability compared to conventionally deposited catalysts. Here, A-site deficient double perovskite oxides, La2-xNiRuO6-δ (x = 0.1 and 0.15), are designed and subjected to low-temperature reduction leading to exsolution. The reduced double perovskite materials are shown to exsolve nanoparticles of 2–6 nm diameter during the reduction in the low-temperature range of 350–450 °C. The nanoparticle sizes are found to increase after reduction at the higher temperature (450 °C), suggesting diffusion-limited particle growth. Interestingly, both nickel and ruthenium are co-exsolved during the reduction process. The formation of bimetallic nanoparticles at such low temperatures is rare. From the in situ impedance spectroscopy measurements of the double perovskite electrode layers, the onset of the exsolution process is found to be within the first few minutes of the reduction reaction. In addition, the area-specific resistance of the electrode layers is found to decrease by 90% from 291 to 29 Ω cm2, suggesting encouraging prospects for these low-temperature rapidly exsolved Ni/Ru alloy nanoparticles in a range of catalytic applications

Water-peptide dynamics during conformational transitions

Transitions between metastable conformations of a dipeptide are investigated using classical molecular dynamics simulation with explicit water molecules. The distribution of the surrounding water at different moments before the transitions and the dynamical correlations of water with the peptide's configurational motions indicate that the water molecules represent an integral part of the molecular system during the conformational changes, in contrast to the metastable periods when water and peptide dynamics are essentially decoupled

DETERMINATION OF TYPES OF INDIVIDUALS IN APHIDS, ROTIFERS AND CLADOCERA 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72827/1/j.1469-185X.1929.tb00888.x.pd

Floating macro litter in European rivers - top items

The JRC exploratory project RIMMEL provides information about litter, mainly plastic waste, entering the European Seas through river systems. RIMMEL has collected data on riverine floating macro litter inputs to the sea. Data acquisition was based on the Riverine Litter Observation Network (RiLON) activities, which collected data from rivers in the European marine basins over a period of one year (September 2016 – September 2017). Data was collected by visual observations and documented with the JRC Floating Litter Monitoring Application for mobile devices, allowing a harmonized reporting, compatible with the MSFD Master List of Categories for Litter Items. This report includes the Top Items lists of riverine floating macro litter, based on the total amount of litter items identified during RiLON activities and ranked by abundance. Top Items lists have been elaborated considering the whole database for the European Seas and further detailed for each individual European regional sea: Baltic Sea, Black Sea, Mediterranean Sea and North-East Atlantic. The North-East Atlantic and the Mediterranean Sea regions showed similar litter categories in their Top 20 Items. These two regions provided most of the available data, influencing the general Top Items list. In the Black Sea and Baltic Sea regions, where data availability was limited, the Top Items lists showed more differences among the different regions. Overall, the general Top Items list for the European Seas showed a predominance of plastic item categories (artificial polymer materials). As a whole, plastic items made up to 80.8% of all objects, with plastic and polystyrene fragments comprising 45% of the identified items in the database. Additionally, Single Use Plastics such as bottles, cover/packaging and bags were also ranked among the most frequently found floating litter. The similarities in the Top 10 and Top 20 items for the different regions, and the appearance of Single Use Plastics scoring high in the ranking, support the need for common actions against plastic pollution at EU level.JRC.D.2-Water and Marine Resource

Low-power linear-phase delay filters for neural signal processing: comparison and synthesis

International audienc

Oxygen diffusion behaviour of A-site deficient (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ perovskites in humid conditions

In the development of high temperature electrochemical devices such as oxygen transport membranes (OTMs) and solid oxide fuel cells (SOFCs), solid-state (ceramic) technologies have proven to be particularly promising. For example, doped lanthanum chromite perovskites, which display high thermo-chemical stability in aggressive environments as mixed ionic and electronic conducting (MIEC) perovskite electrodes, show potential for use as OTMs. Previous studies on the range of these MIEC perovskites have focussed on material behaviour under pure oxygen conditions. Recently, however, it has been suggested that components of air such as humid vapour may modify the materials' chemistry under device operating conditions, affecting device performance and durability. We have designed and carried out fundamental research into the effect of humidity on the oxygen surface exchange and diffusion kinetics of a commercialized (La0.8Sr0.2)0.95Cr0.5Fe0.5O3−δ (LSCrF8255) perovskite material under elevated OTM and SOFC operating conditions. The water surface exchange and oxygen ion diffusion behaviour of LSCrF8255 perovskites were measured through Isotopic Exchange Depth Profiling-Secondary Ion Mass Spectrometry (IEDP-SIMS) in a designed humid condition with an oxygen partial pressure of 200 mbar and a constant water vapour pressure of 30 mbar, from intermediate to high temperatures (600 °C to 900 °C). Our study demonstrates consistency between oxygen ion bulk diffusion kinetics in wet (pO2 = 200 mbar, pH2O = 30 mbar) and dry (pO2 = 200 mbar, pH2O = 0 mbar) oxygen atmospheres. However, limited surface exchange between water and the LSCrF material was observed above 800 °C. To study the limited water surface exchange behaviour, angle-resolved X-ray photoelectron spectroscopy (ARXPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) have been applied to correlate the changes in water surface exchange with chemical or topographic changes in the materials, such as Sr surface segregation processes. It was found that Sr segregation is one of the factors suppressing water surface exchange, although not the primary limiting factor. Another limiting factor was found through in situ residual gas analysis (RGA), which showed the dominance of homo-exchange between the humid vapour and gaseous oxygen molecules at high temperatures

Broadband Sounding Rocket Antenna for Dual-Band Telemetric and Payload Data Transmission

International audienceThis paper presents and investigates a broadband sounding rocket antenna developed for dual-band data transmission of telemetric and payload systems. This single-element antenna permits the use of both the well-established 869.4-869.65 MHz and 2.4-2.4835 GHz frequency bands available in Europe to implement a redundant transmission of telemetric and tracking data desired for reliability. Furthermore, the available spectrum in the upper band offers a high-speed wireless link for transmitting payload data. To preserve the mechanical integrity and aerodynamics of rocket, the antenna is integrated in its nose cone. The proposed low-cost and low-weight structure is based on PCB (Printed Circuit Board) pieces assembled in a LEGO-like manner to form a broadband 3-Dimentional (3-D) bi-conical antenna, which is fed by a diplexer integrated in its base. A prototype has been fabricated, and validated using a reduced-length fuselage in a near-field measurement system