RuO2 Nanostructure as an Efficient and Versatile Catalyst for H2 Photosynthesis

Photocatalytic H-2 generation holds promisein the greenproduction of alternative fuels and valuable chemicals. Seeking alternative,cost-effective, stable, and possibly reusable catalysts representsa timeless challenge for scientists working in the field. Herein,commercial RuO2 nanostructures were found to be a robust,versatile, and competitive catalyst in H-2 photoproductionin several conditions. We employed it in a classic three-componentsystem and compared its activities with those of the widely used platinumnanoparticle catalyst. We observed a hydrogen evolution rate of 0.137mol h(-1) g(-1) and an apparent quantumefficiency (AQE) of 6.8% in water using EDTA as an electron donor.Moreover, the favorable employment of l-cysteine as the electronsource opens possibilities precluded to other noble metal catalyst.The versatility of the system has also been demonstrated in organicmedia with impressive H-2 production in acetonitrile. Therobustness has been proved by the recovery of the catalyst by centrifugationand reusage alternatively in different media

ZnO Nanostructured Thin Films via Supersonic Plasma Jet Deposition

Zinc Oxide nanostructured thin films were grown by a novel plasma assisted vapour deposition method, which aims to combine the versatility of deposition processes that are mediated by plasma with the capability to control particles diffusion and nucleation. For this purpose, the proposed approach spatially separates into two different vacuum chambers the creation of zinc oxide from a metalorganic precursor from the actual film growth, thanks to the extraction of a supersonic jet of plasma seeded by the precursor fragments. The characterization of the reactor in different plasma conditions has been carried out by means of optical emission spectroscopy (OES). ZnO films with different degrees of purity, thickness uniformity, as well as different morphologies can be obtained varying the deposition parameters. The samples profiles have been collected in order to evaluate deposition rates and films uniformity. The as-prepared as well as annealed thin films were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to evaluate their chemical composition and purity. According to Raman analyses, the annealed samples are high-purity wurtzite-type crystalline zinc oxide films. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) confirm a surface morphology characterized by columnar structures

Controllable Synthesis of 2D Nonlayered Cr2S3 Nanosheets and Their Electrocatalytic Activity Toward Oxygen Evolution Reaction

The design of oxygen evolution reaction (OER) electrocatalysts based on Earth-abundant materials holds great promise for realizing practically viable water-splitting systems. In this regard, two-dimensional (2D) nonlayered materials have received considerable attention in recent years owing to their intrinsic dangling bonds which give rise to the exposure of unsaturated active sites. In this work, we solved the synthesis challenge in the development of a 2D nonlayered Cr2S3 catalyst for OER application via introducing a controllable chemical vapor deposition scheme. The as-obtained catalyst exhibits a very good OER activity requiring overpotentials of only 230 mV and 300 mV to deliver current densities of 10 mA cm−2 and 30 mA cm−2 , respectively, with robust stability. This study provides a general approach to optimize the controllable growth of 2D nonlayered material and opens up a fertile ground for studying the various strategies to enhance the water splitting reaction

Low Energy STEM of Multi-Layers and Dopant Profiles

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Advances in Focused Ion Beam Tomography for Three-Dimensional Characterization in Materials Science

Over the years, FIB-SEM tomography has become an extremely important technique for the three-dimensional reconstruction of microscopic structures with nanometric resolution. This paper describes in detail the steps required to perform this analysis, from the experimental setup to the data analysis and final reconstruction. To demonstrate the versatility of the technique, a comprehensive list of applications is also summarized, ranging from batteries to shale rocks and even some types of soft materials. Moreover, the continuous technological development, such as the introduction of the latest models of plasma and cryo-FIB, can open the way towards the analysis with this technique of a large class of soft materials, while the introduction of new machine learning and deep learning systems will not only improve the resolution and the quality of the final data, but also expand the degree of automation and efficiency in the dataset handling. These future developments, combined with a technique that is already reliable and widely used in various fields of research, are certain to become a routine tool in electron microscopy and material characterization

Hydrogen Desorption below 150 °c in MgH2-TiH2 Composite Nanoparticles: Equilibrium and Kinetic Properties

Reversible hydrogen sorption coupled with the MgH2 <-> Mg phase transformation was achieved in the remarkably low 340-425 K temperature range using MgH2-TiH2 composite nanoparticles obtained by reactive gas-phase condensation of Mg Ti vapors under He/H-2 atmosphere. The equilibrium pressures determined by in situ measurements at low temperature were slightly above those predicted using enthalpy Delta H and entropy Delta S of bulk magnesium. A single van't Hoff fit over a range extended up to 550 K yields the thermodynamic parameters Delta H = 68.1 0.9 kJ/molH(2) and Delta S = 119 2 J/(Kmo1H2) for hydride decomposition. A desorption rate of 0.18 wt % H-2/min was measured at T = 423 K and p(H-2) approximate to 1 mbar, i.e., close to equilibrium, without using a Pd catalysts. The nanoparticles displayed a small absorption desorption pressure hysteresis even at low temperatures. We critically discuss the influence exerted by nanostructural features such as interface free energy, elastic clamping, and phase mixing at the single nanopartide level on equilibrium and kinetic properties of hydrogen sorption

Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO2 Capture and Gas Separation

We fabricated novel composite (mixed matrix) membranes based on a permeable glassy polymer, Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and variable loadings of few-layer graphene, to test their potential in gas separation and CO2 capture applications. The permeability, selectivity and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured at 35 and 65 \u25e6C. Samples with small loadings of graphene show a higher permeability and He/CO2 selectivity than pure PPO, due to a favorable effect of the nanofillers on the polymer morphology. Higher amounts of graphene lower the permeability of the polymer, due to the prevailing effect of increased tortuosity of the gas molecules in the membrane. Graphene also allows dramatically reducing the increase of permeability with temperature, acting as a \u201cstabilizer\u201d for the polymer matrix. Such effect reduces the temperature-induced loss of size-selectivity for He/N2 and CO2/N2, and enhances the temperature-induced increase of selectivity for He/CO2. The study confirms that, as observed in the case of other graphene-based mixed matrix glassy membranes, the optimal concentration of graphene in the polymer is below 1 wt %. Below such threshold, the morphology of the nanoscopic filler added in solution affects positively the glassy chains packing, enhancing permeability and selectivity, and improving the selectivity of the membrane at increasing temperatures. These results suggest that small additions of graphene to polymers can enhance their permselectivity and stabilize their propertie

Biological application of Compressed Sensing Tomography in the Scanning Electron Microscope

The three-dimensional tomographic reconstruction of a biological sample, namely collagen fibrils in human dermal tissue, was obtained from a set of projection-images acquired in the Scanning Electron Microscope. A tailored strategy for the transmission imaging mode was implemented in the microscope and proved effective in acquiring the projections needed for the tomographic reconstruction. Suitable projection alignment and Compressed Sensing formulation were used to overcome the limitations arising from the experimental acquisition strategy and to improve the reconstruction of the sample. The undetermined problem of structure reconstruction from a set of projections, limited in number and angular range, was indeed supported by exploiting the sparsity of the object projected in the electron microscopy images. In particular, the proposed system was able to preserve the reconstruction accuracy even in presence of a significant reduction of experimental projections

Selective Electrodesorption-Based Atomic Layer Deposition (SEBALD) of Bismuth under Morphological Control

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