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Making a 3D character based on a concept is a classic way for artists to learn new tools and upgrade their skills, but creating your own design from scratch is [...]

Zeolites are crystalline microporous materials constructed by corner-sharing tetrahedra (SiO4and AlO4), with many industrial applications as ion exchangers, adsorbents and heterogeneous catalysts1, 2, 3–4. However, the presence of micropores impedes the use of zeolites in areas dealing with bulky substrates. Introducing extrinsic mesopores, that is, intercrystal/intracrystal mesopores, in zeolites is a solution to overcome the diffusion barrier5, 6, 7–8. Still, those extrinsic mesopores are generally disordered and non-uniform; moreover, acidity and crystallinity are always, to some extent, impaired9. Thus, synthesizing thermally stable zeolites with intrinsic mesopores that are of uniform size and crystallographically connected with micropores, denoted here as intrinsic mesoporous zeolite, is highly desired but still not achieved. Here we report ZMQ-1 (Zeolitic Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, no. 1), an aluminosilicate zeolite with an intersecting intrinsic meso-microporous channel system delimited by 28 × 10 × 10-rings, in which the 28-ring has a free diameter of 22.76 Å × 11.83 Å, which reaches the mesopore domain. ZMQ-1 has high thermal and hydrothermal stability with tunable framework Si/Al molar ratios. ZMQ-1 is the first aluminosilicate zeolite with an intrinsic meso-microporous channel system. The Brønsted acidity of ZMQ-1 imparts high activity and unique selectivity in the catalytic cracking of heavy oil. The position of the organic structure-directing agent (OSDA) used for ZMQ-1 synthesis was determined from three-dimensional electron diffraction (3D ED) data, which shows the unique structure-directing role of the OSDA in the formation of the intrinsic meso-microporous zeolite. This provides an incentive for preparing other stable mesopore-containing zeolites.

Downsizing zeolite crystals is a rational solution to address the challenge of slow adsorption rates for industrial applications. In this work, we report an environmentally friendly seed-assisted method for synthesizing nanoscale zeolite P, which has been shown to be promising for binary separations. The potassium-exchanged form of nanoagglomerates demonstrates dramatically enhanced CO2adsorption capacity, improved diffusion rate, and separation performance. Single-component CO2adsorption at equilibrium demonstrated higher CO2uptake and faster adsorption kinetics (ca. 1400 s vs >130000 s) for nanosized zeolite (KP1) compared to its micron-sized (KP2) counterpart. The diffusion kinetics analysis revealed the relation between the crystal size and the transport mechanism. The micron-sized KP2 sample was primarily governed by a surface barrier resistance mechanism, while in KP1, the diffusion process involved both intracrystalline and surface barrier resistance, facilitating the surface diffusion process and enhancing the overall diffusion rate. Breakthrough curve analysis confirmed these findings as fast and efficient CO2/N2and CO2/CH4separations recorded for the nanosized sample. The results showed remarkably enhanced breakthrough time for KP2 vs KP1 in CO2/N2(1.0 vs 10.9 min) and CO2/CH4(1.1 vs 9.9 min) mixtures, along with much higher adsorption capacity for CO2/N2(0.18 vs 1.33 mmol/g) and CO2/CH4(0.18 vs 1.21 mmol/g) mixtures. The set of experimental data demonstrates the importance of zeolite crystal engineering for improving the gas separation performance of processes involving CO2, N2, and CH4.

Adsorption on various adsorbents of hydrogen and helium at temperatures close to their boiling points shows, in some cases, unusually high monolayer capacities. The microscopic nature of these adsorbate phases at low temperatures has, however, remained challenging to characterize. Here, using high-resolution cryo-adsorption studies together with characterization by inelastic neutron scattering vibration spectroscopy, we show that, near its boiling point (~20 K), H2adsorbed on a well-ordered mesoporous silica forms a two-dimensional monolayer with a density more than twice that of bulk-solid H2, rather than a bilayer. Theoretical studies, based on thorough first-principles calculations, rationalize the formation of such a super-dense phase. The strong compression of the hydrogen surface layer is due to the excess of surface–hydrogen attraction over intermolecular hydrogen repulsion. Use of this super-dense hydrogen monolayer on an adsorbent might be a feasible option for the storage of hydrogen near its boiling point, compared with adsorption at 77 K.

Alignment of metal–organic framework (MOF) crystals has previously been performed via careful control of oriented MOF growth on substrates, as well as by dynamic magnetic alignment. We show here that bromobenzene-suspended microrod crystals of the MOF NU-1000 can also be dynamically aligned via electric fields, giving rise to rapid electrooptical responses. This method of dynamic MOF alignment opens up new avenues of MOF control which are important for integration of MOFs into switchable electronic devices as well as in other applications such as reconfigurable sensors or optical systems.

Regarding the design of SBA-15 silica, substantial efforts were deployed in the past decade in order to understand the mechanism of formation and the effects of the different synthesis conditions on the structure and porosity of the resulting materials. However, better insights into both the tailoring and the characterization of the pore structure of such mesoporous materials are still needed in order to enable the accurate control of adsorption and pore condensation properties in SBA-15. For this, the influence of the synthesis parameters on the properties of SBA-15 silica must be rationalized in terms of their implications for pore architecture, i.e., pore structure and network interconnectivity. Herein, it is demonstrated that pore condensation and hysteresis behavior of inert gases in subcritical conditions confined in ordered mesoporous SBA-15 silica can precisely be modulated as a function of the synthesis parameters. Synthesis conditions were found for generating SBA-15 samples that can be described entirely as a pseudo one-dimensional (1-D) pore system (i.e., pore condensation and hysteresis behavior are an intrinsic property of the liquid–vapor transition in a finite volume, in agreement with the independent open pore model). However, the data also revealed that distinct synthesis conditions allow for the preparation of SBA-15 with pore condensation properties affected by cooperative pore network effects, mimicking the behavior observed for materials with a pristinethree-dimensional (3-D) interconnected pore network topology, such as KIT-6 silica. Therefore, this comprehensive study shows that SBA-15 should be best regarded as a family of solids with easily adjustable porosity, ranging from corrugated and/or distorted pore systems to highly interconnected networks of channels. The effect of each different synthesis parameter on the final pore size of SBA-15 was carefully monitored, and a threshold acid concentration range for optimal pore size variation was found. In addition to substantial progress in the SBA-15 synthesis, such in-depth characterization of a “model” ordered mesoporous material coupled with advanced application of state-of-the-art NLDFT methods is of prime importance both for the development of fundamental research on the topic and for the applications requiring tailored high surface area materials with selectively tuned pore structure.

The CO2adsorption performance of a zeolite is related to the framework structure and extra-framework composition. In this work, parent Na-GIS and partially exchanged NaMg1-GIS and NaMg3-GIS, with 30 and 50% degree of Mg2+exchange, respectively, were prepared. Further, the series of zeolites were thoroughly characterized and studied for their applicability for CO2adsorption and CO2/N2and CO2/CH4separations by single-component adsorption and dynamic breakthrough curve analysis methods. The lower concentration of Mg2+cations in NaMg1-GIS resulted in enhanced CO2adsorption due to beneficial distortion of the framework pore structure, making the adsorption of N2and CH4more challenging. However, this benefit was lost for higher Mg2+concentration (NaMg3-GIS) due to a more pronounced framework distortion, impairing not only the adsorption of N2and CH4but also the CO2one, ultimately leading to a loss of selectivity. The molecular dynamics simulations and density functional theory (DFT) calculations, aligned with experimental data, reveal an elevated heat of adsorption for CO2in NaMg3-GIS due to framework deformation caused by Mg2+cations. Consistent with the adsorption equilibrium experiments, the ternary dynamic experiments of CO2/N2/He evaluated by breakthrough curve analysis show a higher CO2/N2selectivity of 1673 and 1248 at 25 and 50 °C, respectively, for the NaMg1-GIS sample. For the CO2/CH4/He experiments, the CO2/CH4selectivity tended toward extremely high values due to negligible CH4uptake on NaMg1-GIS. In addition, the better dynamic adsorption/separation of CO2on NaMg1-GIS is ascribed to the greater distortion of the pore aperture due to the presence of Mg2+cations, affecting the diffusion of small molecules. Overall, our results demonstrate the high potential of NaMg-GIS materials for critically important energy separation processes involving CO2, N2, and CH4.

The efficient separation and adsorption of critical gases are, more than ever, a major focus point in important energy processes, such as CH4enrichment of biogas or natural gas, CO2separation and capture, and H2purification and storage. Thanks to its physicochemical properties, cation-exchanged chabazite is a potent zeolite for such applications. Previous computational screening investigations have mostly examined chabazites exchanged with monovalent cations. Therefore, in this contribution, periodic density functional theory (DFT) calculations in combination with dispersion corrections have been used for a systematic screening of divalent cation exchanged chabazite zeolites. The work focuses on cheap and readily available divalent cations, Ca(II), Mg(II), and Zn(II), Fe(II), Sn(II), and Cu(II) and investigates the effect of the cation nature and location within the framework on the adsorption selectivity of chabazite for specific gas separations, namely, CO2/CH4, N2/CH4, and N2/H2. All the cationic adsorption sites were explored to describe the diversity of sites in a typical experimental chabazite with a Si/Al ratio close to 2 or 3. The results revealed that Mg-CHA is the most promising cation for the selective adsorption of CO2. These predictions were further supported by ab initiomolecular dynamics simulations performed at 300 K, which demonstrated that the presence of CH4has a negligible impact on the adsorption of CO2on Mg-CHA. Ca(II) was found to be the most favorable cation for the selective adsorption of H2and CO2. Finally, none of the investigated cations were suitable for the preferential capture of N2and H2in the purification of CH4rich mixtures. These findings provide valuable insights into the factors influencing the adsorption behavior of N2, H2, CH4, and CO2and highlight the crucial role played by theoretical calculations and simulations for the optimal design of efficient adsorbents.

Ru and Ir based materials were prepared by the thermal decomposition of polymeric precursor's method. The anode catalysts free from carbon substrate were obtained by tailoring the reaction process to avoid occurrence of CO2 formation during water electrolysis. Various Ir contents were added in the Ru catalytic compositions for improving the oxidation-resistance of RuO2 which was the best metallic oxide in H2O splitting. Their physical characterizations revealed the presence of agglomerates due probably to the heat treatment process consisting in the removal of organic carbon at 400 oC. The prevalent existence of RuO2 and IrO2 in the anode materials was confirmed by XPS experiments and the electrochemical measurements enabled to show that RuxIr1-xO2 materials were more active towards water oxidation than IrO2 catalyst. The O2 evolution process started at 1.45 V with Ru0.9Ir0.1O2 in the anodic compartment of a 25 cm2 Proton Exchange Membrane Water Electrolyzer at 60oC.

Mesoporous silica nanoparticles (MSNs) are of growing interest for the development of novel probes enabling efficient tracking of cells in vivo using magnetic resonance imaging (MRI). The incorporation of Gd3+paramagnetic ions into highly porous MSNs is a powerful strategy to synthesize “positive” MRI contrast agents for more quantitative T1‐weighted MR imaging. Within this context, different strategies have been reported to integrate Gd chelates to 2D pore network MSNs. As an alternative, we report on the modulation of the pore network topology through the preparation of a 3D pore network hybrid GdSixOyMSN system. In this study, 2D GdSixOy‐MSNs with similar porosity and particle size were also prepared and the relaxometric performances of both materials, directly compared. Both syntheses lead to water‐dispersible MSNs suspensions (particle size < 200 nm), which were stable for at least 48h. 3D GdSixOy‐MSNs provided a significant increase in 1H longitudinal relaxivity (18.5 s−1mM−1; 4.6 times higher than Gd‐DTPA) and low r2/r1ratios (1.56) compatible with the requirements of “positive” contrast agents for MRI. These results demonstrate the superiority of a 3D pore network to host paramagnetic atoms for MRI signal enhancement using T1‐weighted imaging. Such an approach minimizes the total amount of paramagnetic element per particle.

The influence of pore surface functionalities in mesoporous SBA‐15 silica on the stability of a model olefin metathesis catalyst, namely Grubbs I, is substantiated. In particular, it is demonstrated that the nature of the interaction between the ruthenium complex and the surface is strongly depending on the presence of surface silanols. For this study, differently functionalized mesoporous SBA‐15 silica materials were synthesized according to standard procedures and, subsequently, the Grubbs I catalyst was incorporated into these different host materials. All of the materials were thoroughly characterized by elemental analyses, nitrogen physisorption at −196 °C, thermogravimetric analyses, solid‐state NMR spectroscopy, and infrared spectroscopy (ATR‐IR). By such in‐depth characterization of the materials, it became possible to achieve models for the surface/catalyst interactions as a function of surface functionalities in SBA‐15; for example, in the case of purely siliceous silanol‐rich SBA‐15, octenyl‐silane modified SBA‐15, and silylated equivalents. It was evidenced that large portions of the chemisorbed species that are detected spectroscopically arise from interactions between the tricyclohexylphosphine and the surface silanols. A catalytic study using diethyldiallylmalonate in presence of the various functionalized silicas shows that the presence of surface silanols significantly decreases the longevity of the ring‐closing metathesis catalyst, whereas the passivation of the surface by trimethylsilyl groups slows down the catalysis rate, but does not affect significantly the lifetime of the catalyst. This contribution thus provides new insights into the functionalization of SBA‐15 materials and the role of surface interactions for the grafting of organometallic complexes.

Robuste Elektrokatalysatorenfür die H2‐Freisetzung und ‐Aufnahme entstehen durch Funktionalisierung mehrwandiger Kohlenstoffnanoröhren mit molekularen Komplexen über π‐Stapelung. Die edelmetallfreien Nanomaterialien haben Vorteile gegenüber herkömmlichen Platinkatalysatoren, weil sie kompatibel mit den Arbeitsbedingungen in Protonenaustauschmembran‐Systemen und unempfindlich gegen CO sind.

In this paper, we present experimental results on the preparation and the electrochemical characterization of electrocatalytic particles with homogeneous composition, modeled by Franco et al. [ J. Electrochem. Soc. , 156 , B410 (2009) ]. Preparation is made through the direct liquid injection metallorganic chemical vapor deposition technique previously developed at CEA, and electrochemical analysis is carried out by using a rotating disk electrode and membrane-assembled gas diffusion electrode. Degradation structural changes are characterized by using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Optimal Co compositions are identified for better oxygen reduction reaction activity and durability, validating the modeling studies.

In order to investigate the details of the process of pore condensation and hysteresis mechanisms in three-dimensional (3-D) pore networks, we performed a systematic study of the adsorption and pore condensation behavior of N2(77.4 K) and Ar (77.4 and 87.3 K) in a 3-D ordered pore system, i.e., cubic Ia3̅dmesoporous KIT-6 silica materials with mode pore diameters ranging from ca. 5 nm up to 11 nm. KIT-6 silica is a porous material composed of two intertwined mesoporous subnetworks similar as in MCM-48, but this material can be prepared with much larger mean pore diameters. Accurate pore size analysis was performed by X-ray diffraction modeling and by state-of the art application of nonlocal density functional theory (NLDFT) on N2(77.4 K) and Ar (87.3 K) sorption data. Furthermore, our data suggest that the width of the adsorption/desorption hysteresis loop observed for 3-D KIT-6 silica can be narrower as compared to that of pseudo-one-dimensional SBA-15 silica of the same pore size (i.e., in the pore diameter range from 6 to 8 nm). This specific behavior correlates well with the existence of the highly interconnected 3-D pore network of the KIT-6 material. Moreover, the results of our investigations are also consistent with previous observations that the SBA-15 pore system becomes more and more interconnected with increasing aging temperatures, i.e., SBA-15 changes from being a material with a pseudo-one-dimensional mesopore system to a material exhibiting a three-dimensional pore system resembling KIT-6 silica. These results provide new insights into the effects of pore interconnectivity on pore condensation and hysteresis behavior in both KIT-6 and SBA-15 silica materials and enable a more thorough understanding of the pore structure and textural properties of these materials.

In this article, we focus on the understanding of the electrocatalysts degradation in polymer electrolyte fuel cell (PEFC) environments. A multiscale atomistic/kinetic model is derived providing mechanistic insights on the impact of the nanostructure and operating conditions on nanoparticles durability. On the basis of ab initio (AI) data, we identify favorable pathways of the oxygen reduction reaction (ORR) on nanoparticles and of the competitive Pt-Co dissolution in acidic media. The derived AI kinetics is coupled to a description of the atomic reorganization at the nanoparticle level as a function of the cumulated Pt and Co mass losses. This nanoscale model is coupled with a transport microscale model of charges and through a PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed and complimented by microstructural and electrochemical characterizations carried out on aging direct liquid injection metallorganic chemical vapor deposition elaborated model electrodes detailed in our experimental companion paper.

In this paper we focus on the understanding of the PtxCoy catalysts degradation in PEFC environments. A multiscale atomistic/kinetic model is derived providing new mechanistic insights on the impact of clusters nanostructure and operating conditions on PtxCoy materials durability. On the basis of ab initio (AI) data, we identify favorable pathways of the ORR on PtxCoy clusters and of the competitive Pt-Co dissolution in acidic media. The derived AI-kinetics is coupled to a description of the atomic reorganisation at the cluster level as function of the cumulated Pt and Co mass losses. This interfacial model is coupled with a transport microscale model of charges and O2 through the PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed. Experiments on DLIMOCVD-elaborated model electrodes are carried out by using RDE and half-cells: degradation structural changes are characterized by using TEM, XRD and XPS complementing the modeling studies.

Ru and Ir based materials were prepared by the thermal decomposition of polymeric precursor's method. The anode catalysts free from carbon substrate were obtained by tailoring the reaction process to avoid occurrence of CO2formation during water electrolysis. Various Ir contents were added in the Ru catalytic compositions for improving the oxidation-resistance of RuO2which was the best metallic oxide in H2O splitting. Their physical characterizations revealed the presence of agglomerates due probably to the heat treatment process consisting in the removal of organic carbon at 400 ºC. The prevalent existence of RuO2 and IrO2 in the anode materials was confirmed by XPS experiments and the electrochemical measurements enabled to show that RuxIr1-xO2materials were more active towards water oxidation than IrO2catalyst. The O2evolution process started at 1.45 V with Ru0.9Ir0.1O2in the anodic compartment of a 25 cm2Proton Exchange Membrane Water Electrolyzer at 60ºC.

Abstract not Available.

Abstract not Available.

Increasing lifetime and performance is critical for proton exchange membrane fuel cell (PEMFC) using stainless steel plates. A good compromise between passivity and electrical contact resistance of the plate material is required. Measuring the potential of each plate during fuel cell operation is of paramount importance to lead to relevant ex situ tests in order to investigate new materials. From a review on methods used for potential measurements, the present work focused on the realization and use of a dynamic hydrogen electrode (DHE) device as a reference electrode in a PEMFC single cell and its evaluation in terms of accuracy and drift. With classic reference electrodes introduced into the flow field, measurements were shown to be irrelevant because of the impossibility to ensure good and stable ionic conductivity between the reference electrode and the plate when operating the cell. Several examples of DHE found in the literature were reviewed and used to realize a DHE, which showed correct accuracy and stability of its potential under fully humidified conditions. The experimental device was shown to be reliable and easily adaptable for different single cells. It was used to investigate transient phenomena while cycling a cell, but needs some improvement when the cell is operated with unsaturated gases.

In this paper, we present experimental results on the preparation and the electrochemical characterization of PtxCoyelectrocatalytic particles with homogeneous composition, modeled by Franco et al. [ J. Electrochem. Soc. , 156 , B410 (2009) ]. Preparation is made through the direct liquid injection metallorganic chemical vapor deposition technique previously developed at CEA, and electrochemical analysis is carried out by using a rotating disk electrode and membrane-assembled gas diffusion electrode. Degradation structural changes are characterized by using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Optimal Co compositions are identified for better oxygen reduction reaction activity and durability, validating the modeling studies.

In this article, we focus on the understanding of the PtxCoyelectrocatalysts degradation in polymer electrolyte fuel cell (PEFC) environments. A multiscale atomistic/kinetic model is derived providing mechanistic insights on the impact of the nanostructure and operating conditions on PtxCoynanoparticles durability. On the basis of ab initio (AI) data, we identify favorable pathways of the oxygen reduction reaction (ORR) on PtxCoynanoparticles and of the competitive Pt–Co dissolution in acidic media. The derived AI kinetics is coupled to a description of the atomic reorganization at the nanoparticle level as a function of the cumulated Pt and Co mass losses. This nanoscale model is coupled with a transport microscale model of charges and O2through a PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed and complimented by microstructural and electrochemical characterizations carried out on aging direct liquid injection metallorganic chemical vapor deposition elaborated model electrodes detailed in our experimental companion paper.