Silicalite-1 Layer Secures the Bifunctional Nature of a CO2 Hydrogenation Catalyst.

Close proximity usually shortens the travel distance of reaction intermediates, thus able to promote the catalytic performance of CO2 hydrogenation by a bifunctional catalyst, such as the widely reported In2O3/H-ZSM-5. However, nanoscale proximity (e.g., powder mixing, PM) more likely causes the fast deactivation of the catalyst, probably due to the migration of metals (e.g., In) that not only neutralizes the acid sites of zeolites but also leads to the reconstruction of the In2O3 surface, thus resulting in catalyst deactivation. Additionally, zeolite coking is another potential deactivation factor when dealing with this methanol-mediated CO2 hydrogenation process. Herein, we reported a facile approach to overcome these three challenges by coating a layer of silicalite-1 (S-1) shell outside a zeolite H-ZSM-5 crystal for the In2O3/H-ZSM-5-catalyzed CO2 hydrogenation. More specifically, the S-1 layer (1) restrains the migration of indium that preserved the acidity of H-ZSM-5 and at the same time (2) prevents the over-reduction of the In2O3 phase and (3) improves the catalyst lifetime by suppressing the aromatic cycle in a methanol-to-hydrocarbon conversion step. As such, the activity for the synthesis of C2 + hydrocarbons under nanoscale proximity (PM) was successfully obtained. Moreover, an enhanced performance was observed for the S-1-coated catalyst under microscale proximity (e.g., granule mixing, GM) in comparison to the S-1-coating-free counterpart. This work highlights an effective shielding strategy to secure the bifunctional nature of a CO2 hydrogenation catalyst.

Interface Design Enabling Stable Polymer/Thiophosphate Electrolyte Separators for Dendrite-Free Lithium Metal Batteries.

Organic/inorganic interfaces greatly affect Li+ transport in composite solid electrolytes (SEs), while SE/electrode interfacial stability plays a critical role in the cycling performance of solid-state batteries (SSBs). However, incomplete understanding of interfacial (in)stability hinders the practical application of composite SEs in SSBs. Herein, chemical degradation between Li6 PS5 Cl (LPSCl) and poly(ethylene glycol) (PEG) is revealed. The high polarity of PEG changes the electronic state and structural bonding of the PS4 3- tetrahedra, thus triggering a series of side reactions. A substituted terminal group of PEG not only stabilizes the inner interfaces but also extends the electrochemical window of the composite SE. Moreover, a LiF-rich layer can effectively prevent side reactions at the Li/SE interface. The results provide insights into the chemical stability of polymer/sulfide composites and demonstrate an interface design to achieve dendrite-free lithium metal batteries.

Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells.

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr2O3. The aim of the present study was to investigate whether Cr(III) particles exerted properties comparable to water soluble Cr(III) or to Cr(VI), including two nano-sized and one micro-sized particles. The morphology and size distribution were determined by TEM, while the oxidation state was analyzed by XPS. Chromium release was quantified via AAS, and colorimetrically differentiated between Cr(VI) and Cr(III). Furthermore, the toxicological fingerprints of the Cr2O3 particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr2O3 particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. Even though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content.

Tuning the optical properties of 2D monolayer silver-bismuth bromide double perovskite by halide substitution.

Silver-bismuth double perovskites are promising replacement materials for lead-based ones in photovoltaic (PV) devices due to the lower toxicity and enhanced stability to environmental factors. In addition, they might even be more suitable for indoor PV, due to the size of their bandgap better matching white LEDs emission. Unfortunately, their optoelectronic performance does not reach that of the lead-based counterparts, because of the indirect nature of the band gap and the high exciton binding energy. One strategy to improve the electronic properties is the dimensional reduction from the 3D to the 2D perovskite structure, which features a direct band gap, as it has been reported for 2D monolayer derivates of Cs2AgBiBr6obtained by substituting Cs+cations with bulky alkylammonium cations. However, a similar dimensional reduction also brings to a band gap opening, limiting light absorption in the visible. In this work, we report on the achievement of a bathochromic shift in the absorption features of a butylammonium-based silver-bismuth bromide monolayer double perovskite through doping with iodide and study the optical properties and stability of the resulting thin films in environmental conditions. These species might constitute the starting point to design future sustainable materials to implement as active components in indoor photovoltaic devices used to power the IoT.

Lithium-Metal Anode Instability of the Superionic Halide Solid Electrolytes and the Implications for Solid-State Batteries.

Owing to high ionic conductivity and good oxidation stability, halide-based solid electrolytes regain interest for application in solid-state batteries. While stability at the cathode interface seems to be given, the stability against the lithium metal anode has not been explored yet. Herein, the formation of a reaction layer between Li3 InCl6 (Li3 YCl6 ) and lithium is studied by sputter deposition of lithium metal and subsequent in situ X-ray photoelectron spectroscopy as well as by impedance spectroscopy. The interface is thermodynamically unstable and results in a continuously growing interphase resistance. Additionally, the interface between Li3 InCl6 and Li6 PS5 Cl is characterized by impedance spectroscopy to discern whether a combined use as cathode electrolyte and separator electrolyte, respectively, might enable long-term stable and low impedance operation. In fact, oxidation stable halide-based lithium superionic conductors cannot be used against Li, but may be promising candidates as cathode electrolytes.

Halide ion influence on the formation of nickel nanoparticles and their conversion into hollow nickel phosphide and sulphide nanocrystals.

A dependence of the formation of tri-n-octylphosphine-capped Ni nanocrystals on the presence of halide ions during their synthesis is shown. For the application-oriented synthesis of Ni particles, this information can be crucial. Furthermore, Ni nanoparticles can be converted to nickel phosphide or sulphide by heating them up in the presence of a phosphorus or sulphur source, resulting in either solid or hollow nanocrystals, formed via the nanoscale Kirkendall effect, depending on the synthesis route. By adjusting the Ni crystallite size in the initial nanoparticles via the halide ion concentration the cavity size of the resulting hollow nanocrystals can be tuned, which is otherwise impossible to realise for particles of a similar total diameter by using this process. The synthesised hollow Ni3S2 nanocrystals exhibit a much sharper localised surface plasmon resonance (LSPR) band than all previously presented particles of this material, which is known to show molar extinction coefficients at the LSPR maximum similar to Au. This narrow linewidth could be explained by the nanoparticles' high crystallinity resulting from the Kirkendall process and is interesting for various possible optical applications such as surface-enhanced Raman spectroscopy owing to the low cost of the involved materials compared to the widely used noble metals.

Homogeneous Coating with an Anion-Exchange Ionomer Improves the Cycling Stability of Secondary Batteries with Zinc Anodes.

Limited cycling stability of secondary cells with zinc anodes arises mainly from the high solubility of oxidized zinc species in the alkaline electrolyte resulting in electrode shape change and loss of active material during repeated discharge and charge. We propose and successfully employ a homogeneous coating with an anion-exchange ionomer (AEI) on model electrodes with electron-conductive host structures to confine the oxidized zinc species. Ideally, the confinement of oxidized zinc species reduces the shape change of the electrode and keeps the active material as close as possible at its place of origin. In this work, the confinement concept for the oxidized zinc species is elucidated by means of electrochemical studies and X-ray photoelectron spectroscopy: as intended, an interlayer of zinc oxide forms between the AEI and the surface of the zinc electrode. This interlayer implies that the hydroxide ions are able to pass and react as intended, whereas the migration of oxidized zinc species into the bulk electrolyte is hindered. The coating with an AEI yields a higher amount of restored zinc during electrodeposition in comparison to an uncoated zinc electrode-applying an AEI coating increases the achievable cycle number by up to six times. We investigate the morphology of the cycled electrodes and derive thereby the needs for further material classes that might be employed in the confinement concept. This approach demonstrates the benefit of ion-selective coatings, allowing for the permeation of hydroxide ions but not of oxidized zinc species, a concept which improves rechargeable batteries with zinc anodes, such as zinc-oxygen batteries.

Functionalization of Ti-40Nb implant material with strontium by reactive sputtering.

BACKGROUND: Surface functionalization of orthopedic implants with pharmaceutically active agents is a modern approach to enhance osseointegration in systemically altered bone. A local release of strontium, a verified bone building therapeutic agent, at the fracture site would diminish side effects, which could occur otherwise by oral administration. Strontium surface functionalization of specially designed titanium-niobium (Ti-40Nb) implant alloy would provide an advanced implant system that is mechanically adapted to altered bone with the ability to stimulate bone formation. METHODS: Strontium-containing coatings were prepared by reactive sputtering of strontium chloride (SrCl2) in a self-constructed capacitively coupled radio frequency (RF) plasma reactor. Film morphology, structure and composition were investigated by scanning electron microscopy (SEM), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) was used for the investigation of thickness and growth direction of the product layer. TEM lamellae were prepared using the focused ion beam (FIB) technique. Bioactivity of the surface coatings was tested by cultivation of primary human osteoblasts and subsequent analysis of cell morphology, viability, proliferation and differentiation. The results are correlated with the amount of strontium that is released from the coating in biomedical buffer solution, quantified by inductively coupled plasma mass spectrometry (ICP-MS). RESULTS: Dense coatings, consisting of SrOxCly, of more than 100 nm thickness and columnar structure, were prepared. TEM images of cross sections clearly show an incoherent but well-structured interface between coating and substrate without any cracks. Sr2+ is released from the SrOxCly coating into physiological solution as proven by ICP-MS analysis. Cell culture studies showed excellent biocompatibility of the functionalized alloy. CONCLUSIONS: Ti-40Nb alloy, a potential orthopedic implant material for osteoporosis patients, could be successfully plasma coated with a dense SrOxCly film. The material performed well in in vitro tests. Nevertheless, the Sr2+ release must be optimized in future work to meet the requirements of an effective drug delivery system.

Interfacial Reactivity Benchmarking of the Sodium Ion Conductors Na3PS4 and Sodium ß-Alumina for Protected Sodium Metal Anodes and Sodium All-Solid-State Batteries.

The interfacial stability of solid electrolytes at the electrodes is crucial for an application of all-solid-state batteries and protected electrodes. For instance, undesired reactions between sodium metal electrodes and the solid electrolyte form charge transfer hindering interphases. Due to the resulting large interfacial resistance, the charge transfer kinetics are altered and the overvoltage increases, making the interfacial stability of electrolytes the limiting factor in these systems. Driven by the promising ionic conductivities of Na3PS4, here we explore the stability and viability of Na3PS4 as a solid electrolyte against metallic Na and compare it to that of Na-ß″-Al2O3 (sodium ß-alumina). As expected, Na-ß″-Al2O3 is stable against sodium, whereas Na3PS4 decomposes with an increasing overall resistance, making Na-ß″-Al2O3 the electrolyte of choice for protected sodium anodes and all-solid-state batteries.

A comprehensive study on the cell chemistry of the sodium superoxide (NaO2) battery.

This work reports on the cell chemistry of a room temperature sodium-oxygen battery using an electrolyte of diethylene glycol dimethyl ether (diglyme) and sodium trifluoromethanesulfonate (NaSO3CF3, sodium triflate). Different from lithium-oxygen cells, where lithium peroxide is found as the discharge product, sodium superoxide (NaO2) is formed in the present cell, with overpotentials as low as 100 mV during charging. Several analytical methods are used to follow the cell reaction during discharge and charge. Changes in structure and morphology are studied by SEM and XRD. It is found that NaO2 grows as cubic particles with feed sizes in the range of 10-50 µm; upon recharge the particles consecutively decompose. Pressure monitoring during galvanostatic cycling shows that the coulombic efficiency (e(-)/O2) for discharge and charge is approx. 1.0, the expected value for NaO2 formation. Also optical spectroscopy is identified as a convenient and useful tool to follow the discharge-charge process. The maximum discharge capacity is found to be limited by oxygen transport within the electrolyte soaked carbon fiber cathode and pore blocking near the oxygen interface is observed. Finally electrolyte decomposition and sodium dendrite growth are identified as possible reasons for the limited capacity retention of the cell. The occurrence of undesired side reactions is analyzed by DEMS measurements during cycling as well as by post mortem XPS investigations.

Defect chemistry of oxide nanomaterials with high surface area: ordered mesoporous thin films of the oxygen storage catalyst CeO2-ZrO2.

Herein we report the electrical transport properties of a series of ordered mesoporous ceria-zirconia (CexZr1-xO2, referred to as mp-CZO) thin films with both a cubic structure of (17±2) nm diameter pores and nanocrystalline walls. Samples over the whole range of composition, including bare CeO2 and ZrO2, were fabricated by templating strategies using the large diblock copolymer KLE as the structure-directing agent. Both the nanoscale structure and the chemical composition of the mesoporous materials were analyzed by a combination of scanning and transmission electron microscopy, grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The total conductivity as a function of the film composition, temperature, and oxygen partial pressure was measured using impedance spectroscopy. The mesoporous solid solutions of CeO2-ZrO2 prepared in this work showed a higher stability against thermal ripening than both binary oxides, making them ideal model systems to study both the charge transport properties and the oxygen storage at elevated temperatures. We find that the redox properties of nanocrystalline mp-CZO thin films differ significantly from those of bulk CZO materials reported in the literature and, therefore, propose a defect chemical model of surface regions.