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Metastable nanostructures are kinetically trapped in local energy minima featuring intriguing surface and material properties. To unleash their potential, there is a need for non-equilibrium processes capable of stabilizing a large range of crystal phases outside thermodynamic equilibrium conditions by closely and flexibly controlling atomic reactant composition, spatial temperature distribution and residence time. Here, the capture of metastable pseudo-binary metal oxides at room temperature is demonstrated with scalable combustion-aerosol processes. By a combination of X-ray diffraction, electron microscopy and on-line flame characterization, the occurrence of metastable CoCu 2 O 3 is investigated with controlled crystal size (4-16 nm) over thermodynamically stable CuO and Co 3 O 4 . Immediate practical impact is demonstrated by exceptional sensing and stable catalytic performance for air pollutant detection (e.g., 15 parts-per-billion benzene) shown for, at least, 21 days. This approach can be extended to various binary, ternary and high entropy oxides with even more components. Also, secondary phases can be loaded on such metastable nanocrystals to access novel materials promising for actuators, energy storage or solar cells., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Platinum single atoms anchored onto activated carbon enable highly stable Hg-free synthesis of vinyl chloride (VCM) via acetylene hydrochlorination. Compared to gold-based alternatives, platinum catalysts are in initial phases of development. Most synthetic approaches rely on chloroplatinic acid, presenting opportunities to explore other precursors and their impact on catalyst structure, reactivity, and toxicity aspects. Here, we synthesize platinum single atom catalysts (Pt SACs, 0.2-0.8 wt % Pt) employing diverse Pt 2+ and Pt 4+ complexes with ammine, hydroxyl, nitrate, and chloride ligands, following a scalable impregnation protocol on activated carbon extrudates. X-ray absorption spectroscopy (XAS) reveals that Pt 4+ species reduce to Pt 2+ upon deposition onto the support. Despite similar oxidation states, the initial activity is precursor dependent, with tetraammine-derived Pt SACs displaying 2-fold higher VCM yield than chlorinated counterparts, linked to superior hydrogen chloride binding abilities by density functional theory (DFT) simulations. Their activity gradually converges due to dynamic active site restructuring, delivering remarkable precursor-independent stability over 150 h. Operando XAS and DFT studies uncover reaction-induced ligand exchange, generating common active and stable Pt-Cl x ( x = 2-3) species. Convergent active site evolution enables flexibility in metal precursor selection and thus toxicity minimization through multiparameter assessment. This study advances safe-by-design catalysts for VCM synthesis, highlighting the importance of toxicity analyses in early-stage catalyst development programs., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Sensors that can accurately assess oxygen (O 2 ) concentrations in real time are crucial for a wide range of applications spanning personal health monitoring, environmental protection, and industrial process development. Here a high-performance chemiresistive sensor that allows for the rapid detection of O 2 at room temperature under visible light illumination is described. Inspired by the operating principles of dye-sensitized solar cells, the chemiresistor is based on a single-walled carbon nanotube-titania hybrid (SWCNT-TiO 2 ) bearing a molecular Re-based photosensitizer [( P bpy)(CO) 3 ReBr] ( P bpy = 4,4'-[P(O)(OH) 2 ] 2 -2,2'-bipyridine). The resulting SWCNT-TiO 2 -Re composite undergoes photoinduced charge transfer that is sensitive to ppb levels of O 2 , thereby yielding a rapid and reversible chemiresistive response. Owing to its unique mode of operation and robust components, the sensor shows a high degree of selectivity for O 2 over a range of interferants, humidity tolerance, and multimonth benchtop stability. The approach presented herein demonstrates the translatability of concepts in light harvesting to the development of robust, rapid, and low-power sensing technologies., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Single-atom catalysts (SACs), possessing a uniform metal site structure, are a promising class of materials for selective oxidations of hydrocarbons. However, their design for targeted applications requires careful choice of metal-host combinations and suitable synthetic techniques. Here, we report iron atoms stabilised on defective hexagonal boron nitride (h-BN) via mechanochemical activation in a ball mill as an effective catalyst for propylene production via N 2 O-mediated oxidative propane dehydrogenation (N 2 O-ODHP), reaching 95% selectivity at 6% propane conversion and maintaining stable performance for 40 h on stream. This solvent-free synthesis allows simultaneous carrier exfoliation and surface defect generation, creating anchoring sites for catalytically-active iron atoms. The incorporation of a small metal quantity (0.5 wt%) predominantly generates a mix of atomically-dispersed Fe 2+ and Fe 3+ species, as confirmed by combining advanced microscopy and electron paramagnetic resonance, UV-vis and X-ray photoelectron spectroscopy analyses. Single-atom iron favours selective propylene formation, while metal oxide nanoparticles yield large quantities of CO x and cracking by-products. The lack of acidic functionalities on h-BN, hindering coke formation, and firm stabilisation of Fe sites, preventing metal sintering, ensure stable operation. These findings showcase N 2 O-ODHP as a promising propylene production technology and foster wider adoption of mechanochemical activation as a viable method for SACs synthesis., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Broadening the scope of functionalities that can be covalently bound to single-walled carbon nanotubes (SWCNTs) is crucial for enhancing the versatility of this promising nanomaterial class in applied settings. Here we report the covalent linkage of triphenylphosphine oxide [Ph 3 P(O)] to SWCNTs, a hitherto overlooked surface functionality. We detail the synthesis and structural characterization of a new family of phosphine oxide-functionalized diaryliodonium salts that can facilitate direct Ph 3 P(O) transfer and afford novel SWCNTs with tunable Ph 3 P(O) content (SWCNT-P). The molecularly-distributed and robust nature of the covalent Ph 3 P(O) attachment in SWCNT-P was supported by a combination of characterization methods including Raman, infrared, UV/Vis-NIR and X-ray photoelectron spectroscopies coupled with thermogravimetric analysis. Electron microscopy further revealed the effectiveness of the Ph 3 P(O) moiety for de-bundling SWCNTs to yield SWCNT-P with superior dispersibility and processability. Finally, electrochemical studies established that SWCNT-P is sensitive to the presence of Li + , Na + and K + wherein the Gutmann-Beckett Lewis acidity parameters of the ions were quantitatively transduced by Ph 3 P(O) to electrochemical responses. This work hence presents a synthetic, structural, spectroscopic and electrochemical foundation for a new phosphorus-enriched responsive nanomaterial platform featuring the Ph 3 P(O) functionality., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Metal promotion could unlock high performance in zinc-zirconium catalysts, ZnZrO x , for CO 2 hydrogenation to methanol. Still, with most efforts devoted to costly palladium, the optimal metal choice and necessary atomic-level architecture remain unclear. Herein, we investigate the promotion of ZnZrO x catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) prepared via a standardized flame spray pyrolysis approach. Cu emerges as the most effective promoter, doubling methanol productivity. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses and density functional theory simulations reveal that Cu 0 species form Zn-rich low-nuclearity CuZn clusters on the ZrO 2 surface during reaction, which correlates with the generation of oxygen vacancies in their vicinity. Mechanistic studies demonstrate that this catalytic ensemble promotes the rapid hydrogenation of intermediate formate into methanol while effectively suppressing CO production, showcasing the potential of low-nuclearity metal ensembles in CO 2 -based methanol synthesis., (© 2024. The Author(s).)

Designing reactive surface clusters at the nanoscale on metal-oxide supports enables selective molecular interactions in low-temperature catalysis and chemical sensing. Yet, finding effective material combinations and identifying the reactive site remains challenging and an obstacle for rational catalyst/sensor design. Here, the low-temperature oxidation of formaldehyde with CuO x clusters on Co 3 O 4 nanoparticles is demonstrated yielding an excellent sensor for this critical air pollutant. When fabricated by flame-aerosol technology, such CuO x clusters are finely dispersed, while some Cu ions are incorporated into the Co 3 O 4 lattice enhancing thermal stability. Importantly, infrared spectroscopy of adsorbed CO, near edge X-ray absorption fine structure spectroscopy and temperature-programmed reduction in H 2 identified Cu + and Cu 2+ species in these clusters as active sites. Remarkably, the Cu + surface concentration correlated with the apparent activation energy of formaldehyde oxidation (Spearman's coefficient ρ = 0.89) and sensor response (0.96), rendering it a performance descriptor. At optimal composition, such sensors detected even the lowest formaldehyde levels of 3 parts-per-billion (ppb) at 75°C, superior to state-of-the-art sensors. Also, selectivity to other aldehydes, ketones, alcohols, and inorganic compounds, robustness to humidity and stable performance over 4 weeks are achieved, rendering such sensors promising as gas detectors in health monitoring, air and food quality control., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Pyrochlore-type iron (III) hydroxy fluorides (Pyr-IHF) are appealing low-cost stationary energy storage materials due to the virtually unlimited supply of their constituent elements, their high energy densities, and fast Li-ion diffusion. However, the prohibitively high costs of synthesis and cathode architecture currently prevent their commercial use in low-cost Li-ion batteries. Herein, a facile and cost-effective dissolution-precipitation synthesis of Pyr-IHF from soluble iron (III) fluoride precursors is presented. High capacity retention by synthesized Pyr-IHF of >80% after 600 cycles at a high current density of 1 A g -1 is obtained, without elaborate electrode engineering. Operando synchrotron X-ray diffraction guides the selective synthesis of Pyr-IHF such that different water contents can be tested for their effect on the rate capability. Li-ion diffusion is found to occur in the 3D hexagonal channels of Pyr-IHF, formed by corner-sharing FeF 6-x (OH) x octahedra., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

The development of selective catalysts for direct conversion of ammonia into nitrous oxide, N 2 O, will circumvent the conventional five-step manufacturing process and enable its wider utilization in oxidation catalysis. Deviating from commonly accepted catalyst design principles for this reaction, reliant on manganese oxide, we herein report an efficient system comprised of isolated chromium atoms (1 wt %) stabilized in the ceria lattice by coprecipitation. The latter, in contrast to a simple impregnation approach, ensures firm metal anchoring and results in stable and selective N 2 O production over 100 h on stream up to 79% N 2 O selectivity at full NH 3 conversion. Raman, electron paramagnetic resonance, and in situ UV-vis spectroscopies reveal that chromium incorporation enhances the density of oxygen vacancies and the rate of their generation and healing. Accordingly, temporal analysis of products, kinetic studies, and atomistic simulations show lattice oxygen of ceria to directly participate in the reaction, establishing the cocatalytic role of the carrier. Coupled with the dynamic restructuring of chromium sites to stabilize intermediates of N 2 O formation, these factors enable catalytic performance on par with or exceeding benchmark systems. These findings demonstrate how nanoscale engineering can elevate a previously overlooked metal into a highly competitive catalyst for selective ammonia oxidation to N 2 O, paving the way toward industrial implementation., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Carbon supports are ubiquitous components of heterogeneous catalysts for acetylene hydrochlorination to vinyl chloride, from commercial mercury-based systems to more sustainable metal single-atom alternatives. Their potential co-catalytic role has long been postulated but never unequivocally demonstrated. Herein, we evidence the bifunctionality of carbons and metal sites in the acetylene hydrochlorination catalytic cycle. Combining operando X-ray absorption spectroscopy with other spectroscopic and kinetic analyses, we monitor the structure of single metal atoms (Pt, Au, Ru) and carbon supports (activated, non-activated, and nitrogen-doped) from catalyst synthesis, using various procedures, to operation at different conditions. Metal atoms exclusively activate hydrogen chloride, while metal-neighboring sites in the support bind acetylene. Resolving the coordination environment of working metal atoms guides theoretical simulations in proposing potential binding sites for acetylene in the support and a viable reaction profile. Expanding from single-atom to ensemble catalysis, these results reinforce the importance of optimizing both metal and support components to leverage the distinct functions of each for advancing catalyst design., (© 2023. Springer Nature Limited.)

Nitrous oxide, N 2 O, exhibits unique reactivity in oxidation catalysis, but the high manufacturing costs limit its prospective uses. Direct oxidation of ammonia, NH 3 , to N 2 O can ameliorate this issue but its implementation is thwarted by suboptimal catalyst selectivity and stability, and the lack of established structure-performance relationships. Systematic and controlled material nanostructuring offers an innovative approach for advancement in catalyst design. Herein low-valent manganese atoms stabilized on ceria, CeO 2 , are discovered as the first stable catalyst for NH 3 oxidation to N 2 O, exhibiting two-fold higher productivity than the state-of-the-art. Detailed mechanistic, computational and kinetic studies reveal CeO 2 as the mediator of oxygen supply, while undercoordinated manganese species activate O 2 and facilitate N 2 O evolution via NN bond formation between nitroxyl, HNO, intermediates. Synthesis via simple impregnation of a small metal quantity (1 wt%) predominantly generates isolated manganese sites, while full atomic dispersion is achieved upon redispersion of sporadic oxide nanoparticles during reaction, as confirmed by advanced microscopic analysis and electron paramagnetic resonance spectroscopy. Subsequently, manganese speciation is maintained, and no deactivation is observed over 70 h on stream. CeO 2 -supported isolated transition metals emerge as a novel class of materials for N 2 O production, encouraging future studies to evaluate their potential in selective catalytic oxidations at large., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Operando X-ray absorption spectroscopy identified that the concentration of Fe 2+ species in the working state-of-the-art Pt-FeO x catalysts quantitatively correlates to their preferential carbon monoxide oxidation steady-state reaction rate at ambient temperature. Deactivation of such catalysts with time on stream originates from irreversible oxidation of active Fe 2+ sites. The active Fe 2+ species are presumably Fe +2 O -2 clusters in contact with platinum nanoparticles; they coexist with spectator trivalent oxidic iron (Fe 3+ ) and metallic iron (Fe 0 ) partially alloyed with platinum. The concentration of active sites and, therefore, the catalyst activity strongly depends on the pretreatment conditions. Fe 2+ is the resting state of the active sites in the preferential carbon monoxide oxidation cycle., (© 2022 Wiley-VCH GmbH.)

Laboratory-based X-ray absorption spectroscopy (XAS) and especially X-ray absorption near-edge structure (XANES) offers new opportunities in catalyst characterization and presents not only an alternative, but also a complementary approach to precious beamtime at synchrotron facilities. We successfully designed a laboratory-based setup for performing operando, quasi-simultaneous XANES analysis at multiple K-edges, more specifically, operando XANES of mono-, bi-, and trimetallic CO 2 hydrogenation catalysts containing Ni, Fe, and Cu. Detailed operando XANES studies of the multielement solid catalysts revealed metal-dependent differences in the reducibility and re-oxidation behavior and their influence on the catalytic performance in CO 2 hydrogenation. The applicability of operando laboratory-based XANES at multiple K-edges paves the way for advanced multielement catalyst characterization complementing detailed studies at synchrotron facilities., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Tuning the transition dipole moment (TDM) orientation in low-dimensional semiconductors is of fundamental and practical interest, as it enables high-efficiency nanophotonics and light-emitting diodes. However, despite recent progress in nanomaterials physics and chemistry, material systems that allow continuous tuning of the TDM orientation remain rare. Here, combining k -space photoluminescence spectroscopy and multiscale modeling, we demonstrate that the TDM orientation in lead halide perovskite (LHP) nanoplatelet (NPL) solids is largely confinement-tunable through the NPL geometry that regulates the anisotropy of Bloch states, dielectric confinement, and exciton fine structure. We further quantified the role of uniaxial ordering during NPL assembly in modifying the macroscopic emission directionality of thin films, which is especially important in actual optoelectronic devices. Our theoretical framework successfully corroborates the previous prediction of exciton bright level order reversal with experimental evidence of a counterintuitive reduction of in-plane dipole ratio in ultrathin (one- and two-monolayer-thick) NPLs, even at room temperature. More interestingly, the NPLs retain their TDM orientation in binary blends irrespective of interparticle energy transfer, owing to the phase segregation and NPL-NPL decoupling, enabling the design of films whose fluorescence exhibits an intrinsic angle-dependent color gradient.

Controlling the precise atomic architecture of supported metals is central to optimizing their catalytic performance, as recently exemplified for nanostructured platinum and ruthenium systems in acetylene hydrochlorination, a key process for vinyl chloride production. This opens the possibility of building on historically established activity correlations. In this study, we derived quantitative activity, selectivity and stability descriptors that account for the metal-dependent speciation and host effects observed in acetylene hydrochlorination. To achieve this, we generated a platform of Au, Pt, Ru, Ir, Rh and Pd single atoms and nanoparticles supported on different types of carbon and assessed their evolution during synthesis and under the relevant reaction conditions. Combining kinetic, transient and chemisorption analyses with modelling, we identified the acetylene adsorption energy as a speciation-sensitive activity descriptor, further determining catalyst selectivity with respect to coke formation. The stability of the different nanostructures is governed by the interplay between single atom-support interactions and chlorine affinity, promoting metal redispersion or agglomeration, respectively., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

The production of nitrous oxide, N 2 O, via NH 3 oxidation is not on a practical scale due to the lack of a suitable catalyst. Instead, it is produced via thermal decomposition of NH 4 NO 3 , rendering N 2 O too costly and limiting its prospective uses. Herein, we report CeO 2 -supported Au nanoparticles (2-3 nm) as a highly selective catalyst for low-temperature NH 3 oxidation to N 2 O, exhibiting two orders of magnitude higher space-time yield than the state-of-the-art Mn-Bi/α-Al 2 O 3 and remarkable stability over 70 h on stream. The reaction proceeds via a Mars-van Krevelen mechanism, with the density of interfacial Au δ+ species and the oxygen storage capacity of CeO 2 identified as the key performance descriptors. The latter could be enhanced by cobalt doping, improving the catalytic activity and setting a new benchmark for N 2 O productivity. These findings establish NH 3 oxidation as an efficient process for N 2 O manufacture and facilitate its broader utilization in selective oxidations., (© 2022 Wiley-VCH GmbH.)

Quantum dot (QD) light-emitting diodes (LEDs) are emerging as one of the most promising candidates for next-generation displays. However, their intrinsic light outcoupling efficiency remains considerably lower than the organic counterpart, because it is not yet possible to control the transition-dipole-moment (TDM) orientation in QD solids at device level. Here, using the colloidal lead halide perovskite anisotropic nanocrystals (ANCs) as a model system, we report a directed self-assembly approach to form the anisotropic nanocrystal superlattices (ANSLs). Emission polarization in individual ANCs rescales the radiation from horizontal and vertical transition dipoles, effectively resulting in preferentially horizontal TDM orientation. Based on the emissive thin films comprised of ANSLs, we demonstrate an enhanced ratio of horizontal dipole up to 0.75, enhancing the theoretical light outcoupling efficiency of greater than 30%. Our optimized single-junction QD LEDs showed peak external quantum efficiency of up to 24.96%, comparable to state-of-the-art organic LEDs., (© 2022. The Author(s).)

Many in-memory computing frameworks demand electronic devices with specific switching characteristics to achieve the desired level of computational complexity. Existing memristive devices cannot be reconfigured to meet the diverse volatile and non-volatile switching requirements, and hence rely on tailored material designs specific to the targeted application, limiting their universality. "Reconfigurable memristors" that combine both ionic diffusive and drift mechanisms could address these limitations, but they remain elusive. Here we present a reconfigurable halide perovskite nanocrystal memristor that achieves on-demand switching between diffusive/volatile and drift/non-volatile modes by controllable electrochemical reactions. Judicious selection of the perovskite nanocrystals and organic capping ligands enable state-of-the-art endurance performances in both modes - volatile (2 × 10 6 cycles) and non-volatile (5.6 × 10 3 cycles). We demonstrate the relevance of such proof-of-concept perovskite devices on a benchmark reservoir network with volatile recurrent and non-volatile readout layers based on 19,900 measurements across 25 dynamically-configured devices., (© 2022. The Author(s).)

Colloidal metal halide perovskite (MHP) nanocrystals (NCs) are an emerging class of fluorescent quantum dots (QDs) for next-generation optoelectronics. A great hurdle hindering practical applications, however, is their high lead content, where most attempts addressing the challenge in the literature compromised the material's optical performance or colloidal stability. Here, we present a postsynthetic approach that stabilizes the lead-reduced MHP NCs through high-entropy alloying. Upon doping the NCs with multiple elements in considerably high concentrations, the resulting high-entropy perovskite (HEP) NCs remain to possess excellent colloidal stability and narrowband emission, with even higher photoluminescence (PL) quantum yields, η PL , and shorter fluorescence lifetimes, τ PL . The formation of multiple phases containing mixed interstitial and doping phases is suggested by X-ray crystallography. Importantly, the crystalline phases with higher degrees of lattice expansion and lattice contraction can be stabilized upon high-entropy alloying. We show that the lead content can be approximately reduced by up to 55% upon high-entropy alloying. The findings reported here make one big step closer to the commercialization of perovskite NCs.

The introduction of a foreign metal atom in the coordination environment of single-atom catalysts constitutes an exciting frontier of active-site engineering, generating bimetallic low-nuclearity catalysts often exhibiting unique catalytic synergies. To date, the exploration of their full scope is thwarted by (i) the lack of synthetic techniques with control over intermetallic coordination, and (ii) the challenging characterization of these materials. Herein, carbon-host functionalization is presented as a strategy to selectively generate Au-Ru dimers and isolated sites by simple incipient wetness impregnation, as corroborated by careful X-ray absorption spectroscopy analysis. The distinct catalytic fingerprints are unveiled via the hydrogen evolution reaction, employed as a probe for proton adsorption properties. Intriguingly, the virtually inactive Au atoms enhance the reaction kinetics of their Ru counterparts already when spatially isolated, by shifting the proton adsorption free energy closer to neutrality. Remarkably, the effect is magnified by a factor of 2 in dimers. These results exemplify the relevance of controlling intermetallic coordination for the rational design of bimetallic low-nuclearity catalysts., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

The dinuclear Ru diazadiene olefin complex, [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ], is an active catalyst for hydrogen evolution in a Polymer Exchange Membrane (PEM) water electrolyser. When supported on high surface area carbon black and at 80 °C, [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ]@C evolves hydrogen at the cathode of a PEM electrolysis cell (400 mA cm -2 , 1.9 V). A remarkable turn over frequency (TOF) of 7800 mol H 2 mol catalyst -1 h -1 is maintained over 7 days of operation. A series of model reactions in homogeneous media and in electrochemical half cells, combined with DFT calculations, are used to rationalize the hydrogen evolution mechanism promoted by [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ]., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Towards enhancement of the energy density of Li-ion batteries, BiF 3 has recently attracted considerable attention as a compelling conversion-type cathode material due to its high theoretical capacity of 302 mAh g -1 , average discharge voltage of ca. 3.0 V vs. Li + /Li, the low theoretical volume change of ca. 1.7% upon lithiation, and an intrinsically high oxidative stability. Here we report a facile and scalable synthesis of phase-pure and highly crystalline orthorhombic BiF 3 via thermal decomposition of bismuth(III) trifluoroacetate at T = 300 °C under inert atmosphere. The electrochemical measurements of BiF 3 in both carbonate (LiPF 6 -EC/DMC)- and ionic liquid-based (LiFSI-Pyr 1,4 TFSI) Li-ion electrolytes demonstrated that ionic liquids improve the cyclic stability of BiF 3 . In particular, BiF 3 in 4.3 M LiFSI-Pyr 1,4 TFSI shows a high initial capacity of 208 mA g -1 and capacity retention of ca. 50% over at least 80 cycles at a current density of 30 mA g -1 ., (© 2022. The Author(s).)

Supported low-nuclearity metal catalysts integrating single atoms or small clusters have emerged as promising materials for diverse applications. While sophisticated synthetic methods provide a high level of nuclearity control in the subnanometre regime, these routes do not fulfil the requirements for translation into industrial practice of (i) effectiveness for high metal contents and (ii) facile scalability. Herein, we present a gas-phase redispersion strategy consisting of sequential C 2 H 2 and HCl treatments to gradually disperse Ru, Rh and Ir nanoparticles supported on commercial activated carbon with metal content up to 10 wt% and initial average sizes of ≈ 1 nm into small clusters and eventually single atoms. Avoidance of nanoparticle surface overchlorination, which hinders C 2 H 2 adsorption, is identified as key for the redispersion process, as demonstrated by the inefficacy of both C 2 H 2 -HCl cofeeding and inverse sequence ( i.e ., HCl first) treatments. Precise size control (±0.1 nm) is enabled by regulating the number of C 2 H 2 -HCl cycles. Detailed characterisation by X-ray absorption spectroscopy, electron paramagnetic resonance and time-resolved mass spectrometry reveals that the redispersion occurs via a layer-by-layer mechanism. Specifically, the migration of surface chlorinated metal species to the carbon support is induced by the C 2 H 2 treatment, depleting accessible surface Cl atoms, while the subsequent HCl treatment rechlorinates the cluster surface. The strategy paves the way for the generation of high-density metal sites with tuneable nuclearity for tailored applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Pd/ZnO catalysts show good activity and high selectivity to methanol during catalytic CO 2 hydrogenation. The Pd-Zn alloy phase has usually been considered as the active phase, though mechanistic studies under operando conditions have not been conducted to verify this. Here, we report a mechanistic study under realistic conditions of methanol synthesis, using in situ and operando X-ray absorption spectroscopy, X-ray powder diffraction, and time-resolved isotope labeling experiments coupled with FTIR spectroscopy and mass spectrometry. Pd-Zn alloy-based catalysts, prepared through reduction of a heterobimetallic Pd II Zn II acetate bridge complex, and which do not contain zinc oxide or any PdZn/ZnO interface, produce mostly CO. The Pd-Zn phase is associated with the formation of CO, and does not provide the active sites required to produce methanol from the direct hydrogenation of carbon dioxide. The presence of a ZnO phase, in contact with a Pd-Zn phase, is essential for efficient methanol production., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

For decades, carbons have been the support of choice in acetylene hydrochlorination, a key industrial process for polyvinyl chloride manufacture. However, no unequivocal design criteria could be established to date, due to the complex interplay between the carbon host and the metal nanostructure. Herein, we disentangle the roles of carbon in determining activity and stability of platinum-, ruthenium-, and gold-based hydrochlorination catalysts and derive descriptors for optimal host design, by systematically varying the porous properties and surface functionalization of carbon, while preserving the active metal sites. The acetylene adsorption capacity is identified as central activity descriptor, while the density of acidic oxygen sites determines the coking tendency and thus catalyst stability. With this understanding, a platinum single-atom catalyst is developed with stable catalytic performance under two-fold accelerated deactivation conditions compared to the state-of-the-art system, marking a step ahead towards sustainable PVC production.

The performance of functional materials is either driven or limited by nanoscopic heterogeneities distributed throughout the material's volume. To better our understanding of these materials, we need characterization tools that allow us to determine the nature and distribution of these heterogeneities in their native geometry in 3D. Here, we introduce a method based on x-ray near-edge spectroscopy, ptychographic x-ray computed nanotomography, and sparsity techniques. The method allows the acquisition of quantitative multimodal tomograms of representative sample volumes at sub-30 nm half-period spatial resolution within practical acquisition times, which enables local structure refinements in complex geometries. To demonstrate the method's capabilities, we investigated the transformation of vanadium phosphorus oxide catalysts with industrial use. We observe changes from the micrometer to the atomic level and the formation of a location-specific defect so far only theorized. These results led to a reevaluation of these catalysts used in the production of plastics., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

Pt-group metal (PGM)-free catalysts of the Me-N-C type based on abundant and inexpensive elements have gained importance in the field of oxygen reduction reaction (ORR) electrocatalysis due to their promising ORR-activities. Their insufficient stability, however, has fueled the interest in obtaining an in-depth understanding of their composition, which requires highly sensitive techniques compatible with their low metal contents (typically <5 wt%). In the particular context of iron-based materials, 57Fe-Mössbauer spectroscopy is often used to provide such compositional information, but requires (partially) 57Fe-enriched precursors. As a consequence, the extrapolation of conclusions drawn from Mössbauer measurements on 57Fe-enriched catalysts to equivalent materials with the standard isotope distribution relies on the assumption that the metal precursor's isotopic profile does not affect the catalysts' composition and ORR-activity. To verify this hypothesis, in this study we prepared two series of Fe-based catalysts using distinctively different synthesis approaches and various relative contents of 57Fe-enriched precursors, and observed that the extent of the latter parameter significantly affected the catalysts' ORR-activity. This effect was successfully correlated with the Fe-speciation of the catalysts inferred from the characterization of these samples with Mössbauer and X-ray absorption spectroscopies. Ultimately, these results highlight the crucial importance of verifying the consistency of the catalysts' activity and composition upon comparing standard and 57Fe-enriched samples.

Deep-tissue fluorescence imaging remains a major challenge as there is limited availability of bright biocompatible materials with high photo- and chemical stability. Contrast agents with emission wavelengths above 1000 nm are most favorable for deep tissue imaging, offering deeper penetration and less scattering than those operating at shorter wavelengths. Organic fluorophores suffer from low stability while inorganic nanomaterials (e.g. quantum dots) are based typically on heavy metals raising toxicity concerns. Here, we report scalable flame aerosol synthesis of water-dispersible Ba 3 (VO 4 ) 2 nanoparticles doped with Mn 5+ which exhibit a narrow emission band at 1180 nm upon near-infrared excitation. Their co-synthesis with Bi 2 O 3 results in even higher absorption and ten-fold increased emission intensity. The addition of Bi 2 O 3 also improved both chemical stability and cytocompatibility by an order of magnitude enabling imaging deep within tissue. Taken together, these bright particles offer excellent photo-, chemical and colloidal stability in various media with cytocompatibility to HeLa cells superior to existing commercial contrast agents.

The electroreduction of carbon dioxide is considered a key reaction for the valorization of CO 2 emitted in industrial processes or even present in the environment. Cobalt-nitrogen co-doped carbon materials featuring atomically dispersed Co-N sites have been shown to display superior activities and selectivities for the reduction of carbon dioxide to CO, which, in combination with H 2 (i.e., as syngas), is regarded as an added-value CO 2 -reduction product. Such catalysts can be synthesized using heat treatment steps that imply the carbonization of Co-N-containing precursors, but the detailed effects of the synthesis conditions and corresponding materials' composition on their catalytic activities have not been rigorously studied. To this end, in the present work, we synthesized cobalt-nitrogen co-doped carbon materials with different heat treatment temperatures and studied the relation among their surface- and Co-speciation and their CO 2 -to-CO electroreduction activity. Our results reveal that atomically dispersed cobalt-nitrogen sites are responsible for CO generation while suggesting that this CO-selectivity improves when these atomic Co-N centers are hosted in the carbon layers that cover the Co nanoparticles featured in the catalysts synthesized at higher heat treatment temperatures.

Gold single-atom catalysts (SACs) exhibit outstanding reactivity in acetylene hydrochlorination to vinyl chloride, but their practical applicability is compromised by current synthesis protocols, using aqua regia as chlorine-based dispersing agent, and their high susceptibility to sintering on non-functionalized carbon supports at >500 K and/or under reaction conditions. Herein, a sustainable synthesis route to carbon-supported gold nanostructures in bimetallic catalysts is developed by employing salts as alternative chlorine source, allowing for tailored gold dispersion, ultimately reaching atomic level when using H 2 PtCl 6 . To rationalize these observations, several synthesis parameters (i.e., pH, Cl-content) as well as the choice of metal chlorides are evaluated, hinting at the key role of platinum in promoting a chlorine-mediated dispersion mechanism. This can be further extrapolated to redisperse large gold agglomerates (>70 nm) on carbon carriers into isolated atoms, which has important implications for catalyst regeneration. Another key role of platinum single atoms is to inhibit the sintering of their spatially isolated gold-based analogs up to 800 K and during acetylene hydrochlorination, without compromising the intrinsic activity of Au(I)-Cl active sites. Accordingly, exploiting cooperativity effects of a second metal is a promising strategy towards practical applicability of gold SACs, opening up exciting opportunities for multifunctional single-atom catalysis., (© 2021 Wiley-VCH GmbH.)

Colloidal nanocrystals (NCs) of lead halide perovskites have generated considerable interest in the fabrication of optoelectronic devices, such as light emitting-diodes (LEDs), because of their tunable optical bandgap, narrow spectral width, and high defect tolerance. However, the inhomogeneous halide distribution within individual NCs remains a critical challenge in order to obtain color-stable electroluminescence in mixed-halide systems. Here, we demonstrate a new post-synthetic approach, ligand-assisted solid phase synthesis (LASPS), for the preparation of electroluminescent colloidal NCs of methylammonium (MA) lead halide perovskites, at room temperature. The slow reaction kinetics preserves the morphology, size, and shape in the resulting NCs whose emission covers the entire visible spectral region with photoluminescence (PL) quantum yields (QYs) of up to >90% and colloidal stability up to several months. The LEDs fabricated using the prepared mixed-halide NCs display narrowband electroluminescence (EL) ranging from 476 to 720 nm. The optimized red LEDs exhibit an external quantum efficiency, η ext , of up to 2.65%, with the CIE 1931 color coordinates of (0.705, 0.290), nearly identical to those of the red primary in the recommendation (rec.) 2020 standard (0.708, 0.292)., Competing Interests: The authors declare that they have no other competing interests., (This journal is © The Royal Society of Chemistry.)

Chemical modifiers enhance the efficiency of metal catalysts in numerous applications, but their introduction often involves toxic or expensive precursors and complicates the synthesis. Here, we show that a porous boron nitride carrier can directly modify supported palladium nanoparticles, originating unparalleled performance in the continuous semi-hydrogenation of alkynes. Analysis of the impact of various structural parameters reveals that using a defective high surface area boron nitride and ensuring a palladium particle size of 4-5 nm is critical for maximizing the specific rate. The combined experimental and theoretical analyses point towards boron incorporation from defects in the support to the palladium subsurface, creating the desired isolated ensembles determining the selectivity. This practical approach highlights the unexplored potential of using tailored carriers for catalyst design., (© 2020 Wiley-VCH GmbH.)

Hydrodesulphurization, the removal of sulphur from crude oils, is an essential catalytic process in the petroleum industry safeguarding the production of clean hydrocarbons. Sulphur removal is critical for the functionality of downstream processes and vital to the elimination of environmental pollutants. The effectiveness of such an endeavour is among other factors determined by the structural arrangement of the heterogeneous catalyst. Namely, the accessibility of the catalytically active molybdenum disulphide (MoS 2 ) slabs located on the surfaces of a porous alumina carrier. Here, we examined a series of pristine sulfided Mo and NiMo hydrodesulphurization catalysts of increasing metal loading prepared on commercial alumina carriers using ptychographic X-ray computed nanotomography. Structural analysis revealed a build consisting of two interwoven support matrix elements differing in nanoporosity. With increasing metal loading, approaching that of industrial catalysts, these matrix elements exhibit a progressively dissimilar MoS 2 surface coverage as well as MoS 2 cluster formation at the matrix element boundaries. This is suggestive of metal deposition limitations and/ or catalyst activation and following prohibitive of optimal catalytic utilization. These results will allow for diffusivity calculations, a better rationale of current generation catalyst performance as well as a better distribution of the active phase in next-generation hydrodesulphurization catalysts., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Acetone is a toxic air pollutant and a key breath marker for non-invasively monitoring fat metabolism. Its routine detection in realistic gas mixtures (i.e., human breath and indoor air), however, is challenging, as low-cost acetone sensors suffer from insufficient selectivity. Here, a compact detector for acetone sensing is introduced, having unprecedented selectivity (>250) over the most challenging interferants (e.g., alcohols, aldehydes, aromatics, isoprene, ammonia, H 2 , and CO). That way, acetone is quantified with fast response (<1 min) down to, at least, 50 parts per billion (ppb) in gas mixtures with such interferants having up to two orders of magnitude higher concentration than acetone at realistic relative humidities (RH = 30-90%). The detector consists of a catalytic packed bed (30 mg) of flame-made Al 2 O 3 nanoparticles (120 m 2 g -1 ) decorated with Pt nanoclusters (average size 9 nm) and a highly sensitive chemo-resistive sensor made by flame aerosol deposition and in situ annealing of nanostructured Si-doped ε -WO 3 (Si/WO 3 ). Most importantly, the catalytic packed bed converts interferants continuously enabling highly selective acetone sensing even in the exhaled breath of a volunteer. The detector exhibits stable performance over, at least, 145 days at 90% RH, as validated by mass spectrometry., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Published by Wiley‐VCH GmbH.)

Silicon oxycarbide (SiOC) has recently regained attention in the field of Li-ion batteries, owing to its effectiveness as a host matrix for nanoscale anode materials alloying with Li. The SiOC matrix, itself providing a high Li-ion storage capacity of 600 mA h g-1, assists in buffering volumetric changes upon lithiation and largely suppresses the formation of an unstable solid-electrolyte interface. Herein, we present the synthesis of homogeneously embedded Sb nanoparticles in a SiOC matrix with the size of 5-40 nm via the pyrolysis of a preceramic polymer. The latter is obtained through the Pt-catalyzed gelation reaction of Sb 2-ethylhexanoate and a poly(methylhydrosiloxane)/divinylbenzene mixture. The complete miscibility of these precursors was achieved by the functionalization of poly(methylhydrosiloxane) with apolar divinyl benzene side-chains. We show that anodes composed of SiOC/Sb exhibit a high rate capability, delivering charge storage capacity in the range of 703-549 mA h g-1 at a current density of 74.4-2232 mA g-1. The impact of Sb on the Si-O-C bonding and on free carbon content of SiOC matrix, along with its concomitant influence on Li-ion storage capacity of SiOC was assessed by Raman and 29Si and 7Li solid-state NMR spectroscopies.

The assembly of protein and inorganic nanoparticles represents an attractive approach to generate composite materials with multiple functions. Herein, we functionalize inorganic nanoparticles with intrinsically disordered protein domains associated with the formation of membraneless compartments in cells. These protein sequences, defined as low complexity domains (LCDs), encode intermolecular interactions that drive highly controlled, dynamic self-assembly in response to environmental changes. We show that the properties of the LCDs can be transferred to inorganic nanoparticles, inducing controlled phase separation that is dynamic and responsive to ionic strength and pH. Specifically, we hybridize magnetic nanoparticles with multi-domain proteins consisting of LCD domains and a globular enzyme, generating dynamic protein-composite compartments that locally confine hybrid chemoenzymatic reactions and respond to external magnetic fields and changes in solution conditions., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In spite of numerous works in the field of chemical valorization of carbon dioxide into methanol, the nature of high activity of Cu/ZnO catalysts, including the reaction mechanism and the structure of the catalyst active site, remains the subject of intensive debate. By using high-pressure operando techniques: steady-state isotope transient kinetic analysis coupled with infrared spectroscopy, together with time-resolved X-ray absorption spectroscopy and X-ray powder diffraction, and supported by electron microscopy and theoretical modeling, we present direct evidence that zinc formate is the principal observable reactive intermediate, which in the presence of hydrogen converts into methanol. Our results indicate that the copper-zinc alloy undergoes oxidation under reaction conditions into zinc formate, zinc oxide and metallic copper. The intimate contact between zinc and copper phases facilitates zinc formate formation and its hydrogenation by hydrogen to methanol.

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO 2 is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO 2 with a very high surface area (>130 m 2 g -1 ) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO 2 are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPR-H 2 , and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s -1 and a mass activity higher than 370 A g -1 , which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm -2 at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO 2 , on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.

A worldwide replacement of the toxic mercuric chloride catalyst in vinyl chloride manufacture via acetylene hydrochlorination is slowed down by the limited durability of alternative catalytic systems at high space velocities. Here, we demonstrate that platinum single atoms on carbon carriers are substantially more stable (up to 1073 K) than their gold counterparts (up to 473 K), enabling facile and scalable preparation and precise tuning of their coordination environment by simple temperature control. By combining kinetic analysis, advanced characterisation, and density functional theory, we assess how the Pt species determines the catalytic performance and thereby identify Pt(II)-Cl as the active site, being three times more active than Pt nanoparticles. Remarkably, we show that Pt single atoms exhibit outstanding stability in acetylene hydrochlorination and surpass the space-time-yields of their gold-based analogues after 25 h time-on-stream, qualifying as candidate for sustainable vinyl chloride production., Competing Interests: Competing interests The authors declare that they have no competing interests.

Miniaturized photonic sources based on semiconducting two-dimensional (2D) materials offer new technological opportunities beyond the modern III-V platforms. For example, the quantum-confined 2D electronic structure aligns the exciton transition dipole moment parallel to the surface plane, thereby outcoupling more light to air which gives rise to high-efficiency quantum optics and electroluminescent devices. It requires scalable materials and processes to create the decoupled multi-quantum-well superlattices, in which individual 2D material layers are isolated by atomically thin quantum barriers. Here, we report decoupled multi-quantum-well superlattices comprised of the colloidal quantum wells of lead halide perovskites, with unprecedentedly ultrathin quantum barriers that screen interlayer interactions within the range of 6.5 Å. Crystallographic and 2D k-space spectroscopic analysis reveals that the transition dipole moment orientation of bright excitons in the superlattices is predominantly in-plane and independent of stacking layer and quantum barrier thickness, confirming interlayer decoupling.

ZSM-5 zeolites attract considerable attention owing to their wide range of applications in catalysis and separation. The crystals that are synthesized with tetrapropylammonium ions (TPA+) as the template show aluminum-zoning, i.e. aluminum being concentrated in the rim part of the crystal. Here, we study the aluminum distribution within individual crystals as a function of synthesis time and find that the degree of aluminum-zoning evolves. Crystals with inhomogeneous aluminum distribution persist since their emergence from the early stages of hydrothermal treatment. The degree of aluminum-zoning in the crystals increases with the synthesis time, accompanied by an increase in the crystal size and subsequently the formation of a well-defined crystal morphology. This indicates a gradual aluminum migration toward the crystal surface during the course of crystallization. Moreover, the addition of high-aluminum-containing species to the existing crystals preferentially takes place at the late stages of synthesis, which contributes to the inhomogeneous aluminum distribution within a crystal. As a result, the finally formed crystals have not only the largest crystal size but also the highest degree of aluminum-zoning. The insight into the origin of aluminum-zoning that our work provides advances our understanding of the relationship between aluminum distribution in zeolites and the synthesis time to design better catalysts.

Attaining thermodynamic stability of colloids in a broad range of concentrations has long been a major thrust in the field of colloidal ligand-capped semiconductor nanocrystals (NCs). This challenge is particularly pressing for the novel NCs of cesium lead halide perovskites (CsPbX 3 ; X = Cl, Br) owing to their highly dynamic and labile surfaces. Herein, we demonstrate that soy lecithin, a mass-produced natural phospholipid, serves as a tightly binding surface-capping ligand suited for a high-reaction yield synthesis of CsPbX 3 NCs (6-10 nm) and allowing for long-term retention of the colloidal and structural integrity of CsPbX 3 NCs in a broad range of concentrations-from a few ng/mL to >400 mg/mL (inorganic core mass). The high colloidal stability achieved with this long-chain zwitterionic ligand can be rationalized with the Alexander-De Gennes model that considers the increased particle-particle repulsion due to branched chains and ligand polydispersity. The versatility and immense practical utility of such colloids is showcased by the single NC spectroscopy on ultradilute samples and, conversely, by obtaining micrometer-thick, optically homogeneous dense NC films in a single spin-coating step from ultraconcentrated colloids.

Hollow ZSM-5 zeolites of size below one micrometer can be produced by desilication of crystals with aluminium zoning. The parent crystals have a core-shell structure: the core part has nearly no aluminium, whereas the aluminium content in the shell increases when extending to exterior surface. Transmission electron microscopy confirmed the preservation of the crystalline shell after base leaching, but could not identify its subtle change. An increase of the Si/Al ratio of the surface was detected upon leaching the parent material to form the hollow zeolite by using ambient pressure X-ray photoelectron spectroscopy and infrared spectroscopy of substituted alkylpyridines. 27 Al MAS NMR showed that base leaching results in a reduced percentage of distorted tetrahedrally coordinated aluminium. The reprecipitation of dissolved species occurs and tetrahedrally coordinated tin atoms can thus be introduced to the shell framework. Overall, the formation of hollow ZSM-5 zeolites by desilication involves not only the removal of silicon-rich core, but also a reduced percentage of exterior aluminium-related acid sites, which should be considered while using hollow zeolites in acid-catalyzed reactions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The conventional strategy of synthetic colloidal chemistry for bright and stable quantum dots has been the production of epitaxially matched core/shell heterostructures to mitigate the presence of deep trap states. This mindset has been shown to be incompatible with lead halide perovskite nanocrystals (LHP NCs) due to their dynamic surface and low melting point. Nevertheless, enhancements to their chemical stability are still in great demand for the deployment of LHP NCs in light-emitting devices. Rather than contend with their attributes, we propose a method in which we can utilize their dynamic, ionic lattice and uniquely defect-tolerant band structure to prepare non-epitaxial salt-shelled heterostructures that are able to stabilize these materials against their environment, while maintaining their excellent optical properties and increasing scattering to improve out-coupling efficiency. To do so, anchored LHP NCs are first synthesized through the heterogeneous nucleation of LHPs onto the surface of microcrystalline carriers, such as alkali halides. This first step stabilizes the LHP NCs against further merging, and this allows them to be coated with an additional inorganic shell through the surface-mediated reaction of amphiphilic Na and Br precursors in apolar media. These inorganically shelled NC@carrier composites offer significantly improved chemical stability toward polar organic solvents, such as γ-butyrolactone, acetonitrile, N -methylpyrrolidone, and trimethylamine, demonstrate high thermal stability with photoluminescence intensity reversibly dropping by no more than 40% at temperatures up to 120 °C, and improve compatibility with various UV-curable resins. This mindset for LHP NCs creates opportunities for their successful integration into next-generation light-emitting devices.

The potential implementation of ruthenium-based catalysts in polyvinyl chloride production via acetylene hydrochlorination is hindered by their inferior activity and stability compared to gold-based systems, despite their 4-fold lower price. Combining in-depth characterization and kinetic analysis we reveal the superior activity of ruthenium nanoparticles with an optimal size of 1.5 nm hosted on nitrogen-doped carbon (NC) and identify their deactivation modes: 1) nanoparticle redispersion into inactive single atoms and 2) coke formation at the metal sites. Tuning the density of the NC carrier enables a catalytic encapsulation of the ruthenium nanoparticles into single layer graphene shells at 1073 K that prevent the undesired metal redispersion. Finally, we show that feeding O 2 during acetylene hydrochlorination limits coke formation over the nanodesigned ruthenium catalyst, while the graphene layer is preserved, resulting in a stability increase of 20 times, thus rivalling the performance of gold-based systems., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Tin-based materials are an emerging class of Li-ion anodes with considerable potential for use in high-energy-density Li-ion batteries. However, the long-lasting electrochemical performance of Sn remains a formidable challenge due to the large volume changes occurring upon its lithiation. The prevailing approaches toward stabilization of such electrodes involve embedding Sn in the form of nanoparticles (NPs) in an active/inactive matrix. The matrix helps to buffer the volume changes of Sn, impart better electronic connectivity and prevent particle aggregation upon lithiation/delithiation. Herein, facile synthesis of Sn NPs embedded in a SiOC matrix via the pyrolysis of a preceramic polymer as a single-source precursor is reported. This polymer contains Sn 2-ethyl-hexanoate (Sn(Oct) 2 ) and poly(methylhydrosiloxane) as sources of Sn and Si, respectively. Upon functionalization with apolar divinyl benzene sidechains, the polymer is rendered compatible with Sn(Oct) 2 . This approach yields a homogeneous dispersion of Sn NPs in a SiOC matrix with sizes on the order of 5-30 nm. Anodes of the SiOC/Sn nanocomposite demonstrate high capacities of 644 and 553 mAh g -1 at current densities of 74.4 and 2232 mA g -1 (C/5 and 6C rates for graphite), respectively, and show superior rate capability with only 14% capacity decay at high currents., Competing Interests: The authors declare no conflict of interest., (© 2019 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)

Acid or base leaching are well-established tools in the synthesis of mesoporous zeolites. Previous studies suggest an inherent link between the structure-property relationship of mesoporous zeolites, that is, chemical resistance, pore diameter and distribution, with zeolite synthesis or crystallization conditions. The exact nature and/or origin of this link is currently however, poorly established. Here, we provide evidence how zeolite crystallization conditions influence the leaching behavior and thus structure of mesoporous zeolites. Electron microscopy and in situ small angle X-ray scattering both confirmed the crystallization of ZSM-5 to utilize both nanoparticles and oligomers as elemental building blocks. Utilization of these species is highly depended on supersaturation. The precursor solution of decreased water content favored a faster consumption of nanoparticles compared to its oligomers at the early stage of crystallization. Then the addition of oligomers can heal the surface imperfections and thus the resulting zeolite showed a higher resistance against acid leaching. In contrast, within the precursor solution of increased water content the slower consumption of nanoparticles led to crystals with a less robust rim. Defects existed in the rim due to limited healing by oligomers and, as such, mesopores can be created by the following post-treatment. Precise control over selected crystallization conditions can therefore further aid the design of optimized mesoporous zeolites., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Rechargeable magnesium batteries are appealing as safe, low-cost systems with high-energy-density storage that employ predominantly dendrite-free magnesium metal as the anode. While significant progress has been achieved with magnesium electrolytes in recent years, the further development of Mg-ion batteries, however, is inherently limited by the lack of suitable cathode materials, mainly due to the slow diffusion of high-charge-density Mg-ions in the intercalation-type host structures and kinetic limitations of conversion-type cathodes that often causes poor cyclic stability. Nanostructuring the cathode materials offers an effective means of mitigating these challenges, due to the reduced diffusion length and higher surface areas. In this context, we present the highly reversible insertion of Mg-ions into nanostructured conversion-type CuS cathode, delivering high capacities of 300 mAh g -1 at room temperature and high cyclic stability over 200 cycles at a current density of 0.1 A g -1 with a high coulombic efficiency of 99.9%. These materials clearly outperform bulk CuS, which is electrochemically active only at an elevated temperature of 50 °C. Our results not only point to the important role of nanomaterials in the enhancement of the kinetics of conversion reactions but also suggest that nanostructuring should be used as an integral tool in the exploration of new cathodes for multivalent, i.e., (Mg, Ca, Al)-ion batteries.

Hybrid organic-inorganic main-group metal halide compounds are the subject of intense research owing to their unique optoelectronic characteristics. In this work, we report the synthesis, structure, and electronic and optical properties of a family of hybrid tin (II) bromide compounds comprising guanidinium [G, C(NH 2 ) 3 + ] and mixed cesium-guanidinium cations: G 2 SnBr 4 , CsGSnBr 4 , and Cs 2 GSn 2 Br 7 . G 2 SnBr 4 has a one-dimensional structure that consists of chains of corner-sharing [SnBr 5 ] 2- square pyramids and G cations situated in between the chains. Cs + exhibits a pronounced structure-directing effect where a mixture of Cs + and G cations forms mono- and bilayered two-dimensional perovskites: CsGSnBr 4 and Cs 2 GSn 2 Br 7 . Furthermore, the flat shapes of the guanidinium cations induce anisotropic out-of-plane tilts of the [SnBr 6 ] 4- octahedra in the CsGSnBr 4 and Cs 2 GSn 2 Br 7 compounds. In G 2 SnBr 4 , the Sn lone pair is highly stereoactive and favors non-octahedral, that is, square pyramidal coordination of Sn(II). G 2 SnBr 4 exhibits bright broad-band emission from self-trapped excitonic states, owing to its soft lattice and electronic localization. This emission in G 2 SnBr 4 is characterized by a photoluminescence (PL) quantum yield of 2% at room temperature (RT; 75 ± 5% at 77 K) and a fast PL lifetime of 18 ns at room temperature., Competing Interests: The authors declare no competing financial interest.

Using heavy-atom labeling in conjunction with electron microscopy, we here visualize the distribution of point defects, i.e. internal silanol groups, in silicalite-1 zeolites at the single crystal level.