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Abstract Tailoring the atomic structural configuration at metal and oxide interface offers an effective route for the development of catalysts with optimized properties. Here, we report the design of a unique structural configuration of yolk-shell-like FePt-FeO x nanoparticles (NPs), that exhibits notably enhanced activity and stability towards CO oxidation at relatively low temperatures (<100 °C) compared with Pt NPs. The optimized FePt-FeO x catalysts were produced by partially reducing core-shell FePt-FeO x NPs under H 2 at 200 °C. The structural configuration was interrogated by advanced electron microscopy, which clearly reveals the evolution of the morphology, elemental segregation, and phase transition of FePt-FeO x NPs after the post-synthesis treatment. The generation of voids, partial crystallization of the FeO x shell and increased electron density on Pt were identified as key contributors to the enhanced activity and stability towards CO oxidation in FePt-FeO x NPs. This unique structural configuration allows for CO and O 2 diffusion through the FeO x shell with an increased exposure for CO and O 2 adsorption onto the core as well as an enhanced activation of O 2 compared with the core-shell FePt-FeO x without voids, which collectively boost the catalytic performance. Graphical abstract fx1 Highlights • Unique yolk-shell-like FePt-FeO x nanoparticles (NPs) were synthesized via simple post-synthesis treatments. • The structural configuration was elucidated at the atomic scale via advanced electron microscopy. • The yolk-shell-like FePt-FeO x NPs exhibit notably enhanced activity and stability towards CO oxidation at relatively low temperatures (<100 °C). [ABSTRACT FROM AUTHOR]

Selective breaking of the C-C bond in ethanol holds the key to many industrial processes, including the operation of direct ethanol fuel cells and steam reforming. Interstitial C atoms in the subsurface region of noble-metal catalysts have major impacts on the selectivity and activity, but an understanding of the mechanistic details is still elusive due to their nature of in situ formation and metastability. Herein, we develop a method to obtain stable RhC x (x ≈ 0.5) by introducing C atoms into the interstitial sites of well-defined Rh nanosheets of 8–10 at. layers in thickness, and further elucidate the electronic and geometric effects of the interstitial C atoms on the cleavage of C-C bond. With the introduction of C atoms into half of the octahedral sites, the Rh lattice changes from a cubic to an orthorhombic structure. The lattice expansion induced by the insertion of C atoms, together with the electron transfer between C and Rh atoms, effectively suppresses the coupling reaction between OH* and CH 3 CO* to form acetic acid while making the cleavage of C-C bond more exothermic. As such, we obtain a selectivity of ethanol to CO 2 as high as 18.1 %, much higher than those of the Rh counterpart (10.0 %), together with 3.1-fold improvement in kinetics. Guided by these findings, a new method is also developed to directly introduce C atoms into the subsurface of a commercial Rh black to enhance its selectivity and activity by 2.5- and 1.6- folds, respectively. [Display omitted] • Interstitial C atoms are introduced into the well-defined Rh nanosheets and the crystal structures are clearly resolved. • The electron transfer and the expanded lattice enhance both selectivity and activity for the cleavage of C-C bond in ethanol. • The insights are further utilized to directly modify the commercial Rh black to greatly improve its catalytic properties. [ABSTRACT FROM AUTHOR]

Hard-sphere-templating method has been widely used to synthesize hollow carbon spheres (HCSs), in which the spheres were firstly coated with a carbon precursor, followed by carbonization and core removal. The obtained HCSs are generally amorphous or weakly graphitized (with the help of graphitization catalysts). In this work, we report on the fabrication of graphitized HCSs and yolk–shell Au@HCS nanostructures using a modified templating method, in which smooth, uniform graphene layers were grown on SiO 2 spheres or Au@SiO 2 nanoparticles via metal-catalyst-free chemical vapor deposition (CVD) of methane. Our work not only provides a new method to fabricate high-quality, graphitized HCSs but also demonstrates a reliable approach to grow quality graphene on oxide surfaces using CVD without the presence of metal catalysts. [ABSTRACT FROM AUTHOR]

Development of renewable energy technologies requires advanced catalysts for efficient electrical-chemical energy conversion reactions. Here we report the study of Pt-Re alloy nanoparticles as an electrocatalyst for the oxygen reduction reaction (ORR). An organic solution approach is developed to synthesize monodisperse and homogeneous Pt 3 Re alloy nanoparticles. Electrochemical studies show that these nanoparticles exhibit an improvement factor of 4 in catalytic activity for the ORR compared to commercial Pt catalysts of similar particle sizes. Fundamental understanding of the structure-property relationship is established by combining material characterization using X-ray spectroscopy and atomically resolved electron microscopy, as well as Density Functional Theory (DFT) calculations. Our work revealed that an electronic modification of the surface properties of Pt by subsurface Re ( ligand effect ) accounts for the catalytic enhancement. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous carbon–Cr2O3 (M-C–Cr2O3) composite was prepared by co-assembly of in situ formed phenolic resin, chromium precursor, and Pluronic block copolymer under acidic conditions, followed by carbonization at 750°C under Argon. The TEM results confirmed that the Cr2O3 nanoparticles, ranging from 10 to 20nm, were well dispersed in the matrix of mesoporous carbon. The composite exhibited an initial reversible capacity of 710mAhg−1 and good cycling stability, which is mainly due to the synergic effects of carbons within the composites, i.e. confining the crystal growth of Cr2O3 during the high temperature treatment step and buffering the volume change of Cr2O3 during the cycling step. This composite material is a promising anode material for lithium ion batteries. [Copyright &y& Elsevier]

Abstract: In situ X-ray diffraction patterns were collected using a laboratory X-ray diffractometer during the first electrochemical charge/discharge cycle of the layered lithium excess compound Li[Li0.2Ni0.2Mn0.6]O2 in the family of Li[NixLi1/3−2x/3Mn2/3−x/3]O2 (x=1/5). Dynamic changes in peak positions, lattice parameters, and microstrain help to explain the lithium de-intercalation mechanism in this class of materials. Strong anisotropy is observed in the shifts of the lattice parameters during the first cycle. The in situ electrochemical measurement shows dynamically changing strain during the first electrochemical cycle that is explained by known lithium and transition metal (TM) migration mechanisms. [Copyright &y& Elsevier]

Abstract: Quantitative analysis of point defects is demonstrated through the use of multivariate statistical analysis. This analysis consists of principal component analysis for dimensional estimation and reduction, followed by independent component analysis to obtain physically meaningful, statistically independent factor images. Results from these analyses are presented in the form of factor images and scores. Factor images show characteristic intensity variations corresponding to physical structure changes, while scores relate how much those variations are present in the original data. The application of this technique is demonstrated on a set of experimental images of dislocation cores along a low-angle tilt grain boundary in strontium titanate. A relationship between chemical composition and lattice strain is highlighted in the analysis results, with picometer-scale shifts in several columns measurable from compositional changes in a separate column. [Copyright &y& Elsevier]

Abstract: Refractory Ti-bearing minerals in the calcium-, aluminum-rich inclusion (CAI) Inti, recovered from the comet 81P/Wild 2 sample, were examined using analytical (scanning) transmission electron microscopy (STEM) methods including imaging, nanodiffraction, energy-dispersive spectroscopy (EDX) and electron energy loss spectroscopy (EELS). Inti fassaite (Ca(Mg,Ti,Al)(Si,Al)2O6) was found to have a Ti3+/Ti4+ ratio of 2.0±0.2, consistent with fassaite in other solar system CAIs. The oxygen fugacity () of formation estimated from this ratio, assuming equilibration among phases at 1509K, is −19.4±1.3. This value is near the canonical solar nebula value (−18.1±0.3) and in close agreement with that reported for fassaite-bearing Allende CAIs (−19.8±0.9) by other researchers using the same assumptions. Nanocrystals of osbornite (Ti(V)N), 2–40nm in diameter, are embedded as inclusions within gehlenite, spinel and diopside in Inti. Vanadium is heterogeneously distributed within some osbornite crystals. Compositions range from pure TiN to Ti0.36V0.64N. The possible presence of oxide and carbide in solid solution with the osbornite was evaluated. The osbornite may contain O, but C is not present at detectable levels. The presence of osbornite, likely a refractory early condensate, together with the other refractory minerals in Inti, indicates that the parent comet contains solids that condensed closer to the proto-sun than the distance at which the parent comet itself accreted. The estimated oxygen fugacity and the reported isotopic and chemical compositions are consistent with Inti originating in the inner solar system like other meteoritic CAIs. These results provide insight for evaluating the validity of models of radial mass transport dynamics in the early solar system. The oxidation environments inferred for the Inti mineral assemblage are inconsistent with an X-wind formation scenario. In contrast, radial mixing models that allow accretion of components from different heliocentric distances can satisfy the observations from the cometary CAI Inti. [Copyright &y& Elsevier]

Abstract: This paper reports the anti-scuffing/anti-wear behavior and mechanism of an oil-miscible ionic liquid (IL), trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate, in a base oil at 1.0wt% concentration under both room and elevated temperatures. Results are benchmarked against those for a conventional anti-wear additive, zinc dialkyl-dithiophosphate (ZDDP). Reciprocating sliding, boundary lubrication tests were conducted using a piston ring segment against a cylinder liner piece cut from actual automotive engine components. Although the IL and ZDDP worked equally well to prevent scuffing and reduce wear in the room-temperature tests, the IL significantly outperformed ZDDP in the 100°C tests. The top surfaces and cross sections of the worn surfaces were characterized to reveal the morphology, thickness, nanostructure, and chemical composition of the IL-induced tribo-films. [Copyright &y& Elsevier]

Abstract: Herein, we report novel gold catalysts made by dispersing Au@Fe2O3 core–shell structures on solid supports. In the synthesis of Au@Fe2O3 core–shell structures, dodecanethiol-capped gold nanoparticles were used as the seed and Fe(CO)5 was used as the precursor to Fe2O3 shell. The Au@Fe2O3 core–shell particles were deposited onto SiO2 support to obtain Au@Fe2O3/SiO2 catalysts that were highly active for low-temperature CO oxidation. The catalytic activity was even higher than that of Au/SiO2 or Au/Fe2O3 prepared by colloidal deposition with comparable gold loadings. The influences of thermal pretreatment, shell thickness, and different supports (e.g., SiO2, TiO2, C, Fe2O3) were investigated, and relevant characterization using TG/DTG, XRD, TEM, HAADF, and EDX was conducted. [ABSTRACT FROM AUTHOR]

The efficient transformation of CO 2 into a value-added material is a potential strategy to help mitigate climate effects caused by CO 2 emissions. One potential CO 2 conversion product is graphite which is an important and versatile material extensively used in many applications including as an anode for lithium-ion batteries (LIBs). Commercial graphite, however, is traditionally synthesized via the energy intensive Acheson process (>3000 °C) and the performance of such graphite can be limited under fast charging conditions which is important for vehicle electrification. Herein, we report the electrochemical transformation of CO 2 to highly crystalline nano-graphite with a controlled microstructure in a carbonate molten salt at 780 °C. The use of a nickel foam electrode and controlled electrochemical parameters during the molten salt conversion process yielded pure graphite at a lower temperature compared to the Acheson process. Moreover, when investigated as an anode material for LIBs, the CO 2 -converted graphite exhibited high reversible capacity, long cycle life, and excellent rate capability even under fast charging conditions. This process provides a way to potentially reduce carbon emissions through the utilization of waste CO 2 by converting it into value-added graphite suitable for fast charging, high-energy-density batteries for vehicle electrification. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3 Cu 0.25 Co 0.75 (NdCuCo) and Pr 3 Cu 0.25 Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract: Self-organized amorphous TiO2 nanotube arrays (NTAs) were successfully fabricated on both Ti foil and porous Ti foam through electrochemical anodization techniques. The starting Ti foams were fabricated using ARCAM''s Electron Beam Melting (EBM) technology. The TiO2 NTAs on Ti foam were used as anodes in lithium ion batteries; they exhibited high capacities of 103 μAh cm−2 at 10 μA cm−2 and 83 μAh cm−2 at 500 μA cm−2, which are two to three times higher than those achieved on the standard Ti foil, which is around 40 μAh cm−2 at 10 μA cm−2 and 24 μAh cm−2 at 500 μA cm−2, respectively. This improvement is mainly attributed to higher surface area of the Ti foam and higher porosity of the nanotube arrays layer grown on the Ti foam. In addition, a Na-ion half-cell composed of these NTAs anodes and Na metal as the counter electrode showed a self-improved specific capacity upon cycling at 10 μA cm−2. These results indicate that TiO2 NTAs grown on Ti porous foam are promising electrodes for Li-ion or Na-ion rechargeable batteries. [Copyright &y& Elsevier]

Abstract: For high-voltage cycling of rechargeable Li batteries, a nano-scale amorphous Li-ion conductor, lithium phosphorus oxynitride (Lipon), has been coated on surfaces of LiCoO2 particles by combining a RF-magnetron sputtering technique and mechanical agitation of LiCoO2 powders. LiCoO2 particles coated with 0.36wt% (∼1nm thick) of the amorphous Lipon, retain 90% of their original capacity compared to non-coated cathode materials that retain only 65% of their original capacity after more than 40 cycles in the 3.0–4.4V range with a standard carbonate electrolyte. The reason for the better high-voltage cycling behavior is attributed to reduction in the side reactions that cause increase of the cell resistance during cycling. Further, Lipon coated particles are not damaged, whereas uncoated particles are badly cracked after cycling. Extending the charge of Lipon-coated LiCoO2 to higher voltage enhances the specific capacity, but more importantly the Lipon-coated material is also more stable and tolerant of high voltage excursions. A drawback of Lipon coating, particularly as thicker films are applied to cathode powders, is the increased electronic resistance that reduces the power performance. [Copyright &y& Elsevier]

Abstract: Silica is one of the most widely used catalyst supports for metal nanocatalysts. Although the sintering of metal nanoparticles on various silica supports has been extensively studied, the restructuring of silica supports and its effect on supported metal nanoparticles have been seldom investigated. In this paper, silica-supported gold catalysts were used as a model system to probe the interplay of silica supports and metal nanoparticles under high-temperature treatment conditions. Gold was loaded onto mesoporous SiO2 (SBA-15) using Au(en)2Cl3 as the precursor in the presence of aqueous NaOH (pH∼10). The influence of high-temperature treatment on the textural and structural changes of SBA-15 and Au/SBA-15 was studied by X-ray diffraction (XRD), N2 adsorption–desorption, and transmission electron microscopy (TEM). Control experiments were conducted using an amorphous SiO2 (Cab-O-Sil) as the support. It was found that SBA-15 undergoes significant phase transformation to crystalline cristobalite upon high-temperature treatment, resulting in the dramatic decrease in surface area. More interestingly, the crystallization of SiO2 leads to the encapsulation of gold nanoparticles inside the SiO2 matrix. This conclusion was proven by aqua regia leaching, EDX, and SEM/TEM experiments. Gold nanoparticles can also be encapsulated into the SiO2 matrix when using Cab-O-Sil as the support, but the process takes place under much higher temperatures. The encapsulation of gold nanoparticles can be mitigated by coating Au/SBA-15 with amorphous Al2O3 or by coating SBA-15 with Al2O3 before loading gold. Our findings shed new light on the deactivation of supported gold catalysts under high-temperature conditions. [ABSTRACT FROM AUTHOR]