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Pit corrosion of Li during stripping is an important factor responsible for poor Li cycling efficiency, a metric that determines its cycling life. When excess Li is present, it has been observed that Li tends to strip in a non-uniform fashion, forming pits that extend well past the theoretical Li depth that inevitably lead to the formation of electronically isolated “dead” Li particles. In this work, a novel cell with replenishable Li is shown to inherently mitigate the formation of this “dead” Li, as a direct result of a design in which the intrinsically more homogenous stripping behavior of anode-free cells are combined with a replenishable limited Li reservoir. These novel cells (Li|Cu||LiFePO4) exhibit 25% and 34% higher cumulative capacities than the conventional cells (Cu|Li||LiFePO4) in carbonate and ether electrolytes, respectively, enabling a significant increase in cycle life without impacting energy density. This improvement strategy represents a new direction in Li metal battery improvement, in which improved cycling can be achieved regardless of electrolyte chemistry.

Supported ruthenium based materials are active for the catalytic hydrogenation of biomass-derived molecules. However, such catalysts still have problems regarding deactivation coming from Ru leaching and particles aggregation. In this work we demonstrate that spatial restriction on metal nanoparticles limits aggregation and eliminates performance losses upon subsequent testing. We synthesized and compared Ru supported on activated (Ru/AC) or mesoporous carbon (Ru/MC). Electron tomography characterization showed preferential Ru location depending on the material porosity; Ru nanoparticles were located inside mesoporous carbon pores and showed narrower size distribution. In catalytic reactions, Ru/MC reached the complete conversion of levulinic acid with the 96% selectivity to γ-valerolactone while it converted 74% of glycerol compared to the 34% showed by Ru/AC. The Ru/AC materials deactivated after 1 catalytic cycle, however the Ru/MC maintained constant activity for multiple catalytic cycles.

In this work we report a framework to understand the role of solvent-salt interactions and how they mediate the performance of sodium-air/O2 batteries. The utilization of suitable electrolyte materials remains a point of major concern within the research community, as their stability and decomposition pathways during cycling are intimately connected with capacity and cycle life. Glyme based solvents have been widely utilized in Na–O2 batteries, however, to date no clear correlation between solvent/electrolyte properties and battery performance has been given. Herein, we have examined the effect of glyme chain length (ethylene glycol dimethyl ether DME; diethylene glycol dimethyl ether, DEGDME; and tetraethylene glycol dimethyl ether, TEGME) on the cycling behaviour of Na–O2 batteries and conclude that overall cell performance is highly dependent on solvent selection, salt concentration and rate of discharge/charge. We demonstrate how solvent selection helps define cell chemistry and performance by linking salt-solvent interactions to enthalpy of dissolution - and subsequently to sodium battery electrolyte properties - through the combination of both experimental and theoretical methodologies. The approaches detailed in this study could be used to predictively prepare electrolytes for Li-air batteries, other glyme-based electrochemical systems and low temperature applications.

Summary We employ tip-enhanced Raman spectroscopy (TERS) to study model amorphous silicon (a-Si) thin film anodes galvanostatically cycled for different numbers. For the 1× cycled a-Si, TERS shows good correlation between solid electrolyte interphase (SEI) topography and chemical mapping, corresponding to distribution of lithium ethylene dicarbonate (LEDC) and poly (ethylene oxide) (PEO)-like oligomer species. Subsequent electrochemical cycling makes the SEI relatively thick and rough with the chemical composition heavily dominated by LEDC monomer-dimer for 5× cycled a-Si. For 20× cycled a-Si, the TERS signal is dominated by carboxylate (RCO2Li) compounds of various conformations and fluorinated species (LixPOyFz). A nanomosaic-multilayer hybrid SEI model on top of the a-Si anode is proposed. The significance of this work is applicable not only to silicon, where SEI plays a dominant role in determining the cycle life performance and reversibility, but also for a number of other relevant battery chemistries such as Na-ion and multivalent redox systems.

Thermal insulation materials are crucial to improve the energy performance of buildings and industrial applications. We report an approach to create hermetically vacuum-sealed silica-based hollow microspheres that can lower the thermal conductivity of closed-cell insulation materials. The wall structure of these hollow microspheres includes a reticulated network of pores or channels that extend through the thickness of the wall. When a thin layer of glass material is applied to the wall exterior, followed by a vacuum-assisted thermal treatment process, the coated microsphere surfaces display a highly dense conformal coverage and near-complete elimination of surface porosity. The sealing efficiency of these microspheres is verified by trapping argon within their cavities as well as through evacuating their hollow cores. Notably, incorporating the evacuated microspheres into a polymer matrix resulted in ∼27% enhancement in its thermal insulation performance and no notable loss of performance was observed following three months of exposure to ambient conditions. Thus, we believe that the present study offers a commercially viable strategy that opens the door to applications of such inorganic hollow particles in areas ranging from vacuum-based thermal insulation systems to catalysis, separation technologies, and medical fields.

This study explores low molecular weight polymers with the same chemical repeat structure as high molecular weight poly acrylic acid (PAA) and lithium poly acrylic acid (LiPAA) binders which act as a dispersant to improve the silicon-graphite electrode performance. The electrodes which utilize LiPAA as a dispersant perform, on average, the best with respect to the maximum capacity (compared to theoretical), rate performance, and capacity retention with time. These electrodes also have the poorest dispersion of binder, indicating that the poor binder dispersion is essential to electrode performance. In contrast, this study shows that electrodes formulated using PAA had good dispersion and performs the worst in cycling. Finally, this work demonstrates that the binder is not uniformly distributed in the electrode, but rather resides in local regions. The results indicate these regions accommodate volume expansion during cycling.

Scaffold structures of electrospun aluminum–substituted lithium lanthanum zirconate Li7La3Zr2O12 (Al-LLZO) were synthesized and used as an additive in a LiNi0.6Mn0.2Co0.2O2 composite cathode. The scaffolds were crystalized in the cubic phase after calcination at 700 °C. The Al-LLZO scaffold morphology was dependent on the precursor formulation (aqueous and dimethylformamide. The aqueous precursors resulted in scaffolds of densely coalesced ligaments, whereas the dimethylformamide precursors resulted in high–aspect ratio nanofiber scaffolds. The long-term cycling stability and rate performance of the cells were found to depend on the Al-LLZO scaffold morphology. The uniformly dispersed Al-LLZO fibers resulted in a more stable cathode electrolyte interface formation through the reduced decomposition of the LiPF6 salt during cycling, resulting in a better high-rate and long-term cycling performance.

Recent advancements in Li and Li-ion based energy storage resulted in development of novel electrode materials for higher energy density which are finding their applications in transportation. There appears to be a limitation in improvement of specific energy of the system based solely on design of material compositions for multivalent intercalation compounds. In addition, higher energy stored by the system implies need for addressing safety concerns especially when it comes to large automotive battery packs. New approaches for improvement of both energy density and safety of batteries are emerging, where multifunctionality of the materials and/or architectures is utilized. This article presents a review for such approaches from multifunctional current collectors to design of batteries capable of supporting mechanical loads and thus possessing ability to be used as a structural component.

The high surface area and electrical conductivity of few-layered graphene would make it an ideal catalyst support and electrode in fuel cells apart from its susceptibility to oxidative corrosion. Here we report the single-step, bottom-up synthesis of oxidation-resistant boron-doped graphene and show its increased stability in the aggressive electrochemical environment of intermediate temperature solid acid fuel cells (SAFCs). Boron was shown to alter the growth mode of single walled carbon nanohorns by laser vaporization to produce high yields of thin ( 140 °C, with large fractions of multilayered B-GLFs surviving 10 °C/min ramps to 1000 °C. These B-GLFs provided a stable Pt catalyst support and electrode over 40 h operation in SAFCs with cesium dihydrogen phosphate electrolyte operating at 250 °C, as opposed to undoped GLFs or SWCNHs which were nearly completely consumed. The facile synthesis and oxidation-resistant properties of boron-doped GLF appear promising for graphene applications in oxidizing environments.

A series of lithium difluoro-2-fluoro-2-alkyl-malonatoborate salts have been used as additives in conventional 1.0 M LiPF6/ethylene carbonate (EC)-dimethyl carbonate (DMC)-diethyl carbonate (DEC) (1-1-1, by v) electrolyte for high voltage LiNi0.5Mn1.5O4 (LNMO) based lithium metal and lithium ion batteries. Cyclic voltammograms (CVs) reveal that the electrolytes with additives can significantly suppress the co-intercalation of solvents into the graphene layers during the first cycle due to their sacrificial reductions on the surface of the graphite electrode above 1.0 V vs Li/Li+. In addition, CVs reveal that the electrolyte without additive suffers from extensive electrolyte oxidation on the surface of the LNMO electrode during the first cycle, resulting in the biggest increase of the total cell impedance. Furthermore, electrochemical floating test shows less oxidation current in the electrolytes with additives at voltages above 5.0 V, proving good passivation by the additives. More importantly, the presence of additives can effectively increase the first cycle coulombic efficiencies and cycling stability in the LNMO based lithium metal and lithium ion batteries. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) show that with additives compact solid electrolyte interphase (SEI) and thinner passivation layer are formed on the surfaces of the graphite and LNMO electrode, respectively. Finally, these salt additives can better protect the current collector from corrosion, further confirming their effectiveness in conventional electrolytes for high-voltage lithium metal and lithium ion batteries.

Single crystals of ( Nd 1 − x Ce x ) 2 Fe 14 B , some reaching ∼ 6 × 8 × 8 mm 3 in volume, are grown out of Fe-(Nd, Ce) flux. This crystal growth method allows for large ( Nd 1 − x Ce x ) 2 Fe 14 B single crystals to be synthesized using a simple flux growth procedure. Chemical and structural analyses of the crystals indicate that ( Nd 1 − x Ce x ) 2 Fe 14 B forms a solid solution until at least x =0.38 with a Vegard-like variation of the lattice constants with x . Refinements of single crystal neutron diffraction data indicate that Ce has a slight site preference (7:3) for the 4 g rare earth site over the 4 f site. Magnetization measurements at 300 K show only small decreases with increasing Ce content in saturation magnetization ( M s ) and anisotropy field ( H A ), and Curie temperature ( T C ). First principles calculations are carried out to understand the effect of Ce substitution on the electronic and magnetic properties. For a multitude of applications, it is expected that the advantage of incorporating lower-cost and more abundant Ce will outweigh the small adverse effects on magnetic properties. Ce-substituted Nd 2 Fe 14 B is therefore a potential high-performance permanent magnet material with substantially reduced Nd content.

This work presents a soft templating approach for mesoporous carbon using the polyphenolic heterogeneous biomass, chestnut tannin, as the carbon precursor. By varying synthesis parameters such as tannin:surfactant ratio, cross-linker, reaction time and acid catalyst, the pore structure could be controllably modulated from lamellar to a more ordered hexagonal array. Carbonization at 600 °C under nitrogen produced a bimodal micro-mesoporous carbonaceous material exhibiting enhanced hydrogen bonding with the soft template, similar to that shown by soft-templating of phenolic-formaldehyde resins, allowing for a tailorable pore size. By utilizing the acidic nature of chestnut tannin (i.e. gallic and ellagic acid), hexagonal-type mesostructures were formed without the use of an acid catalyst. The porous carbon materials were activated with ammonia to increase the available surface area and incorporate nitrogen-containing functionality which led to a maximum CO2 adsorption capacity at 1 bar of 3.44 mmol/g and 2.27 mmol/g at 0 °C and 25 °C, respectively. The ammonia-activated carbon exhibited multiple peaks in the adsorption energy distribution which indicates heterogeneity of adsorption sites for CO2 capture.

Capacity loss was observed in Li-ion cells after mechanical deformation approaching the onset of internal short circuit (ISCr). In this paper, a series of indentation tests were carried out on commercial Li-ion cells of three capacities (500, 1500 and 2000 mAh). Both in-situ and ex-situ methods were used to investigate the mechanisms of indentation-induced capacity loss. After indentation test, the cell capacity reduced by 0.5%–6% of its original value. The incremental capacity (IC) analysis results showed that IC curves generally shifted to lower voltage region, indicating the increase in cell internal resistance. In addition, the fitting results of electrochemical impedance spectroscopy (EIS) indicated that mechanical indentation can result in a reduction in ohmic resistance and the increase in polarization resistance. Scanning electron microscopy (SEM) and X-ray computed tomography (XCT) results showed crushing of graphite, mud cracking of copper current collectors and enlarged pores in separator, which is proposed to be the main reasons for the increase in polarization resistance and permanent capacity loss. The rapid capacity loss due to mechanical abuse was compared with the long-term capacity fading.

Two physical vapor deposition (PVD) processes, magnetron sputtering (MS) and arc plasma deposition (APD), were investigated to prepare oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). The catalysts are composed of Pt or Pt alloy on a NbOx decorated carbon support (NbOx/C). The combination of these materials results in tunable structures and electronic properties and a commensurate increase in lifetime (>60% retention after 30,000 cycles) and initial MEA mass activities of over 300 AgPt−1. In situ x-ray absorption spectroscopy (XAS) shows that there exists direct interaction between Pt and the O in the non-stoichiometric NbOx in Pt on NbOx/C catalyst. The introduction of Co leads to shortened Pt–Pt bond distance as confirmed by XAS, and a beneficial Pt on NbOx strain effect. The relationship between Pt and NbOx loading is discussed based on rotating disk electrode (RDE) data.

Several high-purity methyl perfluorocarboxylates were prepared (>99.5% purity by mole) and investigated as potential fluorine-rich electrolyte solvents in Li-ion batteries. The most conductive electrolyte, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethyl perfluoroglutarate (PF5M2) (ionic conductivity = 1.87 × 10−2 mS cm−1), is investigated in Si thin-film half-cells. The solid-electrolyte-interphase (SEI) formed by the PF5M2 electrolyte is composed of similar organic and inorganic moieties and at comparable concentrations as those formed by ethylene carbonate/dimethyl carbonate electrolytes containing LiPF6 and LiTFSI salts. However, the SEI formed by the PF5M2 electrolyte undergoes reversible electrochemical defluorination, contributing to the reversible capacity of the cell and compensating in part for capacity fade in the Si electrode. While far from ideal these electrolytes provide an opportunity to further develop predictions of suitable fluorinated molecules for use in battery solvents.

The roundtrip electrochemical energy efficiency is improved from 63% to 76% at a current density of 200 mA cm−2 in an all-vanadium redox flow battery (VRFB) by utilizing modified carbon paper electrodes in the high-performance no-gap design. Heat treatment of the carbon paper electrodes in a 42% oxygen/58% nitrogen atmosphere increases the electrochemically wetted surface area from 0.24 to 51.22 m2 g−1, resulting in a 100–140 mV decrease in activation overpotential at operationally relevant current densities. An enriched oxygen environment decreases the amount of treatment time required to achieve high surface area. The increased efficiency and greater depth of discharge doubles the total usable energy stored in a fixed amount of electrolyte during operation at 200 mA cm−2.

In this work we have determined the room temperature electrochemical reactions of SnO2 thin films and mesoporous carbons filled with SnO2 anodes with Na, and compare the results with those obtained during the reaction with Li. We show that SnO2 can reversibly deliver up to 6.2 Li/SnO2 whereas the reaction with Na is significantly limited. The initial discharge capacity is equivalent to less than 4 Na/SnO2, which is expected to correspond to the formation of 2 Na2O and Sn. This limited discharge capacity suggests the negative role of the formed Na2O matrix upon the reversible reaction of Sn clusters. Moreover, the reversible cycling of less than 1 Na/SnO2, despite the utilization of 6–7 nm SnO2 particles, is indicative of sluggish reaction kinetics. The origin of this significant capacity reduction is probably due to the formation of a diffusion limiting interface. Furthermore, there is a larger apparent hysteresis compared to Li. These results point to the need to design composite structures of SnO2 nanoparticles with suitable morphological and conductivity components.

In this study, alkali doped fullerenes synthesized by two different solvent assisted mixing techniques are compared for their hydrogen uptake activity. In particular, we investigated the interaction of hydrogen with lithium and sodium doped fullerenes via physisorption. In addition, we present the first mass spectrometric evidence for the formation of C 60 H 60 via chemisorption. Hydrogen physisorption isotherms up to 1 atm at temperatures ranging from 77 K to 303 K were measured demonstrating an increase in hydrogen uptake versus pure C 60 and increased isosteric heats of adsorption for the lithium doped fullerene Li 12 C 60 . The hydrogen uptake in Na 6 C 60 , Li 6 C 60 , and Li 12 C 60 was enhanced compared to pure C 60 . However, despite these improvements the low amount of physisorbed hydrogen at 1 atm and 77 K in these materials suggests that fullerenes do not possess enough accessible surface area to effectively store hydrogen due to their close packed crystalline nature.

Indium thin films were evaluated as an anode material for Li-ion and Na-ion batteries (theoretical capacities of 1012 mAh g −1 for Li and 467 mAh g −1 for Na). XRD data reveal that several known Li–In phases (LiIn, Li 3 In 2 , LiIn 2 and Li 13 In 3 ) form providing 950 mAh g −1 reversible capacity. In contrast, the reaction with Na is severely limited (75–125 mAh g −1 ). XRD data of short-circuited cells (40 h at 65 °C) show the coexistence of NaIn, In, and an unknown Na x In phase. In electrodes exhibit anomalous electrolyte decomposition characterized by large discharge plateaus at 1.4 V vs Li/Li + and 0.9 V vs Na/Na + . The presence of 5 wt% fluoroethylene carbonate additive suppresses the occurrence of the electrolyte decomposition during the first cycle but does not necessarily prevent it upon further cycling. Prevention of the anomalous decomposition can be achieved by restricting the (dis)charge voltages, increasing the current or by using larger amounts of FEC. The native surface oxides (In 2 O 3 ) are responsible for the pronounced electrolyte decomposition during the first cycle while other In 3+ species are responsible during the subsequent cycles. We also show that indium electrodes can exhibit very high rate capability for both Li (100 C-rate) and Na (30 C-rate).

This work demonstrates a quantitative method to determine the hydrogen evolution rate occurring at the negative carbon electrode of the all vanadium redox flow battery (VRFB). Two carbon papers examined by buoyancy measurements yield distinct hydrogen formation rates (0.170 and 0.005 μmol min−1 g−1). The carbon papers have been characterized using electron microscopy, nitrogen gas adsorption, capacitance measurement by electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). We find that the specific electrochemical surface area (ECSA) of the carbon material has a strong influence on the hydrogen generation rate. This is discussed in light of the use of high surface area material to obtain high reaction rates in the VRFB.

Metal oxides are commonly used as the supports of gold nanoparticles for catalytic CO oxidation, whereas metal salts are rarely considered suitable supports. In the present work, we developed a new kind of gold nanocatalyst supported on heterostructured PbSO4-MCF mesoporous materials that was prepared by an in situ growth method using dodecylbenzenesulfonate (SOBS) as a sulfonate precursor. It was found that an Au/PbSO4-MCF (SDBS) catalyst preheated at 300 degrees C showed high CO conversion below 100 degrees C. In addition, the stability of selected catalysts was studied as a function of time on stream. Because of the alteration of surface properties, these Au nanocatalysts were highly sinter-resistant. Published by Elsevier B.V.

The electrochemical reactions of amorphous/nanocrystalline AlSb thin films prepared by magnetron sputtering are reported for the first time. The reaction with Li proceeds with an average reaction potential of 0.65 V, a reversible capacity of 750 mAh g−1, and very fast reaction kinetics. A storage capacity close to 500 mAh g−1 (70% of the maximum capacity) is achieved at 125 C-rate. Only small increases in overpotentials are measured with increasing currents: ∼0.15 V at 12 C and ∼0.7 V at 125 C. In contrast, the reaction with Na results in average reaction potential of 0.5 V and a storage capacity of 450 mAh g−1. The capacity retention and reaction kinetics with Na are presently not satisfactory with pronounced capacity losses upon cycling and larger overpotentials with increasing current. The capacity retention can be improved by using FEC additive in the Na-ion electrolyte, which highlights that the SEI plays an important role for the electrode cycling stability. The study of the reaction mechanism by X-ray diffraction reveals that the electrode material remains amorphous at all potentials, and suggests that during the reaction with Li the atomic short range ordering is similar to the expected phases.

This work reports a method to explore the catalytic reactivity of electrode surfaces toward the decomposition of carbonate solvents [ethylene carbonate (EC), dimethyl carbonate (DMC), and EC/DMC]. We show that the decomposition of a 1:1 wt% EC/DMC mixture is accelerated over certain commercially available LiCoO 2 materials resulting in the formation of CO 2 while over pure EC or DMC the reaction is much slower or negligible. The solubility of the produced CO 2 in carbonate solvents is high (0.025 g mL −1 ) which masks the effect of electrolyte decomposition during storage or use. The origin of this decomposition is not clear but it is expected to be present on other cathode materials and may affect the analysis of SEI products as well as the safety of Li-ion batteries.

Phosphorylated mesoporous carbons (PMCs) were investigated as catalysts in the dehydration of fructose to hydroxymethylfurfural (HMF). The acidic PMCs show better selectivity to HMF compared to sulfonated carbon catalyst (SC) despite lower activity. The concentration of P–O groups on the PMC was correlated with the activity/selectivity of the catalysts; the higher the P–O concentration, the higher the activity. However, the higher the P–O content, the lower the selectivity to HMF. Indeed, a lower concentration of the P–O groups minimized the degradation of HMF to levulinic acid and the formation of by-products, such as humines. Stability tests showed that these systems deactivate due to the formation of humines and water insoluble by-products derived from the dehydration of fructose which blocked the catalytically active sites.

The effect of coating the high voltage spinel cathode LiMn 1.5 Ni 0.5 O 4 with three metal oxide thin layers is discussed. Instead of the typical powder electrodes with poorly defined surface coatings, thin film electrodes were prepared with well-defined oxide coating thicknesses to investigate the influence of coating on surface reactivity via X-ray photoelectron spectroscopy (XPS). ZnO is found to decompose during the first charge whereas Al 2 O 3 and ZrO 2 are stable for more than 100 cycles. ZrO 2 , however, importantly limits the available Li storage capacity of the electrochemical reaction due to poorer kinetics. Al 2 O 3 offers the best results in term of capacity retention. Upon cycling, the evidence of a signal at 75.4 eV in the Al2p binding energy spectrum indicates the partial fluorination of Al 2 O 3 into, perhaps, Al 2 O 2 F 2 . Moreover, the continuous formation of ethers, esters and Li x PO y F z compounds on the surface of the electrodes is found for all coating materials.

Cu2Sb thin films prepared by magnetron sputtering are evaluated as an anode material for Na-ion batteries. The starting material is composed of nanocrystallites with the desired tetragonal P4/nmm structure. The study of the reaction mechanism reveals the formation of an amorphous/nanocrystalline phase of composition close to Na3Sb as the final reaction product. The solid electrolyte interphase (SEI) material is mostly composed of carbonates (Na2CO3, NaCO3R) and possibly ethers. The Cu2Sb anode possesses moderate capacity retention with a reversible storage capacity (250 mAh/g or 2100 mAh/cm3) close to the theoretical value (323 mAh/g), an average reaction potential of around 0.55 V vs. Na/Na+, and a high rate performance (10 C-rate). Keywords: Copper antimony (Cu2Sb) anodes, Thin film electrodes, Na3Sb composition, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS)

This article reports the evidence of surface film formation because of the breakdown of electrolyte upon high voltage cycling (4.9 V) of lithium rich cathode having a nominal composition of, Li1.2Mn0.525Ni0.175Co0.1O2. We studied the chemical composition of this passivation film using electrochemical impedance, X-ray Photoelectron and micro-Raman spectroscopy and the results were compared against the pristine electrode. In order to distinguish the changes in the surface films composition induced by prolonged electrochemical cycling versus chemical passivation effect, we also studied the surface composition of cathode powders aged with electrolytes at 60 oC. Our study shows that electrodes cycled beyond 150 cycles showed a rapid drop in capacity due to increase in the surface film resistance resulting in limited capacity utilization.

Li-rich and stoichiometric Li 1 Mn 1.5 Ni 0.5 O 4 (LMNO) cathode films have been successfully prepared by magnetron sputtering. Sputtering from a Li stoichiometric target yields Li-rich films composed of spinel, layered and monoclinic phases. Films obtained from a Li deficient target are mostly made of a spinel phase and little layered material. The resulting cathode thin films have good capacity retention and very high rate capability. The reaction mechanism has been investigated by XRD and HRTEM and evidences the reversible formation of a spinel phase, as is generally found for the powder samples. The film geometry enables us to understand the effect of coatings (ZnO or LiPON). Coating high voltage cathodes reduces the coulombic losses, but at the price of rate performance. Nonetheless, these coated sputtered electrode thin films offer a higher rate capability than other LMNO thin films obtained by other physical vapor deposition techniques.

Bi has been widely employed as a modifier for Pd and Pt based catalyst mainly in order to improve selectivity. We found that when Bi was added to the bimetallic system AuPd, the effect on activity in alcohol oxidation mainly depends on the amount of Bi regardless its position, being negligible when Bi was 0.1 wt% and detectably negative when the amount was increased to 3 wt%. However, the selectivity of the reactions notably varied only when Bi was deposited on the surface of metal nanoparticles suppressing parallel reaction in both benzyl alcohol and glycerol oxidation. After a careful characterization of all the catalysts and additional catalytic tests, we concluded that the Bi influence on the activity of the catalysts could be ascribed to electronic effect whereas the one on selectivity mainly to a geometric modification. Moreover, the Bi-modified AuPd/AC catalyst showed possible application in the production of tartronic acid, a useful intermediate, from glycerol.

Soft-templated phosphorylated mesoporous carbons with homogeneous distributions of phosphate groups were prepared by a 'one-pot' synthesis method using mixtures of phosphoric acid with hydrochloric, or nitric acids in the presence of Pluronic F127 triblock copolymer. Adjusting the various ratios of phosphoric acid used in these mixtures resulted in carbons with distinct adsorption, structural and surface acidity properties. The pore size distributions (PSDs) from nitrogen adsorption at -196 C showed that mesoporous carbons exhibit specific surface areas as high as 551 m{sup 2}/g and mesopores as large as 13 nm. Both structural ordering of the mesopores and the final phosphate contents were strongly dependent on the ratios of H{sub 3}PO{sub 4} in the synthesis gels, as shown by transmission electron microscopy (TEM), X-ray photoelectron (XPS) and energy dispersive X-ray spectroscopy (EDS). The number of surface acid sites determined from temperature programmed desorption of ammonia (NH{sub 3}-TPD) were in the range of 0.3-1.5 mmol/g while the active surface areas are estimated to comprise 5-54% of the total surface areas. Finally, the conversion temperatures for the isopropanol dehydration were lowered by as much as 100 C by transitioning from the least acidic to the most acidic catalysts surface.

We report electrochemical studies of high voltage cathodes composed of lithium rich “layered-layered” material having the nominal composition Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 , or equivalently 0.6Li[Li 1/3 Mn 2/3 ]O 2 –0.4Li[Mn 0.3 Ni 0.45 Co 0.25 ]O 2 . These aspects were investigated by cyclic voltammetry studies in conjunction with electrochemical impedance spectroscopy measurements to understand the redox reactions involving multiple transition metals and their capacity contribution at higher voltages, up to 4.9 V. Further, cathodes with 1.5 wt.% carbon nanofibers added to the Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 composite electrode showed stable reversible capacities of about 280 mAh g −1 when cycled to 4.9 V for more than 100 cycles, and almost a factor of two improvements in the rate performance compared to the electrode composition prepared using conventional composition (7.5% carbon black and 7.5% binder).

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 0.36 wt% (∼1 nm 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 3.0–4.4 V 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.

Here, we investigated the properties of Au nanoparticles prepared via three different techniques and supported on three different MgAl 2 O 4 spinels. After careful characterization of bare and gold-loaded supports (XPS, BET, XRD, STEM) and catalytic test for the selective oxidation of glycerol, we concluded that the surface composition and area of the spinel play an important role in determining the selectivity of the catalyst as well as gold particle size. When supported on surface characterized by a similar Al/Mg ratio, gold clusters selectivity is not mediated by particle dimension. For example, large gold particles on MgAl 2 O 4 , which typically produce high selectivity to glycerate when supported on aluminum-rich surfaces instead, enhance the C–C bond cleavage reaction. Accordingly, the selectivity of similarly sized AuNPs on MgAl 2 O 4 spinels with the same surface Al/Mg ratio is similar but we demonstrate that the activity depends on gold surface exposure (at.% Au by XPS) and on support surface area.

2.5 nm gold nanoparticles were grown on a fumed silica support, using the physical vapor deposition technique of magnetron sputtering, that are thermally stable when annealed in an oxygen containing environment up to at least 500 °C. Traditional Au/TiO 2 catalysts rapidly sinter to form large 13.9 nm gold clusters under these annealing conditions. This surprising stability of Au/SiO 2 is attributed to the absence of residual impurities (ensured by the halide-free production method) and a strong bond between gold and defects at the silica surface (about 3 eV per bond) estimated from density functional theory (DFT) calculations. The Au/SiO 2 catalysts are less active for CO oxidation than the prototypical Au/TiO 2 catalysts, however they can be regenerated far more easily, allowing the activity of a catalyst to be fully recovered after deactivation.

In this paper we describe the production and investigation of two supported gold catalyst systems prepared by magnetron sputtering: Au on WO3 and Au on activated carbon. The magnetron sputtering technique entails using an argon plasma to sputter a high purity gold target producing a flux of gold atoms which are deposited onto a constantly tumbling support material. This technique offers a number of advantages over conventional chemical preparation methods. One advantage is the ability to create gold nanoparticles (diameters

This paper describes a one-step magnetron sputtering technique for the preparation of supported catalyst particles that has a number of advantages over existing methods. In order to demonstrate the effectiveness of this technique, a supported gold on γ -Al 2 O 3 oxidation catalyst has been prepared. This catalyst is as active as catalysts prepared via traditional chemical methods for the oxidation of carbon monoxide (TOF 1.1 conversions/surface Au atom/second at 300 K and 16% CO/8% O 2 /He). Aberration-corrected scanning transmission electron microscopy demonstrates that this technique produces gold nanoparticles in a size range that is claimed in the literature to be most active (about 2 nm).

Sm2Mo2O3.83N3.17, the first molybdenum oxynitride pyrochlore, was synthesized by heating the Sm2Mo2O7 pyrochlore in flowing ammonia at 625°C for 24 hours. Sm2Mo2O3.83N3.17 forms with the cubic pyrochlore structure, space group Fd3m (a = 10.4975 A). The sample is semiconducting and the temperature-dependent magnetic susceptibility follows Curie-Weiss behavior. X-ray absorption near-edge spectroscopy measurements indicate that in the oxynitride, molybdenum has a formal oxidation state significantly larger than 4+.

The SrMn1−xFexO3−δ (x=1/3, 1/2, 2/3) phases have been prepared and are shown by powder X-ray and neutron (for x=1/2) diffraction to adopt an ideal cubic perovskite structure with a disordered distribution of transition-metal cations over the six-coordinate B-site. Due to synthesis in air, the phases are oxygen deficient and formally contain both Fe3+ and Fe4+. Magnetic susceptibility data show an antiferromagnetic transition at 180 and 140 K for x=1/3 and 1/2, respectively and a spin-glass transition at 5, 25, 45 K for x=1/3, 1/2 and 2/3, respectively. The magnetic properties are explained in terms of super-exchange interactions between Mn4+, Fe(4+δ)+ and Fe(3+e)+. The XAS results for the Mn-sites in these compounds indicate small Mn-valence changes, however, the Mn-pre-edge spectra indicate increased localization of the Mn-eg orbitals with Fe substitution. The Mossbauer results show the distinct two-site Fe(3+e)+/Fe(4+δ)+ disproportionation in the Mn- substituted materials with strong covalency effects at both sites. This disproportionation is a very concrete reflection of a localization of the Fe-d states due to the Mn-substitution.

We have prepared a series of Mn substituted strontium ferrates, Sr 3 Fe 2− x Mn x O 7− δ where x =2/3, 1 and 4/3, and investigated their properties with X-ray diffraction, X-ray absorption near edge spectroscopy (XANES), Mossbauer spectroscopy, variable-temperature resistivity and magnetic susceptibility. These compounds are metastable and have to be prepared at high temperatures, >1250°C, with solid state techniques followed by quenching in air to room temperature. As a consequence the compounds are oxygen deficient and contain some Fe 3+ . They are insulators and exhibit spin-glass like behavior at low temperatures due to frustrated magnetic interactions between the disordered array of transition metal ions on the B site. Mossbauer and XANES spectra show that the B cations are not fully oxidized and that the Fe 4+ in these compounds are charge-disproportionated into Fe 3+ and Fe 5+ at low temperature.

We have prepared a series of Fe-substituted Sr 4 Mn 3− x Fe x O 10− δ strontium manganates with x =1, 3/2, and 2. These compounds adopt the n =3 Ruddlesden–Popper structure ( I 4/ mmm ), unlike the parent compound Sr 4 Mn 3 O 10 , which contains a network of face-sharing MnO 6 octahedra, with the larger Fe ion preferentially occupying the Mn/Fe (1) middle layer of the corner-sharing trioctahedra slabs. We have investigated their physical properties with X-ray diffraction, X-ray absorption near edge spectroscopy, Mossbauer spectroscopy, variable temperature resistivity, and magnetic susceptibility. In addition, for the x =2 compound we preformed room temperature neutron diffraction experiments. These compounds need to be formed at high temperatures; as a consequence they are oxygen deficient and contain some Fe 3+ . They are insulators and exhibit spin-glass-like transitions at low temperature.

We present here the synthesis, crystal structure, and physical properties of a reduced niobium oxide Sr0.93(SixNb1−x)Nb10O19 (x=0.87). Its structure was determined on single crystal by X-ray diffraction in the space group R3 (ah=7.843(1), ch=42.26(2) A, Vh=2251.3(9) A3, and Z=6). The compound is isostructural to Na(SixNb1−x)Nb10O19 (x≈0.75) and exhibits discrete [Nb6O12] clusters, Nb2O10 dimers, NbO6 octahedra, SrO12 cubo-octahedra, and SiO4 tetrahedra. The compound is insulating with a room-temperature resistivity ∼50 Ω cm. The magnetic susceptibility data yields μeff=3.16 μB/Nb, which is consistent with a 15-electron [Nb6O12] cluster, with Nb(IV) in the dimers and Nb(V) in the isolated NbO6 octahedra.