A lithium metal all-solid-state battery with excellent rate capability up to 10 mA cm−2 is realized by our mechanical constriction design for kinetically limited reduction pathways.

No abstract

For fuel-cell applications, ethanol is becoming a more attractive fuel than methanol or hydrogen because it has higher mass energy density and can be produced in great quantities from biomass.[1] Additionally, ethanol is less toxic than methanol and easier to handle than hydrogen. [2,3] However, the C À C bond in ethanol leads to more complicated reaction intermediates and products during oxidation, [2][3][4][5][6][7][8][9][10][11][12] and catalysts must be able to activate C À C bond scission for complete oxidation to CO 2 . Consequently, much effort has been made to investigate the reaction mechanisms of direct ethanol fuel cells (DEFCs) with various analytical methods. [2][3][4][5][6][7][8][9][10][11][12] Especially the intermediates and products that are generated during the electrochemical reaction at different ethanol concentrations and potentials have been investigated and quantified by chromatographic techniques, [4][5][6] infrared reflectance spectroscopy (IRS), [4,[6][7][8][9] and differential electrochemical mass spectrometry (DEMS). [8][9][10] These studies revealed that most of the ethanol was oxidized to acetic acid (AA) or acetaldehyde (AAL) on Pt, but not much to CO 2 . Additionally, investigations of ethanol oxidation on various catalysts showed that alloying Pt with other transition elements improves the catalytic activity. [6,10,12,13] However, DEMS is limited to the detection of volatile chemicals, and IRS requires smooth electrodes with sufficient reflectivity. On the other hand, liquid-state nuclear magnetic resonance (NMR) spectroscopy is a straightforward analytical method which can be applied to an operating fuel cell without any modification. [14] In liquid-state NMR spectroscopy, peak areas are linearly proportional to the abundance of chemical species that are identifiable by their chemical shifts. The DEFC anode exhaust has been shown to give well-resolved 13 C peaks that can unambiguously identify chemical species.[14] We have used 13 C liquid-state NMR spectroscopy to identify and quantify the reaction products present in the liquid anode exhaust of DEFCs that were operated with three different anode catalysts at various potentials. The results were used to explain the effect of elements such as Ru and Sn on the Pt/C anode catalyst and to propose reaction mechanisms of ethanol on Pt-based catalysts.The 13 C liquid-state NMR experiments were performed on DEFCs containing 40 wt % Pt/C, PtRu/C, or Pt 3 Sn/C anode catalysts prepared by a polyol method. Full experimental details are described in the Supporting Information. Figure 1 shows the 13 C NMR spectra of the anode exhaust from the DEFCs with Pt 3 Sn/C anode catalysts. The spectra were expanded in the y scale while maintaining the relative peak heights. The chemical species were assigned to the peaks in the spectrum according to literature data, [15] and C atoms that are responsible for 13 C NMR signals are underlined. In the exhaust, the dominant reaction products were AAL (d = 207 ppm), AA (d = 177 ppm), and ethane-1,1-diol (ED, ...

A composite of modified graphene and LiFePO4 has been developed to improve the speed of charging-discharging and the cycling stability of lithium ion batteries using LiFePO4 as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO4 to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO4 composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO4 composite as a cathode active material. Interestingly, the CA-graphene/LiFePO4 composite has exhibited better electrochemical properties than the conventional graphene/LiFePO4 composite as well as bare LiFePO4, including exceptional speed of charging-discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO4 particles. Owing to these properties of CA-graphene, LiFePO4 could demonstrate enhanced and stably long-lasting electrochemical performance.

The effect of strain on the cation interdiffusion in InGaAs/GaAs quantum wells is described. It is found that the Fick’s diffusion equation does not properly describe the interdiffusion in the heterostructure with strained layers. It is believed that the strain changes crystal defect concentration and thus diffusivity is influenced by strain. Diffusion equation including the strain effect is formulated and solved numerically. The experimental photoluminescence peak shifts as a function of annealing time are well-fitted by this analysis and useful parameters such as diffusivity describing InGaAs/GaAs quantum well interdiffusion are extracted.

The conflicting interpretations (square vs. rhomboidal) of the recent experimental visualization of the two-dimensional (2D) water confined in between two graphene sheets by transmission electron microscopy measurements, make it important to clarify how the structure of twodimensional water depends on the constraining medium. Toward the end, we report here molecular dynamics (MD) simulations to characterize the structure of water confined in between two MoS 2 sheets. Unlike graphene, water spontaneously fills the region sandwiched by two MoS 2 sheets in ambient conditions to form planar multi-layered water structures with up to four layer. These 2D water molecules form a specific pattern in which the square ring structure is formed by four diamonds via H-bonds, while each diamond shares a corner in a perpendicular manner, yielding an intriguing isogonal tiling structure. Comparison of the water structure confined in graphene (flat uncharged surface) vs. MoS 2 (ratchet-profiled charged surface) demonstrates that the polarity (charges) of the surface can tailor the density of confined water, which in turn can directly determine the planar ordering of the multi-layered water molecules in graphene or MoS 2 . On the other hand, the intrinsic surface profile (flat vs. ratchet-profiled) plays a minor role in determining the 2D water configuration.

No abstract

Sixty-three percent of PEM fellowship programs integrate HFS-based activities. The majority of PEM fellowship program directors value the role of HFS in augmenting clinical experience and documenting procedural skills. Regional simulation centers are one possible solution to offer HFS training to fellowships with limited financial support and/or lack of experienced simulation faculty.