Käfigtransport: Die Aufnahme von H2‐Molekülen in H2O‐Käfige unter Bildung von Wasserstoff‐Clathrat‐Hydraten eröffnet neue Möglichkeiten für die Speicherung und den Transport von Wasserstoff. Reine H2‐Cluster lassen sich jedoch nur unter hohem Druck im Clathrat‐Hydrat stabilisieren. Abhilfe schafft die Einführung von THF als zweitem Gastmolekül, das den erforderlichen Druck von 220 MPa auf 5 MPa verringert (Bild: H2/THF‐Hydrat; blau THF, rot H2).

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Atomically dispersed metal catalysts anchored on nitrogendoped (N-doped) carbons demand attention due to their superior catalytic activity relative to that of metal nanoparticle catalysts in energy storage and conversion processes. Herein, we introduce a simple and versatile strategy for the synthesis of hollow N-doped carbon capsules that contain one or more atomically dispersed metals (denoted as H−M−N x −C and H−M mix −N x −C, respectively, where M = Fe, Co, or Ni). This method utilizes the pyrolysis of nanostructured core−shell precursors produced by coating a zeolitic imidazolate framework core with a metal−tannic acid (M−TA) coordination polymer shell (containing up to three different metal cations). Pyrolysis of these core−shell precursors affords hollow N-doped carbon capsules containing monometal sites (e.g., Fe−N x , CoN x , or Ni−N x ) or multimetal sites (Fe/Co−N x , Fe/Ni−N x , Co/Ni−N x , or Fe/Co/Ni−N x ). This inventory allowed exploration of the relationship between catalyst composition and electrochemical activity for the oxygen reduction reaction (ORR) in acidic solution.and H−FeCoNi−N x −C were particularly efficient ORR catalysts in acidic solution. Furthermore, the H− Fe−N x −C catalyst exhibited outstanding initial performance when applied as a cathode material in a proton exchange membrane fuel cell. The synthetic methodology introduced here thus provides a convenient route for developing nextgeneration catalysts based on earth-abundant components.

The use of flowing electrochemical reactors, for example, in redox flow batteries and in various electrosynthesis processes, is increasing. This technology has the potential to be of central significance in the increased deployment of renewable electricity for carbon-neutral processes. A key element of optimizing efficiency of electrochemical reactors is the combination of high solution conductivity and reagent solubility. Here, we show a substantial rate of charge transfer for an electrochemical reaction occurring in a microemulsion containing electroactive material is loaded inside the nonpolar (toluene) subphase of the microemulsion. The measured rate constant translates to an exchange current density comparable to that in redox flow batteries. The rate could be controlled by the surfactant, which maintains partitioning of reactants and products by forming an interfacial region with ions in the aqueous phase in close proximity. The hypothesized mechanism is evocative of membrane-bound enzymatic reactions. Achieving sufficient rates of electrochemical reaction is the product of an effort designed to establish a reaction condition that meets the requirements of electrochemical reactors using microemulsions to realize a separation of conducting and reactive elements of the solution, opening a door to the broad use of microemulsions to effect controlled electrochemical reactions as steps in more complex processes.

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Supportless platinum nanotubes (PtNTs) were synthesized by the decomposition of platinum acetylacetonate vapor within anodic alumina templates at 210 • C. As synthesized, the nanotubes are nanoparticulate aggregates composed of Pt crystallites approximately 3 nm in diameter and with a range of lengths from 1 μm to 20 μm. Annealing treatments result in crystallite growth and morphological evolution of the tubular nanostructures including the development of nanoscale porosity. In rotating disk electrode measurements carried out in 0.1 M HClO 4 , porous PtNTs annealed at 500 • C exhibited a specific activity for oxygen reduction of 2390 ± 423 μA/cm 2 Pt at 0.9 V, comparable to bulk polycrystalline Pt. The electrochemical surface area of the annealed structures was a relatively low 10 m 2 /g, resulting in a moderate overall mass activity of 240 ± 41 mA/mg Pt .

In this work, the properties of univalent, that is, Li+, Na+, NH4 +, and TEA+ form perfluorosulfonate (PFSA) membranes are studied and compared to the properties of H+ form materials. Properties of these polymer membranes including water uptake, density and conductivity, were investigated for membranes exposed to various water activity levels. The water uptake by the membranes decreased in the order H+ > Li+ > Na+ > NH4 + > TEA+, the same order as the hydration enthalpy (absolute values) of cations. Conductivity values did not strictly follow this order, indicating the importance of different factors besides the hydration level. The partial molar volume of water is derived from the density data as a function of water content for the various membrane forms. This provides further insight into the water, cation, and polymer interactions. Factors that contribute to the conductivity of these membranes include the size of cations, the electrostatic attraction between cations and sulfonate group, and the ion-dipole and hydrogen bonding interactions between cations and water. NH4 + transport is surprisingly high given the low water uptake in NH4 + form membranes. We attribute this to the ability of this ion to develop hydrogen bonded structures that helps to overcome electrostatic interactions with sulfonates. Pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) was used to measure the diffusion coefficient of water in the membranes. FT-IR spectroscopy is employed to probe cation interactions with water and sulfonate sites in the polymer. Overall, the results reflect a competition between the strong electrostatic interaction between cation and sulfonate versus hydration and hydrogen bonding which vary with cation type.

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