Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

Nanostructured materials have shown extraordinary promise for electrochemical energy storage but are usually limited to electrodes with rather low mass loading (~1 milligram per square centimeter) because of the increasing ion diffusion limitations in thicker electrodes. We report the design of a three-dimensional (3D) holey-graphene/niobia (Nb2O5) composite for ultrahigh-rate energy storage at practical levels of mass loading (>10 milligrams per square centimeter). The highly interconnected graphene network in the 3D architecture provides excellent electron transport properties, and its hierarchical porous structure facilitates rapid ion transport. By systematically tailoring the porosity in the holey graphene backbone, charge transport in the composite architecture is optimized to deliver high areal capacity and high-rate capability at high mass loading, which represents a critical step forward toward practical applications.

Three-dimensional holey-graphene/niobia composite architectures for ultrahigh-rate energy storage

Three-Dimensional Holey-Graphene/Niobia Composite Architectures for Ultrahigh-Rate Energy Storage

ConspectusSince the first report on the long-term durable 9.7% solid-state perovskite solar cell employing methylammonium lead iodide (CH3NH3PbI3), mesoporous TiO2, and 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-MeOTAD) in 2012, following the seed technologies on perovskite-sensitized liquid junction solar cells in 2009 and 2011, a surge of interest has been focused on perovskite solar cells due to superb photovoltaic performance and extremely facile fabrication processes. The power conversion efficiency (PCE) of perovskite solar cells reached 21% in a very short period of time. Such an unprecedentedly high photovoltaic performance is due to the intrinsic optoelectronic property of organolead iodide perovskite material. Moreover, a high dielectric constant, sub-millimeter scale carrier diffusion length, an underlying ferroelectric property, and ion migration behavior can make organolead halide perovskites suitable for multifunctionality. Thus, besides solar cell applicati...

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Lewis Acid-Base Adduct Approach for High Efficiency Perovskite Solar Cells.

Metal-based reactive nanomaterials

An exact derivation of the Scherrer equation is given for particles of spherical shape, values of the constant for half-value breadth and for integral breadth being obtained. Various approximation methods which have been used are compared with the exact calculation. The tangent plane approximation of v. Laue is shown to be quite satisfactory, but some doubt is cast on the use of approximation functions. It is suggested that the calculation for the ellipsoidal particle based on the tangent plane approximation will provide a satisfactory basis for future work.

The Scherrer Formula for X-Ray Particle Size Determination

The problem of the diffraction of x-rays by small crystalline particles is discussed by the methods of Fourier analysis, and the calculation of the intensity of the x-ray scattering from a single particle is reduced to the evaluation of a simple Fourier transform. This approach leads immediately to the interference functions for the parallellepipedon and the octahedron as obtained by other authors. In addition, it makes possible the detailed discussion of the interference functions for the tetrahedron, the rhombic dodecahedron, the ellipsoid, and the elliptic cylinder. The method is shown to be applicable to any polyhedron. A simple method is also given for calculating the interference function and its integral breadth for specific directions of departure from the whole-numbered points. This is applied to obtain a partial discussion of the scattering from the tetrahexahedron and the trisoctahedron.

A. L. Patterson

Papers

The Scherrer Formula for X-Ray Particle Size Determination

The Diffraction of X-Rays by Small Crystalline Particles