Scalable Synthesis of Multi-Metal Electrocatalyst Powders and Electrodes and their Application for Oxygen Evolution and Water Splitting

Multi-metal electrocatalysts provide nearly unlimited catalytic possibilities arising from synergistic element interactions. We propose a polymer/metal precursor spraying technique that can easily be adapted to produce a large variety of compositional different multi-metal catalyst materials. To demonstrate this, 11 catalysts were synthesized, characterized, and investigated for the oxygen evolution reaction (OER). Further investigation of the most active OER catalyst, namely CoNiFeMoCr, revealed a polycrystalline structure, and operando Raman measurements indicate that multiple active sites are participating in the reaction. Moreover, Ni foam-supported CoNiFeMoCr electrodes were developed and applied for water splitting in flow-through electrolysis cells with electrolyte gaps and in zero-gap membrane electrode assembly (MEA) configurations. The proposed alkaline MEA-type electrolyzers reached up to 3 A cm⁻², and 24 h measurements demonstrated no loss of current density of 1 A cm⁻².     

Electron transmission through organized organic thin films studied by discrete initial electron kinetic energies

Synchrotron radiation (SR) pulses are used to eject electrons from a gold substrate covered with organized organic thin films (OOTF) in order to investigate their transmission probability through the OOTF as a function of the electron initial kinetic energy. By variation of the SR photon energy within a few eV above the Au-4f binding energy levels we controlled the initial kinetic energy of the substrate electrons. The observed oscillations in the transmission probability for porphyrin-based films as a function of the kinetic energy is argued to be due to effects of band structure above the vacuum level in the well-ordered molecular adsorbate. We also present valence photoemission spectra (PES) of different type OOTF and demonstrate how their coverage of the substrate affects the PES. Received 24 July 1998     

The Equilibrium between Localized and Delocalized States of Thermochromic Semibullvalenes and Barbaralanes—Direct Observation of Transition States of Degenerate Cope Rearrangements

The UV/Vis spectra of thermochromic semibullvalenes 1 and barbaralanes recorded at various temperatures yield enthalpy differences between the two degenerate classical structures 1 and 1′ and the less stable species ( 1* ) that absorb at long wavelengths. The latter species are interpreted in terms of higher, delocalized states that are located just above the flat potential energy barrier between the ground states (ΔH⁰=11 (R=H; in butyronitrile), 1 kJ mol⁻¹ (R=Ph)).     

Pluriharmonic maps into Kähler symmetric spaces and Sym’s formula

A construction due to Sym and Bobenko recovers constant mean curvature surfaces in euclidean 3-space from their harmonic Gauss maps. We generalize this construction to higher dimensions and codimensions replacing the surface by a complex manifold and the sphere (the target space of the Gauss map) by a Kähler symmetric space of compact type with its standard embedding into the Lie algebra ${\mathfrak{g}}A construction due to Sym and Bobenko recovers constant mean curvature surfaces in euclidean 3-space from their harmonic Gauss maps. We generalize this construction to higher dimensions and codimensions replacing the surface by a complex manifold and the sphere (the target space of the Gauss map) by a K?hler symmetric space of compact type with its standard embedding into the Lie algebra \mathfrakg{\mathfrak{g}} of its transvection group. Thus we obtain a new class of immersed K?hler submanifolds of \mathfrakg{\mathfrak{g}} and we derive their properties.     

Solvent Effects on the Equilibrium between Localized and Delocalized States of Thermochromic Semibullvalenes and Barbaralanes

The position of the equilibrium between localized and delocalized states of thermochromic semibullvalenes and barbaralanes (see the Equation) depends strongly on the solvent. Dipolar aprotic solvents, particularly N,N′-dimethylpropylene urea, favor the delocalized, bishomoaromatic state (ΔH⁰=8 kJ mol⁻¹ (cyclohexane), ΔH⁰<0 kJ mol⁻¹ (N,N′-dimethylpropylene urea)).