Fritz Haber Institute of the Max Planck Society

About: Fritz Haber Institute of the Max Planck Society is a facility organization based out in Berlin, Germany. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 3490 authors who have published 5017 publications receiving 183731 citations. The organization is also known as: Fritz Haber Institute of the Max Planck Society.

On the Power-Characteristics of Electrochemical Solar Cells

Abstract: The output-power-characteristics of an electrochemical solar cell are analysed. Up to 9.5% efficiency with reference to the spectrum of a Xenon lamp has been reached with a CdS/[Fe(CN)6]3-/4--electrolyte cell which is equivalent to 5.5% efficiency for solar radiation. It is shown that the polarisation of the inert counter electrode and the semiconductor electrode has a critical influence on the efficiency and can lead to great losses. Die Leistungscharakteristik einer elektrochemischen Sonnenzelle wurde untersucht. Bezogen auf das Spektrum einer Xenon-Lampe konnte mit einer CdS/[Fe(CN)6]3-/4--Redox-Elektrolytzelle eine maximale Energiewandlung von 9,5% erreicht werden. Das entspricht einer Ausbeute von 5,5% fur das Sonnenspektrum. Es wird gezeigt, das die Polarisation der Gegenelektrode und der Halbleiterelektrode einen kritischen Einflus auf die Leistungsfahigkeit hat. Bei hoher Polarisierbarkeit der Elektroden entstehen an den Phasengrenzen grose Verluste.

Electrolytic Growth and Dissolution of Oxide Layers on Silicon in Aqueous Solutions of Fluorides

Abstract: The growth and dissolution of oxide layers on silicon has been studied under illumination and in the dark by analyzing current transients at different voltages in solutions of NH4F of various concentrations at pH values between 1 and 4.5. When the oxidation rate of the silicon at high enough anodic bias and, for n-type specimens, high enough illumination intensity exceeds the rate of oxide dissolution in the fluoride, the film grows until it has reached a thickness where the dissolution is rate-determining for the net process. At higher voltages the current begins to oscillate. The data give some insight into the composition of the oxide layers and their electronic and ionic properties.

Role of Composition and Size of Cobalt Ferrite Nanocrystals in the Oxygen Evolution Reaction

Abstract: Sub-10 nm CoFe2O4 nanoparticles with different sizes and various compositions obtained by (partial) substitution of Co with Ni cations have been synthesized by using a one-pot method from organic solutions by the decomposition of metal acetylacetonates in the presence of oleylamine. The electrocatalytic activity of CoFe2O4 towards the oxygen evolution reaction (OER) is clearly enhanced with a smaller size (3.1 nm) of the CoFe2O4 nanoparticles (compared with 4.5 and 5.9 nm). In addition, the catalytic activity is improved by partial substitution of Co with Ni, which also leads to a higher degree of inversion of the spinel structure. Theoretical calculations attribute the positive catalytic effect of Ni owing to the lower binding energy differences between adsorbed O and OH compared with pure cobalt or nickel ferrites, resulting in higher OER activity. Co0.5Ni0.5Fe2O4 exhibited a low overpotential of approximately 340 mV at 10 mA cm−2, a smaller Tafel slope of 51 mV dec−1, and stability over 30 h. The unique tunability of these CoFe2O4 nanocrystals provides great potential for their application as an efficient and competitive anode material in the field of electrochemical water splitting as well as for systematic fundamental studies aiming at understanding the correlation of composition and structure with performance in electrocatalysis.

Structural, electronic, and magnetic properties of a ferromagnetic semiconductor: Co-doped TiO 2 rutile

Abstract: The local environment around magnetic impurity atoms was reported to be unchanged in a structural phase transition of nanocrystalline Co-doped ferromagnetic ${\mathrm{TiO}}_{2}.$ Our ab initio density functional theory investigations show that the substitutional Co ions incorporated into ${\mathrm{TiO}}_{2}$ rutile tend to cluster, and then the neighboring interstitial sites become energetically favorable for Co to reside. This suggests that a Co-doped rutile containing only substitutional Co may not be an appropriate reference bulk system in determining the local environment of Co in polycrystalline $(\mathrm{T}\mathrm{i},\mathrm{C}\mathrm{o}){\mathrm{O}}_{2}$ rutile. We also find that the interstitial Co is in the low spin state and destroys the spin polarization of the surrounding substitutional Co, and hence reduces the average magnetic moment of impurity atoms.

Interaction of Probe Molecules with Bridging Hydroxyls of Two-Dimensional Zeolites: A Surface Science Approach

Abstract: Bridging hydroxyls (Si–OH–Al) in zeolites are catalytically active for a multitude of important reactions, including the catalytic cracking of crude oil, oligomerization of olefins, conversion of methanol to hydrocarbons, and the selective catalytic reduction of NOx. The interaction of probe molecules with bridging hydroxyls was studied here on a novel two-dimensional zeolite model system consisting of an aluminosilicate forming a planar sheet of polygonal prisms, supported on a Ru(0001) surface. These bridging hydroxyls are strong Bronsted acid sites and can interact with both weak and strong bases. This interaction is studied here for two weak bases (CO and C2H4) and two strong bases (NH3 and pyridine), by infrared reflection absorption spectroscopy, in comparison with density functional theory calculations. Additionally, ethene is the reactant in the simplest case of the olefin oligomerization reaction which is also catalyzed by bridging hydroxyls, making the study of this adsorbed precursor state part...