Interactions of Au cluster anions with oxygen

Experimental and theoretical evidence is presented for the nondissociative chemisorption of O2on free Au cluster anions (Au−n, n=number of atoms) with n=2, 4, 6 at room temperature, indicating that the stabilization of the activated di-oxygen species is the key for the unusual catalytic activities of Au-based catalysts. In contrast to Au−n with n=2, 4, 6, O2 adsorbs atomically on Aumonomer anions. For the Aumonomer neutral, calculations based on density functional theory reveal that oxygen should be molecularly bound. On Au dimer and tetramer neutrals, oxygen is molecularly bound with the O–O bond being less activated with respect to their anionic counterparts, suggesting that the excess electron in the anionic state plays a crucial role for the O–O activation. We demonstrate that interplay between experiments on gas phase clusters and theoretical approach can be a promising strategy to unveil mechanisms of elementary steps in nanocatalysis

Photoelectron spectroscopic and theoretical study of the [HPd(η(2)-H2)](-) cluster anion.

Anion photoelectron spectroscopic and theoretical studies were conducted for the PdH(-) and PdH3 (-) cluster anions. Experimentally observed electron affinities and vertical detachment energies agree well with theoretical predictions. The PdH3 (-) anionic complex is made up of a PdH(-) sub-anion ligated by a H2 molecule, in which the H-H bond is lengthened compared to free H2. Detailed molecular orbital analysis of PdH(-), H2, and PdH3 (-) reveals that back donation from a d-type orbital of PdH(-) to the σ* orbital of H2 causes the H-H elongation, and hence, its activation. The H2 binding energy to PdH(-) is calculated to be 89.2 kJ/mol, which is even higher than that between CO and Pd. The unusually high binding energy as well as the H-H bond activation may have practical applications, e.g., hydrogen storage and catalysis

Kritische Betrachtung zum Klimaschutz

Kritische Betrachtung zum Klimaschutz: Die internationale Staatengemeinschaft bemüht sich um eine Reduktion der Treibhausgasemissionen. Auch Deutschland beteiligt sich an diesen Anstrengungen, hat sich aber mit der "Energiewende" für einen Sonderweg entschieden, der zunehmend zu einem Problem wird. Durch die deutsche Subventionspolitik kommt es zu einer Stromüberproduktion, die die Existenz von Gas- und Wasserkraftwerken gefährdet, die eigentlich dringend für die Energiewende benötigt werden. Gleichzeitig kann trotz des enormen Ausbaus von Wind- und Solarkraftwerken nicht auf die klimaschädlichen Braunkohlekraftwerke verzichtet werden, da sonst in windstillen Nächten Stromausfälle drohen. Die Erfolgsmeldungen über die deutsche Energiewende sind irreführend, denn sie beziehen sich nur auf die Stromproduktion. Bei der Gesamtenergie liegt der Anteil der fossilen Energien mit 80% immer noch ziemlich genau im globalen Durchschnitt. Der Anbau von Energiepflanzen im Rahmen der Energiewende führt sogar zu erhöhten Methanemissionen. Aus diesen Gründen wird die deutsche Energiewende ihre selbstgesetzten Ziele für das Jahr 2020 nicht erreichen. Hinzu kommt, daß das Erneuerbare-Energie-Gesetz (EEG) die Bemühungen der EU unterläuft, mittels CO2-Zertifikaten die Emissionen zu reduzieren. Eine Reform des EEG ist dringend notwendig. Critical point of view on climate protection: The international community is working to reduce the greenhouse gas emissions. Germany participates in these efforts, but with the »Energiewende« it has chosen a different route than any other country. This is increasingly becoming a problem. The German subsidy policy leads to frequent overproduction of electricity. This makes the operation of gas and hydroelectric power plants unprofitable and some have already been shut down. However, these power plants are urgently needed for the energy transition. At the same time, despite the enormous expansion of wind and solar power plants, the climate-damaging lignite power plants cannot be shut down, because otherwise there would be blackouts in windless nights. In addition, the success stories about the German energy transition are misleading as they only relate to electricity production. The contribution of fossil fuels to the total energy is 80%, which is almost exactly the global average. The cultivation of energy crops as part of the energy transition even leads to increased methane emissions. For these reasons, the German »Energiewende« will not reach its self-imposed goals for the year 2020. In addition, the German Renewable Energy Law (EEG) undermines the EU‘s efforts to reduce emissions with the method of CO2 certificates. A reform of the EEG is urgently needed

Localization of 3 d and 4 d electrons in small clusters : the roots of magnetism

The photoelectron spectra of mass-selected negatively charged Nin- and Cun- clusters show similarities, which indicate an almost total localization of the Ni 3d orbitals corresponding to a maximum magnetic moment of 1μB per Ni atom. The similarity between Nin- and Cun- vanishes for n>7 corresponding to an increase in 3d delocalization. The data of Pdn- clusters suggest a Ni-like ( magnetic ) electronic structure for n = 3 6 and a Pt-like ( nonmagnetic ) one for n>15. There are indications that neutral Pd7 is a closed shell species (spin zero ground state)

Shell structure and s-p hybridization in small aluminum clusters

Photoelectron spectra of Al−n (n=2 20) clusters are presented. Due to the improved energy resolution and the relatively high photon energy (hv=6.424 eV, ArF laser radiation) available in our experiment the spectra reveal the mechanism of the onset of the s p hybridization occuring in these particles. Between Al−6 Al−12 a mixing of the uppermost antibonding 3s derived orbital with the 3p band takes place which is observed simultaneously with the 2D→3D structural transition predicted for Al clusters in this size range. Starting from Al−13 a pattern resembling an electronic shell structure is identified

Formation of di-oxygen species on Ag anion clusters

Experiments using vibrationally resolved ultraviolet photoelectron spectroscopy show that oxygen selectively adsorbs on even-numbered Ag anion clusters, whereas the odd-numbered clusters are not chemically active. We provide evidence that O2 molecularly adsorbs on Ag anion clusters consisting of less than 15 atoms. O2 adsorption pattern for Ag anion clusters is quite analogous to that of Au anion clusters. We suggest that for the reactions efficiently catalyzed by Au-nanocatalysts, Ag nanoclusters can be a promising candidate as a building block of catalysts