Maurits W. E. van den Berg

Ruthenium Nanoparticles inside Porous [Zn4O(bdc)3] by Hydrogenolysis of Adsorbed [Ru(cod)(cot)]: A Solid-State Reference System for Surfactant-Stabilized Ruthenium Colloids

The gas-phase loading of [Zn4O(bdc)3] (MOF-5; bdc = 1,4-benzenedicarboxylate) with the volatile compound [Ru(cod)(cot)] (cod = 1,5-cyclooctadiene, cot = 1,3,5-cyclooctatriene) was followed by solid-state (13)C magic angle spinning (MAS) NMR spectroscopy. Subsequent hydrogenolysis of the adsorbed complex inside the porous structure of MOF-5 at 3 bar and 150 degrees C was performed, yielding ruthenium nanoparticles in a typical size range of 1.5-1.7 nm, embedded in the intact MOF-5 matrix, as confirmed by transmission electron microscopy (TEM), selected area electron diffraction (SAED), powder X-ray diffraction (PXRD), and X-ray absorption spectroscopy (XAS). The adsorption of CO molecules on the obtained Ru@MOF-5 nanocomposite was followed by IR spectroscopy. Solid-state (2)H NMR measurements indicated that MOF-5 was a stabilizing support with only weak interactions with the embedded particles, as deduced from the surprisingly high mobility of the surface Ru-D species in comparison to surfactant-stabilized colloidal Ru nanoparticles of similar sizes. Surprisingly, hydrogenolysis of the [Ru(cod)(cot)]3.5@MOF-5 inclusion compound at the milder condition of 25 degrees C does not lead to the quantitative formation of Ru nanoparticles. Instead, formation of a ruthenium-cyclooctadiene complex with the arene moiety of the bdc linkers of the framework takes place, as revealed by (13)C MAS NMR, PXRD, and TEM.

A colloidal ZnO/Cu nanocatalyst for methanol synthesis

Free-standing, ZnO surface decorated Cu nanoparticles of 1-3 nm size were obtained by sequential co-pyrolysis of [Cu(OCHMeCH2NMe2)2] and ZnEt2 in squalane in the absence of additional surfactants and proved to be highly active quasi homogeneous catalysts for methanol synthesis from CO and H2.

Nano-brass colloids: synthesis by co-hydrogenolysis of [CpCu(PMe3)] with [ZnCp*2] and investigation of the oxidation behaviour of α/β-CuZn nanoparticles

A novel, non-aqueous organometallic access to colloidal copper and copper/zinc (brass) nanoparticles is described. Hydrogenolysis of the precursor [CpCu(PMe3)] (1) in mesitylene at 150 °C and 3 bar H2 quantitatively gives elemental Cu. Analogously, a solution of [ZnCp*2] (2) reacts with H2 to give elemental Zn in 100% yield. Co-hydrogenolysis of 1 and 2 in exactly equimolar quantities selectively yields the intermetallic phase β-CuZn characterised by powder X-ray diffraction (PXRD). Deep red colloidal solutions of nano-Cu as well as red to violet colloids of nano-brass alloys (α/β-CuZn) are obtained by co-hydrogenolysis of 1 and 2 in the presence of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as surfactant. All samples of the general formula Cu1−xZnx (0.09 ≤ x ≤ 0.50) were characterised by means of elemental analysis, PXRD, transmission electron microscopy (TEM, EDX and SAED) and UV-Vis absorption spectroscopy. The presence and alloying of metallic Cu and Zn in the β-CuZn sample as a representative example of the series was confirmed by extended X-ray absorption fine structure spectroscopy (EXAFS). The oxidation behaviour of the nanoparticles was investigated by EXAFS, PXRD and UV-Vis spectroscopy indicating, that CuOx@Cu core–shell type particles were formed for pure copper particles, while in the case of brass particles preferential oxidation of the Zn component takes place, which results in core–shell particles of the type (ZnO)δ@Cu1−xZnx−δ.

A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests.

A test setup for membrane-electrode-assemblies (MEAs) of proton exchange membrane fuel cells which allows in situ fluorescence x-ray absorption spectroscopy studies of one electrode with safe exclusion of contributions from the counter electrode is described. Interference by the counter electrode is excluded by a geometry including a small angle of incidence (< 6°) between primary beam and electrode layer. The cell has been constructed by introducing just minor modifications to an electrochemical state-of-the-art MEA test setup, which ensures realistic electrochemical test conditions. This is at the expense of significant intensity losses in the path of the incident beam, which calls for the brilliance of third-generation synchrotrons to provide meaningful data. In measurements on Pt∕C and Pt-Co∕C cathodes combined with Pt-C anodes (H(2)/O(2) feed), good data quality was demonstrated both for the majority element Pt as well as for Co despite of a low areal Co density in the order of 0.02 mg/cm(2).