Catalysis in General Energy Research

For the storage of hydrogen in the form of synthetic liquid fuels, the reversible catalytic hydrogenation of toluene, and the catalytic hydrogenation of CO2 yielding MeOH, are investigated. Catalytic processes are important in electrochemistry and, in particular, in the realization of electrodes with high power densities for low-temperature polymer electrolyte fuel cells. As a third area where catalysis is assigned a crucial role within General Energy Research, the treatment of exhaust gases from combustion processes will be discussed

Kinetics and Mechanism of Metal Nanoparticle Growth via Optical Extinction Spectroscopy and Computational Modeling: The Curious Case of Colloidal Gold

An overarching computational framework unifying several optical theories to describe the temporal evolution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we used the inexpensive and widely available optical extinction spectroscopy, to obtain quantitative kinetic data. In situ spectra collected over a wide set of experimental conditions were regressed using the physical model, calculating light extinction by ensembles of GNPs during the growth process. This model provides temporal information on the size, shape, and concentration of the particles and any electromagnetic interactions between them. Consequently, we were able to describe the mechanism of GNP growth and divide the process into distinct genesis periods. We provide explanations for several longstanding mysteries, for example, the phenomena responsible for the purple-greyish hue during the early stages of GNP growth, the complex interactions between nucleation, growth, and aggregation events, and a clear distinction between agglomeration and electromagnetic interactions. The presented theoretical formalism has been developed in a generic fashion so that it can readily be adapted to other nanoparticulate formation scenarios such as the genesis of various metal nanoparticles.Comment: Main text and supplementary information (accompanying MATLAB codes available on the journal webpage

Influence of Potassium Doping on the Activity and the Sulfur Poisoning Resistance of Soot Oxidation Catalysts

Soot oxidation on potassium nitrate impregnated cerium oxide and manganese cerium mixed oxide was investigated using TG-FTIR. It was found, that potassium nitrate promotes the soot oxidation by enhancing the contact between the soot and the catalyst, as soot ignition temperature corresponds to the melting point of potassium nitrate for both the individual and the mixed oxide. Since potassium nitrate is easier sulfatized than cerium or manganese, the susceptibility of the catalyst to sulfur poisoning is considerably decrease

Catalytic investigation of Fe-ZSM5 in the selective catalytic reduction of NOxwith NH3

Summary: Fe-ZSM5 coated on a cordierite monolith was characterized and tested in the selective reduction of nitrogen oxides (NOx) with ammonia. More than 70 % of the NOxwere converted at T>350 °C if only NO was present in the feed. For equimolar amounts of NO and NO2in the feed, NOxconversions of over 90 % were reached for T = 200-450 °C. Hydrothermal ageing of Fe-ZSM5 resulted in a small loss in NOxconversion and enhanced N2O formatio

Nickel Deposition on ?-Al2O3: Modelling Metal Particle Behaviour at the Support

Recently, surface modifications on a commercial Ni/Al2O3 catalyst during the production of methane from synthesis gas were investigated by quasi in situ X-ray photoelectron spectroscopy (XPS). The effect of the synthesis gas on the surface properties of the catalyst and on its activity under methanation conditions was studied on an atomic level. The conclusion was that the stability of Ni particles on the ?-Al2O3 support can be influencedby cluster growth phenomena, which influence both size and distribution of the metal particles. In this study, Ni deposition and cluster growth on model catalyst samples (10 nm thick, polycrystalline ?-Al2O3 on Si(100)) was investigated by XPS. The molecular structure of the catalyst was investigated using Density Functional Theory calculations (StoBe) with cluster model and non-local functional (RPBE) approach. Al15O40H35 clusterswere selected to represent the ?-Al2O3 (100) surface. Ni clusters of different size were cut from a Ni(100) surface and deposited on the Al15O40H35 cluster in order to validate the deposition model determined by XPS

Laser induced forward transfer of SnO2 for sensing applications using different precursors systems

This paper presents the transfer of SnO2 by laser induced forward transfer (LIFT) for gas sensor applications. Different donor substrates of SnO2 with and without triazene polymer (TP) as a dynamic release layer were prepared. Transferring these films under different conditions were evaluated by optical microscopy and functionality. Transfers of sputtered SnO2 films do not lead to satisfactory results and transfers of SnO2 nanoparticles are difficult. Transfers of SnO2 nanoparticles can only be achieved when applying a second laser pulse to the already transferred material, which improves the adhesion resulting in a complete pixel. A new approach of decomposing the transfer material during LIFT transfer was developed. Donor films based on UV absorbing metal complex precursors namely, SnCl2(acac)2 were prepared and transferred using the LIFT technique. Transfer conditions were optimized for the different systems, which were deposited onto sensor-like microstructures. The conductivity of the transferred material at temperatures of about 400∘C are in a range usable for SnO2 gas sensors. First sensing tests were carried out and the transferred material proved to change conductivity when exposed to ethanol, acetone, and methan

Novel ETFE based radiation grafted poly(styrene sulfonic acid-co-methacrylonitrile) proton conducting membranes with increased stability

Styrene radiation grafted ETFE based proton conducting membranes are subject to degradation under fuel cell operating conditions and show a poor stability. Lifetimes exceeding 250 h can only be achieved with crosslinked membranes. In this study, a novel approach based on the increase of the intrinsic oxidative stability of uncrosslinked membranes is reported. Hence, the co-grafting of styrene with methacrylonitrile (MAN), which possesses a protected α-position and strong dipolar pendant nitrile group, onto 25 μm ETFE base film was investigated. Styrene/MAN co-grafted membranes were compared to a styrene based membrane in durability tests in single H2/O2 fuel cells. It is shown that the incorporation of MAN considerably improves the chemical stability, yielding fuel cell lifetimes exceeding 1000 h. The membrane preparation based on the co-grafting of styrene and MAN offers the prospect of tuning the MAN content and introduction of a crosslinker to enhance the oxidative stability of the resulting fuel cell membranes