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Bioenergy and Catalysis Laboratory (LBK)

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Scientific Highlights

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Datum
5 September 2019
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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 volution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we sed 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 hysical model, calculating light extinction by ensembles of GNPs during the growth process. This model rovides 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, e.g., 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.

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29 June 2018
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Cleaner emissions thanks to sponge-like structure

Media Releases Energy and Climate

PSI researchers have developed a new catalytic converter for cleaning emissions from natural gas engines. It is very active even at low temperatures and remains that way over a long period of time. This allows natural gas to be burned in a cleaner, more climate-friendly way. Thus natural gas and biogas become more attractive as substitutes for petroleum products – for example, as fuel for cars.

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15 July 2012

Supported gold as catalyst for the decomposition of ammonia precursors in the selective catalytic reduction of NOx

Titaniumdioxide supported gold was found to catalyze the hydrolysis of formate-based ammonia precursor compounds which are proposed for the selective catalytic reduction of nitrogen oxides (NOx) in combustion exhaust gas. In contrast to other noble metals, the supported gold does not oxidize the released NH3, while it maintains decomposition of intermediate formic acid.

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20 September 2011
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Influence of Methyl Halide Treatment on Gold Nanoparticles Supported on Activated Carbon

Gold particles supported on carbon when subjected to a flow of methyl iodide or bromide redisperse from large ensembles to single atoms and/or dimers of gold. Methyl halide oxidizes gold leading to gradual particle dissolution. The process could be carried out at temperatures as low as 50 °C. The excess of halide could be removed by a post-treatment of the material with 1%H2O/H2, which does not influence the metal dispersion. This remarkable transformation opens the possibility of re-activating gold catalysts that lost their performance due to metal particles sintering.

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15 October 2007

Vibrational Spectra of Adsorbates from DFT

The hydrolysis of isocyanic acid was studied experimentally and theoretically and a reaction mechanism on different catalysts was established. The decreasing NOx emission limits for diesel vehicles impel the further development of the existing NOx deactivation technologies, particularly the selective catalytic reduction (SCR) of nitrogen oxides with urea. In the urea-SCR process, urea is injected into the hot exhaust gas, where it thermally decomposes into isocyanic acid (HNCO) and ammonia.

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Paul Scherrer Institut
Bioenergy and Catalysis Laboratory
5232 Villigen PSI
Switzerland

Head
Prof. Dr. Oliver Kröcher
Tel: +41 56 310 20 66
E-mail: oliver.kroecher@psi.ch

Secretariat
Gisela Herlein
Tel: +41 56 310 26 63
E-mail: gisela.herlein@psi.ch

Homepage ENE

Energy and Environment Research Division at PSI

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Archive 2006-2012. The Scientific Reports – containing accounts of research topics from all the different areas – provide an impression of the variety of subjects researched at PSI.


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