De moleculaire polder

Populariserende publicati

Dynamical probes of chemical interactions at interfaces

We report on the application of two experimental techniques developed in the field of atomic and molecular physics to investigate the dynamics of catalytic processes on a molecular scale in (model) cata!ysts. With these techniques, time-resolved pump-probe laser spectroscopy and molecular beam scattering, better insights into the fundamental processes relevant to catalysis can be obtained. With the first technique, time-resolved (picosecond) non-linear infared spectroscopy, zeolite catalysts and zeolite-adsorbate interactions are investigated. Microscopic structural information on the bare catalyst, as well as insights into the dynamics of interaction processes between catalyst and reactant (viz. zeolite and adsorbate) on a molecular scale are obtained. With the second technique, a molecular beam experiment, we obtain dynamical information on the interaction between catalytic metal surfaces and molecules; transient surface species and steric effects are observed

Obituary for Sydney Davison: the founder of progress in surface science

Catalysis and Surface Chemistr

Infrared picosecond transient hole-burning studies of the effects of hydrogen bonds on the vibrational line shape

With infrared transient hole-burning spectroscopy we have investigated the influence of OD ... X hydrogen bonds on the vibrational line shape of O-D stretch vibrations in acid zeolites. The effect of hydrogen bonding on the line shape depends critically on the type of hydrogen bond. For hydrogen bonding in a rigid structure, the hydrogen bond determines the inhomogeneous linewidth, but the homogeneous linewidth is determined by coupling to a similar to 200 cm(-1) lattice mode as concluded from the temperature dependence of the dephasing rate. When the hydrogen bond is formed with an adsorbing molecule, the coupling between the high-frequency O-D stretch vibration and the low-frequency OD ... X hydrogen-bond stretching mode does determine the homogeneous linewidth. The difference between the two systems can be explained by the different hydrogen-bond potentials. Variation of the adsorbate provides a means of obtaining conclusive information on the coupling mechanism between the high-frequency O-D stretching mode and the low-frequency OD ... X hydrogen-bond stretching mode. (C) 1996 American Institute of Physic

Conversion of CO2 by non- thermal inductively-coupled plasma catalysis

CO2 decomposition is a very strongly endothermic reaction where very high temperatures are required to thermally dissociate CO2. Radio frequency inductively-coupled plasma enables to selectively activate and dissociate CO2 at room temperature. Tuning the flow rate and the frequency of the radio frequency inductively-coupled plasma gives high yields of CO under mild conditions. Finally the discovery of a plasma catalytic effect has been demonstrated for CO2 dissociation that shows a significant increase of the CO yield by metallic meshes. The metallic meshes become catalysts under exposure to plasma to activate the recombination reaction of atomic O to yield O2, thereby reducing the reaction to convert CO back to CO2. Inductively-coupled hybrid plasma catalysis allows access to study and to utilize high CO2 conversion in a non-thermal plasma regime. This advance offers opportunities to investigate the possibility to use radio frequency inductively-coupled plasma to store superfluous renewable electricity into high-valuable CO in time where the price of renewable electricity is plunging.</p