Design parameters for measurements of local catalytic activity on surfaces

Martin Johansson, Tue Johannessen, Jan Hoffmann Jørgensen, Ib Chorkendorff

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Computational fluid dynamics in combination with experiments is used to characterize a gas sampling device for measurements of the local catalytic activity on surfaces. The device basically consists of a quartz capillary mounted concentrically inside an aluminum tube. Reactant gas is blown toward the catalytic surface through the annulus between the tubes, and the gas is sampled close to the surface by the capillary. The influence of various design parameters on the lateral resolution and sensitivity of the measurements is investigated. It is found that the cuter diameter of the annulus sets the upper limit for the lateral resolution of the measurement, and that a flow rate of the order of 240 (ml/min)(n) is sufficient to achieve this resolution. The sensitivity is reasonable also with high flow rates, due to the presence of a pocket of stagnant gas under the tip of the capillary. Furthermore, the limits of the range in reaction rate, which can be Studied are estimated. (c) 2005 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalApplied Surface Science
Issue number10
Pages (from-to)3673-3685
Publication statusPublished - 15 Mar 2006


  • heterogeneous catalysis
  • local gas sampling
  • local reaction rate


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