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A simple angle-resolved thermal molecular beam reactor: applied to CO oxidation on Pt{110}

Bowker, Michael, Klink, Björn Udo, Lass, Kristian and Bennett, Roger A. 2020. A simple angle-resolved thermal molecular beam reactor: applied to CO oxidation on Pt{110}. Catalysts 10 (11) , 1229. 10.3390/catal10111229

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Abstract

We developed a simple form of thermal molecular beam catalytic reactor system which is capable of measuring sticking probabilities and reaction probabilities, together with angle-resolved scattering of molecules and products during catalytic reactions at the surface. This includes very fast determination of the angle dependence of the reaction product flux at steady-state. It was employed to determine the oxidation of CO on Pt{110}-(1 × 2), including individual molecular sticking and scattering. The initial sticking probability of oxygen on Pt{110} shows a small variation between 140 and 750 K surface temperature, from 0.45 to 0.28. The saturation uptake drops from 1.5 ± 0.2 ML at 140 K to 0.6 ML at 300 K and to 0.23 ± 0.02 ML at 750 K. The initial sticking probability of CO at 300 K is 0.80 and decreases to 0.62 at 470 K. Beyond that temperature, it descends steeply down to near zero at 570 K, due to the high desorption rate of CO at that temperature. Kisliuk precursor mobility parameters K were calculated from shape of the sticking curves. For 300 K, a value of 0.11 ± 0.01 was found, which increases to 0.76 ± 0.01 at 470 K, indicating a change from considerable mobility in the precursor state, to more limited mobility before desorption at high temperature. In temperature-programmed CO-O2 reaction experiments, CO2 production was observed to initiate in the temperature region 460–510 K. Using isothermal angle-resolved experiments, the CO2 flux was determined in the [11¯0] plane at temperatures of 470–620 K. Two sharp scattering lobes at positions of ±16° off the surface normal were found, with a high cosine power angle dependence, which were attributed to desorption from the {111}-like microfacets of the 1 × 2 reconstructed surface, with products evolving over a high barrier

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: MDPI
ISSN: 2073-4344
Funders: EPSRC
Date of First Compliant Deposit: 26 October 2020
Date of Acceptance: 21 October 2020
Last Modified: 27 Oct 2020 10:45
URI: http://orca.cf.ac.uk/id/eprint/135921

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