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Molecular beam studies of model NSR catalysts

Archard, Daniel 2008. Molecular beam studies of model NSR catalysts. PhD Thesis, Cardiff University.

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The adsorption and reaction of various simple molecules (O2, NO, CO and NO2) commonly associated with gasoline engine exhaust catalysis were investigated on a model catalytic system under ultra-high vacuum conditions using a variety of surface science techniques including molecular beam scattering and temperature programmed desorption. The model catalytic surfaces studied were clean Pt(111), K/Pt(111) and BaO/Pt(111) surfaces. The alkaline and alkaline earth metal surfaces were prepared by metal vapour deposition (in an oxygen background in the case of BaO) and annealing. Also investigated was the ability of each of the catalytic surfaces to oxidise NO and CO and to store and reduce NO2. It was found that the clean Pt(111) surface was effective at oxidising CO provided the oxygen was in an adsorbed atomic form. Pt(111) was also found to be effective in the reduction of NO2. NO and O2 were found to react in a gas phase reaction that made mixed molecular beam studies problematic however it was found when beaming NO with a background pressure of O2 that no Pt(111) catalysed surface reaction was observed. It was found that dosing K onto the Pt(111) surface increased the sticking coefficient of oxygen greatly and that more than a monolayer of K on the surface catalysed the reduction of NO to N2. Unlike the Pt(111) surface, K/Pt(111) was capable of storing NO2 without it being immediately reduced. Potassium peroxide however was found to prevent NO2 storage. In a similar fashion to K, NO2 was stored on BaO, being released as NO and O2 on heating. NO is partially reduced to N2O by the BaO surface at ambient temperature with increased temperature favouring complete reduction to N2.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303213236
Date of First Compliant Deposit: 30 March 2016
Last Modified: 09 Jan 2018 19:37

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