Mukerji, Robin Jayanta; (2003) Studies of adsorption and reaction on the stepped Pt{211} surface. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The aim of the experiments presented in this thesis is to study the interaction of molecules on well defined stepped metal surfaces at various temperatures. To perform these experiments, an ultra high vacuum (UHV) system with an operating base pressure of below 2 X 10⁻¹⁰ mbar has been constructed. The UHV system is equipped with infrared optics to perform reflection absorption infrared spectroscopy (RAIRS), a quadrupole mass spectrometer for temperature programmed desorption (TPD), and electron optics for low energy electron diffraction (LEED) experiments. To allow experiments to be performed at various temperatures, a liquid helium cooled cryostat and a resistive heating mechanism were also incorporated into the system. This apparatus has been used to undertake an extensive study of the adsorption and reactions of various molecules on the Pt{211} surface. The initial system that was studied was the adsorption of CO on the Pt{211} surface over a range of temperatures. This adsorption system has been investigated previously and the results obtained here are in good agreement with earlier studies. However, the experiments described in this thesis also reveal additional experimental detail, not previously observed. Experiments were also performed to investigate NO adsorption on Pt{211} at 120 K and 300 K using both RAIRS and TPD . This adsorption system was found to be strongly temperature dependent and several different species were observed on the surface as a function of both temperature and exposure. A combination of experimental results and theoretical calculations, performed by Z-P Liu and P Hu of Queen's University Belfast, has allowed this complicated adsorption system to be understood for the first time. The final system that was studied was the co-adsorption of O and NO on the Pt{211} surface. The results show that only a moderate exposure of O has a large effect on the adsorption of NO on Pt{211}, inhibiting the formation of N2 and N2O as revealed in TPD experiments.

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