Spectroscopy under the surface: In-Situ ATR-IR Studies of Heterogeneous Catalysis in Water.

The work described in this thesis demonstrates the application of ATR-IR infrared spectroscopy to study adsorption and catalytic reactions on metal surfaces during heterogeneous catalytic reactions in aqueous phase. By coating an Internal Reflection Element (IRE) with a stable, thin (in the order of a few microns) catalyst layer, adsorption and reaction at the solid-aqueous interface was studied successfully. Properties of the technique and the influence of water on the supported metal catalysts were demonstrated using two reactions (i) CO oxidation and (ii) nitrite hydrogenation. CO is a widely applied molecule to characterise supported noble metal catalysts andCO oxidation is a very simple reaction. Therefore CO adsorption and oxidation wasused to demonstrate the technique and to give insight in the behaviour of supportedcatalysts in water. Denitrification, nitrite hydrogenation, is becoming more importantdue to the high nitrite and nitrate levels found in ground-water in Europe and theincreasingly strict regulations for drinking water quality. The hydrogenation can beperformed over single noble metal catalysts such as platinum and palladiumcatalysts. The heterogeneous hydrogenation of nitrite was investigated by ATR-IR, inorder to resolve the hydrogenation mechanism.