Structure Effects on Pyridine Hydrogenation over Pt(111) and Pt(100) Studied with Sum Frequency Generation Vibrational Spectroscopy

Catalytic reactions involving aromatic cyclic and heterocyclic molecules are important for the chemical industry for both fuel reforming and environmental concerns [ 1 ]. Hydrodenitrogenation chemistry is vitally important to the fuel reforming industry as nitrogen containing compounds inhibit the catalysts used for hydrodesulfurization through competitive adsorption [ 2 ] and act as a poison to acid catalysts [ 3 ]. Several recent works have focused on the understanding of the fundamental molecular level details of the adsorption and reaction of nitrogen containing aromatics on model platinum catalysts [ 4 – 7 ]. In general, molecular level studies of surface reactions are of paramount importance and is the subject of much current research [ 8 ]. Pyridine is a six-membered aromatic ring with one nitrogen heteroatom. The lone pair of electrons on the nitrogen atom is localized, meaning these electrons do not take part in the ring aromaticity. This means that pyridine is an electron donor, having the ability to donate electron density to a catalyst surface through either its π-aromatic orbitals or through σ-donation of the nitrogen lone pair to the surface.