Sum Frequency Generation and Polarization–Modulation Infrared Reflection Absorption Spectroscopy of Functioning Model Catalysts from Ultrahigh Vacuum to Ambient Pressure

摘要: Abstract It has long been debated whether the results of classical surface science investigations carried out under ultrahigh vacuum (UHV) can be truly transferred to heterogeneous catalysis, which is normally at ambient or even higher pressures. In an effort answer this question, several surface-sensitive methods have developed that operate in a pressure range from UHV 1 bar. By application characterization single-crystal surfaces as well supported nanoparticles while they are functioning catalysts, and materials gaps between catalysis simultaneously bridged. Vibrational spectroscopy techniques, like infrared-visible (IR-vis) sum frequency generation (SFG), polarization–modulation IR reflection absorption (PM-IRAS) applied characterize adsorption, coadsorption, reaction small molecules on transition metal (palladium, platinum, rhodium, gold, ruthenium, etc.) pressures ranging The goal these mbar elucidate elementary steps catalytic reactions. considered here include CO adsorption dissociation, oxidation hydrogenation, ethene methanol decomposition partial taking place low-index surfaces, defect-rich (stepped ion-bombarded) oxide-supported nanoparticles. When available, complementary structural information determined by high-pressure scanning tunneling microscopy (HP-STM) compositional analysis photoelectron (HP-XPS) included. implications high mechanisms reactions discussed, potential future research directions suggested.