Date of Award
Master of Science in Chemical Sciences (MSCB)
The study of the surface of a meteoritic mineral, schreibersite (Fe,Ni)3P, was investigated to provide insight into the role of the mineral’s surface in aqueous-phase phosphorylation reactions. The optimization of a custom-designed ultrahigh vacuum (UHV) apparatus and Fe2NiP (schreibersite) surface was performed to permit surface science analysis. The bare surface was characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which showed some oxidation and segregation of phosphorous within the near-surface region. The interaction and/or reaction of water (H2O), methanol (CH3OH), formic acid (HCO2H) and other molecules with the schreibersite surface at varying surface temperatures was probed by reflection absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD). At surface temperatures of approximately 130 K, H2O interacts with Fe-P bridge sites while CH3OH does not appear to interact with surficial phosphorus. The interaction between HCO2H and surficial phosphorus is still under investigation. At 295 K, it is demonstrated that H2O dissociatively chemisorbs as OH- and lattice phosphorus undergoes oxidation. An increase in the surface temperature to about 500 K results in the recombinative desorption of OH- as H2O. Adsorption of other probe molecules such as H2 and CO were not detected in the RAIRS experiments, and low dosages of pyridine (C5H5N) on the Fe2NiP surface showed the presence of both Lewis and Brønsted acid sites.