Electronic structure studies of transition metal phosphides

The catalytic removal of sulfur from petroleum feedstocks, hydrodesulfurization (HDS), is an important industrial process. Traditionally, transition metal sulfides, especially MoS2 and its derivatives NiMoS and CoMoS, have been used as catalysts for this process. Recently, certain transition metal phosphides have been shown to exhibit high activity as HDS catalysts. These new potential HDS catalysts include WP, MoP, CoP, Ni2P, NiMoP, Co2P, and CoMoP. Very little is known about either the bulk or surface electronic structure of these phosphides.;Solid-state Fenske-Hall band structure calculations have been used to study the bulk electronic structure of all of the transition metal phosphides listed above and the electronic structure of selected surfaces of Ni 2P, NiMoP, and WP. The 0001 surfaces of both Ni2P and NiMoP and the 010 surface of WP were studied. The 0001 surfaces of Ni2P and NiMoP may expose either square pyramidal coordinated metal atoms (Ni for Ni2P and Mo for NiMoP) or tetrahedral metal atoms (Ni for both compounds) but not both. The 010 surface of WP is similar to the metal square pyramidal surface of Ni2P. The results discussed in chapters 2 and 3 present a detailed view of the bonding in these bulk solids and surfaces. The bonding picture is then correlated to HDS catalytic activity in order to determine what electronic features and surfaces may be important catalytically.