Ab initio study of the H-2-H2S/MoS2 gas-solid interface: The nature of thecatalytically active sites

Despite the intense research efforts directed toward understanding the micr oscopic mechanism of hydrodesulfurization reactions on transition-metal-sul fide catalysts, the nature of active sites remains an open question. Indust rial catalysts are mostly based on supported highly dispersed MoS2, There i s a general agreement that the active centers are coordinatively unsaturate d sites at the edge surfaces oriented parallel to the hexagonal axis of thi s layered sulfide, but the precise local structure is still unknown. In the present ab initio study, we show that the nature and the concentration of the active sites as well as the shape of the MoS2 crystallite can vary with the chemical potentials in the reactive atmosphere above the surface. We a lso report a precise investigation of the surface structure, chemical compo sition, and electronic properties of the MoS2 edge surface under working co nditions. (C) 2000 Academic Press.