Adsorption of Water on TiC(100):  Evidence for Complex Reaction and Desorption Pathways

The interaction of water with the nonpolar TiC(100) face has been probed as a function of surface temperature over the range 98−773 K. Temperature-programmed desorption (TPD) has been used to monitor the desorption products as a function of coverage while high-resolution electron energy loss spectroscopy (HREELS) has been used to probe the nature of adsorbed species as a function of surface temperature. Together, these molecularly specific probes reveal the presence of both molecularly and dissociatively adsorbed water in the monolayer regime at cryogenic temperatures. Furthermore, both Ti and C surface atoms participate in the dissociation of water and lead to the production of a complex array of surface species. With increasing surface temperature, the desorption species D2O, CO, CO2, and D2 are observed over a broad temperature range. The desorption of CO and CO2 demonstrates the consumption of carbon from the TiC surface while the desorption of D2 is thought to be related to presence of carbon vacancies known to exist within this and other metal carbides.