Thermodynamics of carbon coadsorbed with sulfur on Ni(100)

摘要: The thermodynamics of the segregation dissolved carbon to a Ni(100) surface containing adsorbed sulfur has been studied by stimulated desorption using low-current pulsed Ar+ beam at 2 keV, followed laser ionization 193 nm desorbed neutral species and reflecting time-of-flight mass spectrometry resulting C+ photo ions. Equilibrium surface-carbon coverages were measured for fractional 0, 0.1, 0.16, 0.26 monolayer over temperature range 700 1100 K. Absolute calibrated Auger electron spectroscopy saturated, ordered overlayer structures. Identical carbon-segregation obtained both increasing decreasing profiles indicated that represented equilibrium values. For <0.15 with respect number nickel atoms, heat formation on was -28 ±7 kJ/mol; Langmuir-McLean model used describe segregation. increases coverage. Coadsorbed does not affect ⩽0.16 monolayer. coverage monolayer, -7 ± kJ/ mol. reduces maximum segregated from 0.5 no coadsorbed 0.24 influence during methanation is discussed.