Hydrogen Adsorption on Co Surfaces: A Density Functional Theory and Temperature Programmed Desorption Study

• DOI: 10.1021/cs2006586
• Publication Date: 2012-04-18T15:24:57Z
• Authors: Pieter van Helden; Jan-Albert van de...; Cornelis J. Wests...
• Keywords: Thermal desorption spectroscopy; Saturation (graph theory); Surface diffusion

Density functional theory (DFT) calculations and temperature programmed desorption (TPD) experiments were performed to study the adsorption of hydrogen on Co(111) Co(100) surfaces. On surface, is coverage dependent calculated energies are very similar those Co(0001) surface. The experimental saturation Co(111)/(0001) surface θmax ≈ 0.5 ML, although DFT predicts 1.0 ML. indicate that preadsorbed will kinetically impede process as approaches θ = giving rise this difference. Adsorption independent up 1.00 contrasting observations Ni(100) Hydrogen atoms have low barriers diffusion both A microkinetic analysis desorption, simulating expected TPD experiments, indicated two peaks expected, while only one peak expected. Low between 0.97 1.1 eV obtained from experiment a smooth single crystal Co(0001), in line with results. Defects play important role process. Further Co(211) Co(221) surfaces been model effects step defect sites, indicating steps defects expose broad range sites varying (mostly less favorable) energies. effect has studied by sputtering Co accelerate providing alternative, almost barrierless pathways, making it possible increase above 0.50 presence at high concentration give much lower activation energies, resulting features.