Abstract
Studies of the adsorption of O2 and CO on different faces of single crystal Ni held at T≂6 K are reported which provide direct evidence for a precursor adsorption preceding chemisorption. Values of the work function were obtained using the field-emission retarding potential method as Ni surfaces held at 6 K were exposed to O2 and CO and, subsequently, as the gas covered surfaces were annealed. Comparison with results for chemisorbed surfaces formed by gas exposure at 77 K indicates stabilized precursor adsorption phases at 6 K for O/Ni(111), O/Ni(100), and CO/Ni(111). Starting at temperatures on the order of 20 K, these convert at appreciable rates to the usual chemisorption phases. Analysis of the temperature and time dependence of the reaction rates indicates activation energies EA of approximately 13, 6, and 4 meV for O/Ni(111), O/Ni(100), and CO/Ni(111), respectively. Precursor adsorption was not observed for CO/Ni(100). Presumably the activation energy, if it exists, is too small for effective stabilization at 6 K.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.