Adsorption and surface reactions of C2H2 and C2H4 on Co(0001)

Abstract

In this paper we have studied adsorption and surface reactions of acetylene and ethylene on Co(0001) in detail by temperature desorption spectrum (TDS), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). C2H4 adsorption at 130 and 300 K followed by subsequent heating mainly forms C2 clusters and graphitic carbon, respectively, while C2H4 decomposes at 400 and 500 K to form dominant graphitic carbon and carbon adatoms, respectively. C2H2 molecularly adsorbs at 130 K but exclusively dehydrogenates upon heating. The resulting C2H2(a) species at low coverages remains stable up to 400 K and then exclusively dehydrogenates into C2 clusters, while the resulting C2H2(a) species at high coverages remains stable up to 310 K and then majorly dehydrocyclizates into (C2H)n intermediates with ring structures at 340 K which further dehydrogenates into graphitic carbon, and minorly dehydrogenates into C2 clusters. Exposed at 370 K, C2H2 dehydrocyclizates into (C2H)n intermediates with ring structures. These temperature and coverage dependent surface reactions of C2H2 and C2H4 on Co(0001) greatly enrich our fundamental understanding of Co-catalyzed F-T synthesis reaction.