Elementary Surface Reactions on Co(0001) under Fischer–Tropsch Synthesis Conditions

A fundamental understanding of Fischer–Tropsch synthesis (FTS) is challenging but important for catalyst design. We herein report high-resolution photoemission spectroscopic characterizations of a Co(0001) surface pretreated with syngas at different conditions without exposure to air. Elementary surface reactions were observed to sensitively depend on reaction pressures and temperatures. Both direct CO dissociation and H2-assisted CO activation for CO activation occur facilely at 300 K, while the removal of the resulting oxygen adatoms needs high temperatures. Under a typical FTS reaction condition (4 bar and 490 K), the Co(0001) surface is metallic, and direct CO dissociation is the dominant mechanism for CO activation to form irreversibly adsorbed surface intermediates including carbidic carbon, hydrocarbon fragments, atomic oxygen, and hydroxyl groups. These results significantly advance the fundamental understanding of the cobalt-catalyzed FTS process.