%0 Journal Article
%T Iron Carbidization on Thin-Film Silica and Silicon: A Near-Ambient-Pressure X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy Study
%J -
%D 2018
%R https://doi.org/10.1021/acscatal.8b02076
%X Model catalysts consisting of iron particles with similar size deposited on thin-film silica (Fe/SiO2) and on silicon (Fe/Si) were used to study iron carbidization in a CO atmosphere using in situ near-ambient-pressure X-ray photoelectron spectroscopy. Significant differences were observed for CO adsorption, CO dissociation, and iron carbidization when the support was changed from thin-film silica to silicon. Stronger adsorption of CO on Fe/Si than that on Fe/SiO2 was evident from the higher CO equilibrium coverage found at a given temperature in the presence of 1 mbar of CO gas. On thin-film silica, iron starts to carbidize at 150 ˇăC, while the onset of carbidization is at 100 ˇăC on the silicon support. The main reason for the different onset temperature for carbidization is the efficiency of removal of oxygen species after CO dissociation. On thin-film silica, oxygen species formed by CO dissociation block the iron surface until ˇ«150 ˇăC, when CO2 formation removes surface oxygen. Instead, on the silicon support, oxygen species readily spill over to the silicon. As a consequence, oxygen removal is not rate-limiting anymore and carbidization of iron can proceed at a lower temperature
%U https://pubs.acs.org/doi/10.1021/acscatal.8b02076