Dissociative Carbon Dioxide Adsorption and Morphological Changes on Cu(100) and Cu(111) at Ambient Pressures

摘要

Ambient-pressure X-ray photoelectron spec- troscopy (APXPS) and high-pressure scanning tunneling microscopy (HPSTM) were used to study the structure and chemistry of model Cu(100) and Cu(111) catalyst surfaces in the adsorption and dissociation of CO_2. It was found that the (100) face is more active in dissociating CO_2 than the (111) face. Atomic oxygen formed after the dissociation of CO_2 poisons the surface by blocking further adsorption of CO_2. This "self-poisoning" mechanism explains the need to mix CO into the industrial feed for methanol production from CO_v as it scavenges the chemisorbed O. The HPSTM images show that the (100) surface breaks up into nanoclusters in the presence of CO_2 at 20 Torr and above, producing active kink and step sites. If the surface is precovered with atomic oxygen, no such nanoclustering occurs.