The Double-Edged Sword Effect of Water in the Low-Temperature CO Oxidation on Pt(111) Surface

Abstract

The positive and negative effects of water on low-temperature CO oxidation were comprehensively investigated on a Pt(111) surface by thermal desorption spectroscopy, X-ray photoelectron spectroscopy, and polarization-modulated infrared reflection absorption spectroscopy. At 110 K, the interaction between H2O and preadsorbed O2 forms the {O2(a)·(H2O)n} complex on the Pt(111) surface through hydrogen bonding. Upon heating the surface to 170 K, the O2 in the {O2(a)·(H2O)n} complex is subject to dissociation. On the O2-saturated Pt(111) surface (50 L O2/Pt(111)), part of the chemisorbed O2 on Pt(111) can be displaced by H2O and forms {O2(g)·(H2O)n} trapped by H2O molecules at high H2O coverage (>0.44 ML H2O). At this point, high H2O coverage also weakens the molecular oxygen dissociation. Regarding the CO oxidation, a new CO2 production channel by the interaction of CO with the {O2(a)·(H2O)n} complex at ∼153 K has been discovered by exposing H2O to the CO/O2/Pt(111) surface at 110 K, which dominates the low-t...