Hydrogen Spillover Enhanced Hydroxyl Formation and Catalytic Activity Toward CO Oxidation at the Metal/Oxide Interface

Abstract

H2-promoted catalytic activity of oxide-supported metal catalysts in low-temperature CO oxidation is of great interest but its origin remains unknown. Employing an FeO(111)/Pt(111) inverse model catalyst, we herewith report direct experimental evidence for the spillover of H(a) adatoms on the Pt surface formed by H2 dissociation to the Pt-FeO interface to form hydroxyl groups that facilely oxidize CO(a) on the neighboring Pt surface to produce CO2. Hydroxyl groups and coadsorbed water play a crucial role in the occurrence of hydrogen spillover. These results unambiguously identify the occurrence of hydrogen spillover from the metal surface to the noble metal/metal oxide interface and the resultant enhanced catalytic activity of the metal/oxide interface in low-temperature CO oxidation, which provides a molecular-level understanding of both H2-promoted catalytic activity of metal/oxide ensembles in low-temperature CO oxidation and hydrogen spillover.

Proton-Transfer-Connected Elementary Surface Reaction Network for Low-Temperature CO Oxidation Catalyzed by Metal-Oxide Nanocatalysts

“…This indicates that the adsorption and decomposition of O 2 at the FeO−Pt interface should be blocked by the presence of 18 OD and that the 16 O species should form only on the Pt surface. Therefore, under our experimental conditions, the 18 O species is exclusively at the FeO−Pt interface while the 16 O species is exclusively on the Pt surface. A C 16 O 18 O desorption peak (δ′) was also observed at 288 K and could be inferred by the location of 18 O species to result from the CO Pt + O Pt + 18 Third, the proton transfer processes between the Pt surface and FeO−Pt interface bridge various surface reactions to constitute a surface reaction network to produce CO 2 .…”

“…All experiments were performed in a stainless-steel UHV system equipped with a polarization-modulated infrared reflection−absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), differentially pumped quadrupole mass spectrometer (QMS), and e-beam evaporator. 16 O 2 (>99.999%) were purchased from Nanjing ShangYuan Industry Factory and used as received. 18 O 2 ( 18 O > 97%) was purchased from Sigma-Aldrich.…”

Reactivity of hydrogen species on oxide surfaces

“…Co-adsorbed H species on Pt of FeO 1-x /Pt(111) inverse model catalysts was also observed to migrate to the FeO 1-x -Pt interface to increase the surface lattice-OH coverage, leading to enhanced CO+OH interfacial reaction probability and subsequent CO 2 production [39]. The suppression of surface lattice-OH groups-to-water reaction on CeO 2 surfaces was observed to open up the reaction pathway of surface lattice-OH groups with co-adsorbed C 2 H 2 species to produce C 2 H 4 [40,41].…”

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

“…Recently, significant progress in the CO oxidation catalyzed by metal-oxide nanocatalysts at or below room temperature was made. , In the low-temperature CO oxidation, previous results found that catalytic performances depend sensitively on the presence of H 2 O in the reaction stream; − thus this brought strong debates on the active structure and reaction mechanism. For example, the Pt–Fe­(OH) x interface and the Pt–FeO interface ,− were proposed, respectively, as the active structures to catalyze low-temperature CO oxidation.…”