Activation of CO over Ultrathin Manganese Oxide Layers Grown on Au(111)

Abstract

Well-defined manganese oxide (MnO x ) overlayers with a controlled chemical state and coverage were deposited on Au(111), and CO activation at the model MnO x /Au­(111) surfaces was explored by combining treatments in high-pressure (up to 100 mbar) CO at elevated temperatures and in situ surface characterizations. We find that all MnO x nanostructures transformed into reduced MnO states (MnO1–y , 0 < y < 1) in the near-ambient pressure CO atmosphere, and dissociation of CO to carbon deposit occurs above 473 K. A volcano curve of the carbon deposit amount as a function of MnO coverage is clearly presented, indicating that MnO island edges are the active centers. Density functional theory calculations show that MnO/Au(111) interfaces provide edge Mn atoms coordinated with two oxygen atoms, where CO disproportionation occurs facilely through the CO dimer and further CCO* intermediates.

Brookite TiO2 Nanoparticles Decorated with Ag/MnOx Dual Cocatalysts for Remarkably Boosted Photocatalytic Performance of the CO2 Reduction Reaction

“…These results reveal that the mixed valence states of the Mn(II)/Mn(III) species (denoted as MnO x hereafter) exist in those Mncontaining composites. 48 Nevertheless, the BT-0.5Mn composite shows very weak Mn 2p signals, implying the very low actual loading amount. The possible reason may be that the photooxidation of Mn 2+ ions occurs with difficulty due to the lack of an electron-capturing reagent when only Mn 2+ ions are added to the BT suspension during the deposition process.…”

“…The high-resolution Mn 2p spectra (Figure d) of the 0.5Ag-BT-0.5Mn composite can be deconvoluted into two Gaussian components at 640.7/652.6 and 642.1/653.7 eV, which are ascribable to Mn­(II)­2p 3/2 /Mn­(II)­2p 3/2 and Mn­(III)­2p 1/2 /Mn­(III)­2p 1/2 , ,, respectively. These results reveal that the mixed valence states of the Mn­(II)/Mn­(III) species (denoted as MnO x hereafter) exist in those Mn-containing composites . Nevertheless, the BT-0.5Mn composite shows very weak Mn 2p signals, implying the very low actual loading amount.…”

Atomic‐Scale Observations of the Manganese Porphyrin/Au Catalyst Interface Under the Electrocatalytic Process Revealed with Electrochemical Scanning Tunneling Microscopy

“…This is supported by the emerged small O 1s peak at ≈529.2 eV, assigned to the oxidized manganese metal. [ 31 ] The origin of this cleavage may be due to Au oxidation on the anodic branch. However, given that cobalt (II) octaethylporphyrin decomposed into a thin film of CoO x on fluorine‐doped tin oxide during water oxidation, [ 30a ] it is more likely to be by another degradation factor, not Au substrate.…”

Predominance of Subsurface and Bulk Oxygen Vacancies in Reduced Manganese Oxide

“…Mn 3 O 4 films were grown on the Au(111) single crystal and Au foil, which were cleaned by cycles of Ar + sputtering (1.5 keV, 10 μA) and UHV annealing (800 K, 10 min). Mn atoms were evaporated by a Knudsen cell in 1 × 10 −6 mbar O 2 and with the substrate temperature at 300 K; then, the samples were annealed in 5 × 10 −6 mbar O 2 at 673 K. The deposition rate of Mn was calibrated by growing MnO on Pt(111) and then titrating the surface with 5 × 10 −7 mbar CO at 300 K. 24 After the preparation of Mn 3 O 4 films, we performed a temperature-programmed reaction for steps of 50 K, with each temperature in 100 mbar CO for 20 min; CO was pumped out for the following XPS tests. The variable-angle XPS was performed by tilting the sample with respect to the analyzer.…”