Re-visiting the O/Cu(111) system – when metastable surface oxides could become an issue!

Abstract

Surface oxidation processes are crucial for the functionality of Cu-based catalytic systems used for methanol synthesis, partial oxidation of methanol or the water-gas shift reaction. We assess the stability and population of the "8"-structure, a | 3 2 −1 2 | oxide phase, on the Cu(111) surface. This structure has been observed in x-ray photoelectron spectroscopy and low-energy electron diffraction experiments as a Cu(111) surface reconstruction that can be induced by a hyperthermal oxygen molecular beam. Using density-functional theory calculations in combination with ab initio atomistic thermodynamics and Boltzmann statistical mechanics, we find that the proposed oxide superstructure is indeed metastable and that the population of the "8"-structure is competitive with the known "29" and "44" oxide film structures on Cu(111). We show that the configuration of O and Cu atoms in the first and second layers of the "8"-structure closely resembles the arrangement of atoms in the first two layers of Cu 2 O(110), where the atoms in the "8"-structure are more constricted. Cu 2 O(110) has been suggested in the literature as the most active low index facet for reactions such as water splitting under light illumination. If the "8"-structure were to form during a catalytic process, it is therefore likely to be one of the reactive phases.Typeset by REVT E X 1

Solid-state chemistry of glassy antimony oxides

“…E tot is the total energy of the system, n Sb is the number of antimony atoms, E tot Sb is the total energy per atom of bulk Sb, n O is the number of oxygen ions in the system, Dm O is the chemical potential of oxygen referenced to the oxygen molecule, and E f,Sb is the formation energy of bulk antimony, which is zero here due to the choice of the reference state. The chemical potential of oxygen is calculated according to Richter et al, 29 with the experimental oxygen-binding energy of 5.22 eV being used to correct for the error in the PBE value.…”

Early and transient stages of Cu oxidation: Atomistic insights from theoretical simulations and in situ experiments

“…For Cu (111) surface oxidation, no ordered structures are observed at low oxygen exposure [79][80][81][82]. At higher exposure, hexagonal or quasihexagonal Cu-O super structures are observed on the Cu(111) surface [83][84][85][86][87][88], which are recognized as precursor and template for the further growth of Cu 2 O. Unlike (100) and (110) surfaces, the oxide domain on Cu(111) surface grows fast along the lateral direction and coalescence with each other, leads to the formation of 2D oxide film [44].…”

Atomic Structure and Work Function Modulations in Two-Dimensional Ultrathin CuI Films on Cu(111) from First-Principles Calculations

“…The theoretical approach, despite the fact that an electrical double layer is not explicitly considered, showed reasonably good agreements with relevant experiments. 31,38−40 We refer the readers to the references 23,25,40,41 for details of the theoretical approaches of (electrochemical) thermodynamics combined with ab initio DFT energetics. Now, we can compare the thermodynamic stability of ultrathin CuI layers on Cu(111) under the growth conditions to rationalize the experimentally observed global atomic geometry.…”

“…Near the experimental condition, the relative stability of interface structures is very competitive (see the inset of Figure 3a), which provides the possibility of the presence of metastable phases. 41 At the given condition, if the I H /Cu(111) structure is kinetically hindered, the thin CuI films such as H1L A , H2L A , and H3L A (or their structural relatives F1L A , B1L A , F2L A , B2L A , F3L A , and B3L A ) might be the dominant phases due to the small energy difference with respect to the ΔG ad of I H / Cu(111). Note that the averaged ΔG ad of 1L A , 2L A , and 3L A to that of I/Cu(111) are 0.009, 0.014, and 0.016 eV/Å 2 , respectively.…”