Interaction of Atomic Hydrogen with the Cu₂O(100) and (111) Surfaces

Abstract

Reduction of Cu2O by hydrogen is a common preparation step for heterogeneous catalysts; however, a detailed understanding of the atomic reaction pathways is still lacking. Here, we investigate the interaction of atomic hydrogen with the Cu2O­(100):(3,0;1,1) and Cu2O­(111):(√3 × √3)R30° surfaces using scanning tunneling microscopy (STM), low-energy electron diffraction, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The experimental results are compared to density functional theory simulations. At 300 K, we identify the most favorable adsorption site on the Cu2O­(100) surface: hydrogen atoms bind to an oxygen site located at the base of the atomic rows intrinsic to the (3,0;1,1) surface. The resulting hydroxyl group subsequently migrates to a nearby Cu trimer site. TPD analysis identifies H2 as the principal desorption product. These observations imply that H2 is formed through a disproportionation reaction of surface hydroxyl groups. The interaction of H with the (111) surface is more complex, including coordination to both Cu+ and OCUS sites. STM and XPS analyses reveal the formation of metallic copper clusters on the Cu2O surfaces after cycles of hydrogen exposure and annealing. The interaction of the Cu clusters with the substrate is notably different for the two surface terminations studied: after annealing, the Cu clusters coalesce on the (100) termination, and the (3,0;1,1) reconstruction is partially recovered. Clusters formed on the (111) surface are less prone to coalescence, and the (√3 × √3)R30° reconstruction was not recovered by heat treatment, indicating a weaker Cu cluster to support interaction on the (100) surface.

Modifying the Lithiophilicity of Cu2O/Cu Collector by LiCuO to Restrain Lithium Dendrite Growth

“…Li 1s in Figure 2a. shows a signal peak at 54.8 eV, which is close to the previously reported signal peak at 54 eV of Li 2 O, and is presumably the Li + signal peak for LiCuO [31] . O 1s spectrum in Figure 2b.…”

“…shows a signal peak at 54.8 eV, which is close to the previously reported signal peak at 54 eV of Li 2 O, and is presumably the Li + signal peak for LiCuO. [31] O 1s spectrum in Figure 2b. shows three signal peaks at 531.5 eV, 530.1 eV and 529.4 eV, respec- ChemistrySelect tively.…”

Key activity descriptors of nickel-iron oxygen evolution electrocatalysts in the presence of alkali metal cations

“…This justifies that improved information of the reactivity of the Ni(Fe)OOH surface can be obtained by estimations of the local Lewis acidity and basicity of Ni, Fe and O lattice sites as a function of the intercalating cation. For this purpose, we have employed three local reactivity properties (estimated by DFT calculations) that have previously been shown to correlate with the acidity/basicity of surface sites [44][45][46] . We model undercoordinated "edge sites" since these have been established as the more reactive sites in the Ni-Fe catalyst (details on the model is provided in Supplementary Fig.…”

“…LiOH, NaOH, KOH, RbOH, CsOH). We further utilize DFT to explore the correlations between the OER activity and three reactivity properties: The local electron attachment energy E(r) 42 , the local average ionization energy Ī(r) 43 , and the electrostatic potential V(r), to predict how electrolyte cations influence the local Lewis acidity/basicity of the Ni-Fe(OOH) lattice sites [44][45][46] . In short, our data conclude that the modification of alkali metal cations on the OER activity can be explained as a response to a change in the electrolyte pH.…”

Stabilization of Cu2O through Site-Selective Formation of a Co1Cu Hybrid Single-Atom Catalyst

“…A 2 × 2 × 1 Monkhorst–Pack k -point mesh was used. The surface model used in the calculations was based on previous structures of the (√3 × √3)­R30° reconstruction of Cu 2 O­(111) that also has been verified by LEED and atomic resolution STM analysis. − The characteristic (√3 × √3)­R30° reconstruction of the Cu 2 O­(111) surface was generated by removing one-third of the unsaturated surface oxygen atoms, corresponding to one oxygen vacancy per surface unit cell. A second type of surface reconstruction with both 1/3 ML oxygen vacancies and 1 ML monolayer copper vacancies was also considered.…”