Adsorption and activation of molecular oxygen over atomic copper(I/II) site on ceria

Abstract

Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, we achieve selective oxygen (O 2) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3d orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a [Cu(I)O 2 ] 3− site selectively adsorbs molecular O 2 , forming a rarely reported electrophilic η 2-O 2 species at 298 K. Assisted by neighbouring Ce(III) cations, η 2-O 2 is finally reduced to two O 2− , that create two Cu-O-Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s −1 at 373 K and 0.01 bar P CO. The unique electronic structure of [Cu(I)O 2 ] 3− site suggests its potential in selective oxidation.

The Electrophilicity of Surface Carbon Species in the Redox Reactions of CuO‐CeO2 Catalysts

“…Fine powder of highly dispersed 20 wt % CuO clusters on CeO 2 with 71 m 2 g −1 specific surface area were prepared via flame spray pyrolysis [20b, 22] . The high‐resolution aberration‐corrected high angle annular dark field‐scanning transmission electron microscopy (HAADF‐STEM) images show crystalline CeO 2 particles with an average size of around 6 nm (Figure S1f,g).…”

“…We hypothesise that when the size of the Cu 2 O decreases, the curvature of the surface CuO layer increases and more Cu can be oxidised into Cu 2+ . An extreme case is the atomic Cu sites, which can be completely oxidised back to Cu 2+ even under He flow [22] …”

A computational investigation of the adsorption of small copper clusters on the CeO2(110) surface

“…The material has a high oxygen storage capacity (OSC) as it can easily shift between Ce 4+ and Ce 3+ , forming bulk and surface oxygen vacancies with consequent high reducibility 4 , which is further enhanced in well-defined ceria nanostructures, such as nanoparticles, nanorods, and nanocubes which expose (111), (110)/(100), and (100) surfaces, respectively [5][6][7] . Consequently, nanostructured ceria-based catalysts, such as CuO x /CeO 2 catalysts, are active in many reactions, for example, the water gas shift (WGS) reaction 8,9 and CO oxidation 10,11 .…”

“…Considering debatable active sites of promising CuO x /CeO 2 -nanorod catalysts in many reactions 8,10,11,17,18 , being it Cu species with different oxidation states, or the Cu-ceria interface, the understanding of atomic and electronic properties of small Cu clusters, a CuO x mono-and bilayer on CeO 2 (110), especially on a defective surface and at the copper-ceria interface, is thus of great interest and importance. However, there is a lack of comprehensive study of small Cu cluster morphologies and electronic interactions with CeO 2 (110) surface.…”

Photothermocatalytic Removal of CO and Formaldehyde with Excellent Water Vapor Stability over Dual‐Functional Copper Loading on TiO2 Synthesized via Flame Spray Pyrolysis

“…[11,15] Compared with the production of copper-based catalysts by traditional methods such as solÀgel, impregnation, and hydrothermal approaches, the flame spray pyrolysis (FSP) technology is a fast, economical, and scalable route to produce nanoparticles. [16] The FSP method can allow the one-step synthesis of nanocatalysts with controllable support and composition properties, due to a wide range of precursor types. In addition, the high purity and excellent dispersion of active sites are beneficial for higher reactivity of composite nanomaterials in catalytic oxidation.…”