Oxygen vacancy distributions in a 5 nm CeO2 nanocube were determined using the Reverse Monte Carlo method. The oxygen vacancies tend to be located on the surface of the CeO2 nanocube, with far fewer in subsurface and internal regions.

Supported atomic dispersion metals are of great interest, and the interfacial effect between isolated metal atoms and supports is crucial in heterogeneous catalysis. Herein, the behavior of single-atom Cu catalysts dispersed on CeO2 (100), (110), and (111) surfaces has been studied by DFT + U calculations. The interactions between ceria crystal planes and isolated Cu atoms together with their corresponding catalytic activities for CO oxidation are investigated. The CeO2 (100) and (111) surfaces can stabilize active Cu+ species, while Cu exists as Cu2+ on the (110) surface. Cu+ is certified as the most active site for CO adsorption, which can promote the formation of the reaction intermediates and reduce reaction energy barriers. For the CeO2 (100) surface, the interaction between CO and Cu is weak and the CO adsorbate is more likely to activate the subsurface oxygen. The catalytic performance is closely related to the binding strength of CO to the active Cu single atoms on the different subsurfaces. These results bring a significant insight into the rational design of single metal atoms on ceria and other reducible oxides.

Cu clusters supported on CeO 2 have been reported as a promising and active catalyst for CO oxidation. However, the identification of interfacial interactions and active sites is still a great challenge. In this work, we demonstrated that interfacial chemistry can be understood and predicted by using a simple descriptor of adsorbate-surface interactions that uncovers structure-activity relationships. The catalytic activity of CeO 2 supported Cu clusters for CO oxidation was studied by density functional theory. The CuÀ Ce dual site mechanism enables the Cu/CeO 2 catalyst to have a much lower reaction energy barrier than the Mars-van Krevelen (M-vK) mechanism and the Cu-only mechanism. The reaction energy barriers of Cu/CeO 2-x with an oxygen vacancy on the CeO 2 surface were 0.10, 0.37 and 0.77 eV, respectively. The excellent performance of Cu/CeO 2 catalysts is related to the interfacial interaction between Cu and CeO 2 and their synergistic redox behaviors, and oxygen vacancies facilitate the generation and stabilization of active Cu + species through the interaction with Cu clusters. And we have identified the binding energy of O 2 * can describe the CO oxidation activity of Cu/CeO 2 . Our study provides insight into the nature of active sites for Cu/CeO 2 catalysts and guidance for high-performance.

Zero thermal expansion (ZTE) is an intriguing phenomenon by virtue of its peculiar lack of expansion and contraction with temperature. The achievement of ZTE in a metallic material is a desired but challenging task. Here we report the ZTE behavior of a single-phase metallic VB2 compound, stacking with the V and B atomic layers along the c direction (α V = 2.18 × 10–6 K–1, 5–150 K). Neutron powder diffraction demonstrates that the ZTE behavior is entangled in the direct blocking of the lattice expansion along all crystallographic directions with temperature. X-ray photoelectron spectroscopy and density functional theory calculations indicate that strong covalent binding adheres the nearest-neighbor B–B and V–B pairs, which is proposed to control the ZTE within both the basal plane and the c direction. An intimate correlation is revealed between the covalent binding and the lattice parameters. Our work indicates the opportunity to design metallic ZTE with strong chemical binding in the future.