Defect Engineering of Ceria Nanocrystals for Enhanced Catalysis via a High-Entropy Oxide Strategy

Abstract

Introducing transition-metal components to ceria (CeO 2 ) is important to tailor the surface redox properties for a broad scope of applications. The emergence of high-entropy oxides (HEOs) has brought transformative opportunities for oxygen defect engineering in ceria yet has been hindered by the difficulty in controllably introducing transition metals to the bulk lattice of ceria. Here, we report the fabrication of ceria-based nanocrystals with surface-confined atomic HEO layers for enhanced catalysis. The increased covalency of the transition-metal−oxygen bonds at the HEO− CeO 2 interface promotes the formation of surface oxygen vacancies, enabling efficient oxygen activation and replenishment for enhanced CO oxidation capabilities. Understanding the structural heterogeneity involving bulk and surface oxygen defects in nanostructured HEOs provides useful insights into rational design of atomically precise metal oxides, whose increased compositional and structural complexities give rise to expanded functionalities.

Structural Defects in Phase‐Regulated High‐Entropy Oxides toward Superior Microwave Absorption Properties

“…Rost et al [5] reported the first HE oxide with a rock salt phase in 2015, which has led to the research of various crystalline phases (such as spinel [8] and perovskite [9] ). Several experiment studies have demonstrated that single-phase HE ceramics, with their excellent entropy-stabilized and semiconductor properties, can be effectively applied in the fields of energy storage, [10] catalysis, [11] thermoelectricity, [12] and wear-resistant coatings. [12] However, the poor interfacial polarization of single-phase ceramics significantly affects the wave-absorbing capability of HE oxides.…”

Modulating Electronic Structure to Improve the Solar to Hydrogen Efficiency of Cobalt Nitride with Lattice Doping

“…After transition metal doping, the single Co–N peak splits to multiple deconvoluted peaks for M-Co 3.75 N 0.14 samples which correspond to different M–N bond lengths. This indicates the increased disordering structure in the M-Co 3.75 N 0.14 lattice . The nearest Co–Co peak is located at ∼2.54 Å, while this Co–Co bond becomes shorter after transition metal doping.…”

“…This indicates the increased disordering structure in the M-Co 3.75 N 0.14 lattice. 27 The nearest Co−Co peak is located at ∼2.54 Å, while this Co−Co bond becomes shorter after transition metal doping. Based on the above structural analysis, it can be concluded that the doping of transition metal will cause structural defects and lattice distortion in M-Co 3.75 N 0.14 , which are beneficial for the formation of nitrogen vacancies (as active sites).…”

“…Pair distribution function (PDF) analysis further confirms this change of surface properties for M-Co 3.75 N 0.14 samples. Different from Rietveld refinements that focus on Bragg diffraction peaks, PDF analysis combined with Bragg scattering with diffuse scattering information is useful to analyze the short-range structures of nanomaterials. , As shown in Figure f, the first negative g ( r ) peak at ∼1 Å can be attributed to the surface-adsorbed O–H bonds, due to the negative coherent nuclear scattering length of hydrogen. The peak at ∼1.9 Å is assigned to the metal–nitrogen (M–N) bond .…”

Nonclassical Strong Metal–Support Interactions for Enhanced Catalysis

“…The lower onset temperature shows a lower energy barrier for lattice oxygen activation, which is ascribed to the high-entropy effect. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”