Defect Engineering of High-Entropy Oxides for Superior Catalytic Oxidation Performance

Abstract

High-entropy oxides (HEOs) are crucial in various fields (power storage/conversion, electronic devices, and catalysis) owing to their adjustable structural characteristics, fabulous stability, and massive components. However, the current strategies for synthesizing HEOs suffer from low surface area and limited active sites. Herein, we present a salt-assisted strategy with remarkable universality for the preparation of HEOs with high surface area [e.g., HP-(FeCrCoNiCu) x O y : 59 m 2 /g, HP-(ZnMgNiCuCo) x O y : 49 m 2 /g, and HP-(CrMnFeNiZn) x O y : 11 m 2 /g], where HP means high porosity. Especially, HP-(FeCrCoNiCu) x O y with rich-oxygen vacancies promotes catalytic efficiency for hydrocarbon and alcohol oxidation owing to its hierarchical texture and massive oxygen vacancies. Furthermore, density functional theory is utilized to well illustrate the relationship of the structure and catalytic efficiency within the catalysts. This work offers realistic pathway for the large-scale application of HEOs in catalytic areas.

(CoFeMnCuNiCr)3O4 High-Entropy Oxide Nanoparticles Immobilized on Reduced Graphene Oxide as Heterogeneous Catalysts for Solvent-Free Aerobic Oxidation of Benzyl Alcohol

“…Recent studies demonstrated that these materials provide an outstanding platform for the engineering of novel catalysis and electrocatalysis with optimized performance. To name a few, Feng et al developed a Co 0.2 Ni 0.2 Cu 0.2 Mg 0.2 Zn 0.2 O high-entropy oxide (HEO) with a holey lamellar structure composed of nanoparticles, which exhibited superior catalytic activity for the solvent-free aerobic oxidation of benzyl alcohol with up to 98% conversion in 2 h. Zhang et al prepared a (FeCrCoNiCu) x O y HEO with high porosity through a salt-assisted technique. This HEO exhibited superior catalytic efficiency for the oxidation of benzyl alcohol (99.9% conversion with a selectivity of 83.5% for benzaldehyde at 383 K and 1 h), ethylbenzene, and C 3 H 6 owing to its massive oxygen vacancy concentration and hierarchical texture.…”

Engineering of Pore Design and Oxygen Vacancy on High-Entropy Oxides by a Microenvironment Tailoring Strategy

“…These obstacles result in the agglomeration of catalyst particles, reducing the specific surface area, lower porosity, and limited exposure of active sites, thereby diminishing catalytic performance. To deal with the above obstacles, our group utilized inorganic salts and metal–organic frameworks (MOFs) as templates and precursors to fabricate a series of HEOs with adjustable porosity and active sites. − However, the tedious procedure (removing templates and expensive precursors) significantly hinders its utilization on a large scale. Consequently, developing a low-temperature, rapid synthesis tactic for HEOs with abundant active sites (such as massive oxygen vacancies), rich porosity, and large surface area to boost the catalytic efficiency is imperative.…”

Solvent‐Free Oxidation of Benzyl Alcohol Using Modified Zeolitic Imidazolate Frameworks‐8 (ZIF‐8) Catalysts

“…Appropriate catalyst selection can significantly influence the success of attaining the desired product yield. Some heterogeneous catalysts that have been employed in the alcohol oxidation reaction include AuÀ Pd nanoparticles, [7] perovskite LaMO 3 (M = Cr, Mn, Co, Ni, and Fe), [8] high-entropy oxides (e. g. HP- (FeCrCoNiCu) x O y , HE-MOF, MW-HEO), [9][10][11] Ce Oxysulfate Clusters (MCe 70 , M = Ce, Cu, Ni, Co, and Fe), [12] as well as porous materials like zeolites, [13] nitrogen-doped carbon-encapsulated metallic Co nanoparticles, [14] and Metal-Organic Frameworks (MOFs). [15] Among heterogeneous catalysts, MOFs stand out as porous materials with promising potential across various organic reactions.…”