6 Search Results

High-entropy alloy nanoparticles (HEA-NPs) are highly underutilized in heterogeneous catalysis due to the absence of a reliable, sustainable, and facile synthetic method. Herein, we report a facile synthesis of HEA nanocatalysts realized via an ultrasound-driven wet chemistry method promoted by alcoholic ionic liquids (AILs). Owing to the intrinsic reducing ability of the hydroxyl group, AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process. Under high-intensity ultrasound irradiation, Au³⁺, Pd²⁺, Pt²⁺, Rh³⁺, and Ru³⁺ ions were co-reduced and transformed into single-phase HEA (AuPdPtRhRu) nanocrystals without calcination. Characterization results revealmore » that the as-synthesized nanocrystals are composed of elements of Au, Pd, Pt, Rh, and Ru as expected. Compared to the monometallic counterparts such as Pd-NPs, the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity. Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.« less

Abstract High‐temperature pyrolysis of nitrogen (N)‐rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N‐carbon‐supported metal catalysts. Herein, covalent triazine framework (CTF) and CTF‐I (that is, CTF after charge modulation with iodomethane) are presented as sacrificial templates, for the synthesis of carbon‐supported Ru catalysts—Ru‐CTF‐900 and Ru‐CTF‐I‐900 respectively, following high‐temperature pyrolysis at 900 °C under N ₂ atmosphere. Predictably, the dispersed Ru on pristine CTF carrier suffered severe sintering of the Ru nanoparticles (NPs) during heat treatment at 900 °C. However, the Ru‐CTF‐I‐900 catalyst is composedmore » of ultra‐small Ru NPs and abundant Ru single atoms which may have resulted from much stronger RuN interactions. Through modification of the micro‐environment within the CTF architecture, Ru precursor interacted on charged‐modulated CTF framework shows electrostatic repulsion and steric hindrance, thus contributing toward the high density of single Ru atoms and even smaller Ru NPs after pyrolysis. A RuRu coordination number of only 1.3 is observed in the novel Ru‐CTF‐I‐900 catalyst, which exhibits significantly higher catalytic activity than Ru‐CTF‐900 for transfer hydrogenation of acetophenone.« less

Currently, a sonochemical-based technique for one-pot synthesis of entropy-stabilized perovskite oxide nanoparticle catalysts with high surface area is reported. The high-entropy perovskite oxides were synthesized as monodispersed, spherical nanoparticles with average crystallite size of ~5.9 nm. Taking advantage of the acoustic cavitation phenomenon in ultrasonication process, the nanoparticles of BaSr(ZrHfTi)O₃, BaSrBi(ZrHfTiFe)O₃ and Ru/BaSrBi(ZrHfTiFe)O₃ were crystallized as single-phase perovskite structures through ultrasonication exposure without calcination. Of utmost importance, the entropically-driven stability of Ru/BaSrBi(ZrHfTiFe)O₃ with excellent dispersion of Ru in the perovskite phase, bestowed the nanoparticles of Ru/BaSrBi(ZrHfTiFe)O₃ with good catalytic activity for CO oxidation.

Tuning the atomic interface configuration of noble metals (NMs) and transition-metal oxides is an effective straightforward yet challenging strategy to modulate the activity and stability of heterogeneous catalysts. Herein, Pd supported on mesoporous Fe₂O₃ with a high specific surface area was rationally designed and chosen to construct the Pd/iron oxide interface. As a versatile model, the physicochemical environments of Pd nanoparticles (NPs) could be precisely controlled by taming the reduction temperature. The experimental and density functional theory calculation results unveiled that the catalyst in the support–metal interface confinement (SMIC) state showed significantly enhanced catalytic activity and sintering resistance for COmore » oxidation. The constructed Fe sites at the interfaces between FeO_x overlayers and Pd NPs not only provided additional coordinative unsaturated ferrous sites for the adsorption and activation of O₂, thereby facilitating the activation efficiency of O₂, but also impressively changed the reaction pathway of CO oxidation. As a result, the catalyst followed the Pd/Fe dual-site mechanism instead of the classical Mars–van Krevelen mechanism. For the catalyst in the strong metal–support interaction (SMSI) state, its catalytic activity was seriously suppressed because of the excessive encapsulation of the active Pd sites by FeO_x overlayers. Thus, the present study therefore provides detailed insights into the SMIC and SMSI in ferric oxide-supported Pd catalysts, which could guide the preparation of highly efficient supported catalysts for practical applications.« less

Abstract A facile ultrasonication‐assisted wet chemistry method for preparing multicomponent alloy nanoparticles (NPs) including high‐entropy alloys (HEAs) is reported. PtAuPdRhRu alloy (HEA), quaternary PtAuPdRh alloy, and ternary PtAuPd alloy NPs are produced with ≈3 nm in diameter. Taking advantage of the acoustic cavitation phenomenon in ultrasonication process, noble metal precursors could be co‐reduced by chemical reductants and transform to alloy structures under operation at room conditions. The instantaneous massive energy (≈5000 °C, 2000 atm) occurring in momentary timespans (≤10 ⁻⁹ s) contributes to the formation of multimetallic mixed nanomaterials driven by entropy maximization. Owing to strong synergistic effects, the catalystsmore » with the HEA NPs supported on carbons exhibit prominent electrocatalytic activities for hydrogen evolution reaction.« less