Catalysis Science & Technology最新文献

The development of non-precious metal overall water splitting electrocatalysts under high current density is of utmost importance in feasible water splitting technology. Herein, we present an ambient temperature sulfuration strategy through in situ construction of iron nickel sulfide nanosheets vertically on 3D microporous iron foam. The synthesis conditions are simple and conducive to large-scale production. The FeNiS/IF nanosheets exhibit outstanding performance towards the HER and OER at large current densities, even in the order of 1000 mA cm⁻². Density functional theory calculations show that FeNiS/IF as a bimetallic sulfide exhibits superior HER activity in alkaline media due to the optimization of ΔG_H* and a more favorable water adsorption process.

Here, we describe the direct exploitation of visible light energy by using a conjugated polymer network (CPN) that is susceptible to an in situ loading of Pd metal for photocatalytic Suzuki-type C–C cross-coupling reaction. The requisite products were quantitatively achieved (yield >90%), under photo-illumination using an environment-friendly solvent. Under normal solar light, similar catalytic activity was maintained using the same experimental conditions. To comprehend the function of every variable and reactive species involved in the reaction's path, in-depth mechanistic studies were carried out. It is further underlined that the CPN has greater catalytic efficiency based on its exceptional resistance to 50 substrates of varying functionality, for 5 consecutive catalyst recycling cycles as well as bulk-scale reactions and a turnover frequency value of up to 1840 h⁻¹ at a low catalyst dose of Pd (0.0125 mol%), while maintaining its catalytic efficacy. Its catalytic competence in terms of scope, scalability, environmental friendliness, and sustainability supports its proficiency.

Heretofore selective hydrodeoxygenation (HDO) of syringol remained limited and challenging due to the complicated structure of syringol compared to other lignin-derived model compounds such as guaiacol and phenol. Here, we report an efficient HDO of syringol to cyclohexanol (CYHAOL) over a reduced graphene oxide (rGO)-supported Co catalyst (Co/rGO) capable of heterolytic dissociation of H₂ molecules. A combination of characterization methods, including HAADF-STEM, XPS, XRD, etc., and experiments reveals that Co/rGO has a unique morphology composed of core–shell structured multivalent Co oxide nanoparticles (CoO_x) incorporating oxygen vacancies distributed on the graphene surface, and high-density single Co atoms embedded in the graphene matrix, both of which can afford the highly active H^{δ −} species for the HDO reaction. The morphologies of the supported Co species are highly dependent on the graphene textures. The Co/rGO catalyst without pre-reduction treatment demonstrated exceptional catalytic activity in the HDO of syringol with high selectivity to CYHAOL under mild conditions and good stability in the catalyst components. The metal-oxide-based Co/rGO catalyst does not require the pre-reduction treatment, simplifying the catalyst preparation process and eliminating the severe sintering of the metal species.

Herein, we designed a NIR (near-infrared)-responsive multifunctional nanoreactor that can be used for precise and immediate regulation of chemoenzymatic degradation of organophosphates (OPs). The thermophilic phosphotriesterases (PTEs) and gold nanoparticles (AuNPs) were encapsulated in the ZIF-8 structure yielding an Au/PTE/ZIF-8 nanocomposite, which can be modulated by NIR as a result of the photothermal effect of AuNPs. The Au/PTE/ZIF-8 nanoreactor demonstrated excellent performance in mediating cascade reactions from enzymatic hydrolysis of OPs (>90% conversion in 10 min) to the subsequent reduction of the resulting 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH₄ (>90% yield of 4-AP in 30 min). An immediate light-to-heat conversion when NIR was applied to Au/PTE/ZIF-8 at room temperature enables a 2-fold increase in the specific activity of phosphotriesterase from S. islandicus compared to thermo-heating at 70 °C. Based on the fact that there was a significant acceleration in 4-NP reduction by Au/PTE/ZIF-8, we proposed a plausible reaction mechanism (reaction pathway) suggesting that: 1) cooperative actions between Au, ZIF-8 and substrates take place by promoting polarization and cleavage of the B–H bond in NaBH₄ for releasing hydride facilitating electron and hydride transfer to 4-NP; and 2) stabilizing the formation of intermediates or the transition state by coordination with a ZIF-8 delocalized network and/or Au.

Elimination of volatile organic compounds (VOCs) via catalytic oxidation has been currently considered as one of the most efficient methods, where zeolite-based catalysts have emerged as highly promising materials in the realm of VOC oxidation due to their unique features including uniform and intricate channels, large surface areas, high adsorption capacities and high thermal and hydrothermal stabilities. This perspective offers a comprehensive analysis of the structure and composition of zeolites, serving as a foundation for understanding their varied performances in the catalytic oxidation of VOCs. Furthermore, it shows a range of challenges and opportunities aimed at enhancing the efficiency and reducing the cost of zeolite-based catalysts for their potential application in the catalytic oxidation of VOCs.

Exposure of acidic zeolite-based catalysts to water at high temperatures generally leads to deactivation due to dealumination. In Cu–CHA zeolite, which is a preferred catalyst for the selective catalytic reduction of NO by NH₃ (NH₃-SCR), the acidic protons in the zeolite are partially exchanged by Cu ions. The presence of Cu has been measured to reduce the rate of dealumination, thus stabilizing the catalyst. To understand the stabilizing effect of Cu, density functional theory calculations, ab initio thermodynamics and microkinetic modeling are used to compare the reaction mechanism for the dealumination of H–CHA to Cu–CHA. For H–CHA, we find that dealumination leads to the formation of mobile Al(OH)₃H₂O (extra-framework aluminum) species, whereas for Cu–CHA, formation of framework bound Cu–Al species is thermodynamically preferred over Al(OH)₃H₂O, which results in the increased stability of Cu–CHA. The formation of mobile Al(OH)₃H₂O in Cu–CHA is, moreover, associated with a high energy barrier. The phase diagrams show the formation of Al(OH)₃H₂O and Al₂O₃ from H–CHA and that high temperatures favor the formation of Al₂O₃. For Cu–CHA, high temperatures lead to the formation of CuO and Al₂O₃, which is favored over Al(OH)₃H₂O + CuO. The microkinetic model shows that the formation of Al(OH)₃H₂O in the presence of water starts at 380 K and 800 K in H–CHA and Cu–CHA, respectively. Additionally, the time evolution of the Al(OH)₃H₂O coverage at 923 K reveals that the process of dealumination is significantly faster for H–CHA as compared to Cu–CHA, which is in accordance with the measured increased stability.

In this study, three different metal oxides derived from metal–organic frameworks (MOFs), including CeO₂, ZrO₂, and Fe₂O₃ were used as porous supports for loading Pt nanoparticles, and the supported catalysts (viz., Pt/CeO₂, Pt/ZrO₂, and Pt/Fe₂O₃) were evaluated for the catalytic deoxygenation of stearic acid to produce olefins by analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Interestingly, Pt/CeO₂ and Pt/Fe₂O₃ catalysts demonstrated high selectivity for olefins or aromatics, respectively, with alkanes as minor products, while the Pt/ZrO₂ catalyst demonstrated the lowest deoxygenation efficiency. Among them, the Pt/CeO₂ catalyst demonstrated the highest deoxygenation efficiency due to its highest oxygen vacancy density and the largest specific surface area (53 m² g⁻¹). It also demonstrated the highest selectivity for olefins (41%) due to the in situ partial formation of the bimetallic PtCe phase during the catalytic reaction at high temperature, which facilitates the decarbonylation pathway and leads to the formation of olefins as the main product. In addition, experimental optimizations of the reaction parameters were conducted on the designed Pt/CeO₂ catalyst to further enhance olefin selectivity. Importantly, the Pt/CeO₂ catalyst also maintained high olefin selectivity and stearic acid conversion even after six consecutive cycles. Therefore, this work has provided an alternative route to produce olefins via the decarbonylation of stearic acid over a supported Pt/CeO₂ catalyst.

A novel composite material composed of WO₃, Ti₃C₂T_x MXene, and Au for the photocatalytic formation of hydrogen peroxide (H₂O₂) is introduced here. Through optimization, the ideal MXene and Au concentrations were determined to be both 0.5%. And after loading Au and MXene the amount of H₂O₂ generated increases to 7.52 mg L⁻¹ at pH 3, which is a remarkable 21.5-fold increase. Quenching experiments unequivocally revealed identified ·O₂⁻ as the predominant intermediate product, indicating a two-stage, single-electron indirect mechanism. Enhanced effectiveness for H₂O₂ synthesis is ascribed to the synergistic impact of Ti₃C₂T_x MXene and gold, enhancing charge transfer efficiency while impeding the recombination of these electron–hole pairs.

The impact derived from incorporating water into CH₄/CO₂ biogas stream for the generation of syngas was investigated over the Rh/MgAl₂O₄ catalyst using operando steady-state and transient DRIFT spectroscopy coupled with MS. The incorporation of steam resulted in improved CH₄ conversion rates and attained syngas streams with higher H₂/CO ratios. It was demonstrated that in the presence of steam, the generation of CH_xO species through the reaction of CO* with active *OH species is favored at the metal support surface. Besides, the enhanced resistance delivered by water molecules towards deactivating the coking phenomena was associated with easier carbonaceous decomposition and the exposition of the very active Rh (100) surfaces for methane decomposition. The Rh/MgAl₂O₄ catalyst was demonstrated to be an effective catalyst for the production of H₂-rich syngas streams. More importantly, the insights reported herein provide new evidences regarding the impact of steam on biogas reforming reactions.

Chemoselective α-C–H functionalization of β-naphthol is achieved with inexpensive and readily available alcohols using a well-defined, air-stable, and easy-to-prepare Ru(ii)-catalyst (1a) bearing a redox-active tridentate pincer (L1a). Only 1.0 mol% of 1a showed promising catalytic efficiency, producing various α-alkylated β-naphthols in moderate to good isolated yields starting from different aromatic, hetero-aromatic, and aliphatic alcohols, including methanol, ethanol, and other long-chain alcohols. 1a also efficiently catalyzes the α-C–H alkylation of β-naphthols using aromatic diols as the di-alkylating agent. 1a also exhibited promising results during the large-scale synthesis of α-alkylated β-naphthols. Mechanistic investigation revealed that the 1a-catalyzed α-C–H functionalization of β-naphthol proceeds via a borrowing hydrogen path where hydrogen is transferred from alcohol to the azo-chromophore of the tridentate pincer via a transient ruthenium hydride intermediate, which was transferred in the later stage to the in situ formed alkylidenenaphthalen-2(1H)-one intermediate, producing α-alkylated β-naphthols as the final product.