Catalysis Letters最新文献

MgCoFe layered double oxides (MgCoFe-LDO) were fabricated to activate peroxymonosulfate (PMS) for degradation of sulfamethoxazole (SMX), and the highly efficient degradation of SMX revealed an excellent catalytic activity of Mg₂Co₁Fe₁-LDO for PMS under different pH values and water matrix. Scanning electron microscope analysis indicated the catalyst has a typical “flower-like” structure, and the X-ray powder diffraction analyses proved that the main crystal phase of Mg₂Co₁Fe₁-LDO is CoFe₂O₄ and Mg_1−xFe_xO, which is responsible for the good catalytic activity of Mg₂Co₁Fe₁-LDO. The radical scavenging experiments confirmed that ¹O₂, ({text{SO}}_{4}^{cdot - }), OH and ({text{O}}_{2}^{cdot - }) were involved in the degradation of SMX, but ¹O₂ and ({text{SO}}_{4}^{cdot - }) played the dominant roles. According to the X-ray photoelectron spectroscopy (XPS) of Mg₂Co₁Fe₁-LDO catalyst, it was referred that the species including CoOH⁺, CoO⁺, Fe³⁺, FeOH²⁺, Fe²⁺, etc. involve in the activation process of PMS. Moreover, the possible degradation pathways of SMX were proposed according to the detected intermediates including N-hydroxy sulfamethoxazole, 3-amino-5-methylisoxazole from LC–MS analysis, and the toxicity analysis via Toxicity Estimation Software Tool software shows that most of the degradation products of SMX have lower toxicity than SMX.

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The heterojunction construction through the effective combination of two metal sulfides can significantly improve the photocatalytic performance in the visible light region. In order to improve the photocatalytic efficiency of molybdenum disulfide (MoS₂), we synthesized a series of CdS/MoS₂ (CM) composites using a simple hydrothermal method. Their photocatalytic activities were evaluated by the photocatalytic hydrogen production. The results showed that the photocatalytic hydrogen production rate of CM composites was significantly enhanced after visible light irradiation, which was attributed to the improvement of visible light absorption capacity, efficient separation of photogenerated carriers, strong photocurrent response, and fast charge mobility. What’s more, sample CM-3 exhibited the highest photocatalytic hydrogen production efficiency of 2809.4 μmol g⁻¹ h⁻¹ compared to pure MoS₂ (0 μmol g⁻¹ h⁻¹) and CdS (81.5 μmol g⁻¹ h⁻¹). Therefore, the successful construction of heterojunction can accumulate much more photogenerated electrons for MoS₂, which is favorable to enhance its photocatalytic hydrogen production. This study provides strong evidence that heterojunction construction can obviously improve the photocatalytic activity.

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Photocatalytic H2 production of CM-3 composite. MoS2 constructed heterojunction with CdS can effectively improve the photocatalytic activity. The photocatalytic H2 production rate of CdS/MoS2 composite can reach 2809.4 μmol g-1 h-1

The Pt-based catalysts are quite promising for ethylene glycol oxidation reaction (EGOR) due to their superior catalytic activity and their high cost, low reserves and poor stability of precious metals greatly limit the further large-scale application. Developing low-Pt and high-performance anode electrocatalysts is urgent to direct ethylene glycol fuel cells. At present, a high-entropy alloy (HEA) of PtPdNiCoBi/C has been developed for EGOR, and its catalytic performance has been verified by electrochemical and physical methods. Notably, the EGOR peak current density on PtPdNiCoBi/C (0.782 A mg⁻¹_PtPd) reaches 3.54 times of Pt/C (0.221 A mg⁻¹_Pt), and the residual current on PtPdNiCoBi/C (0.092 A mg⁻¹_PtPd) is superior to that of Pt/C (0.076 A mg⁻¹_Pt) after 3000 s. Moreover, the current density retention (84.0%) of it after 500 cycles, is also superior to that of the Pt/C (78.8%). This work would support the future practical use of HEA catalyst for fuel cells.

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The elimination of lactones is a crucial method for preparing corresponding cycloalkane derivatives, but the commonly used catalyst NaI is unstable and non-recyclable. In this work, reusable MgI₂@SiO₂ was prepared for heterogeneous catalytic lactone elimination. Cyclopropyl methyl ketone was synthesized from 2-acetyl-γ-butyrolactone using MgI₂@SiO₂ as a catalyst at 180 °C and 1 atm. The yield and selectivity were both over 99%. The activity of MgI₂@SiO₂ was estimated to be 11 times that of NaI. The high activity of MgI₂@SiO₂ is attributed to the Lewis hard acidity of Mg²⁺ and the soft basicity of I⁻. The high selectivity of Cyclopropyl methyl ketone comes from the faster reaction rate, and its good stability is due to the strong interactions between Mg²⁺ and I⁻ with the carrier. This work provides a feasible scheme for the efficient and low-cost elimination synthesis of corresponding cycloalkanes from lactones.

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Industrial Bi-Mo-Fe-Co composites catalysts for propylene oxidation, are consist of two main components: Bi-Mo oxidate for propylene activation and Fe-Co oxidate for oxygen activation. But there are three different Bi-Mo crystalline phases, i.e., α-Bi₂Mo₃O₁₂, β-Bi₂Mo₂O₉, γ-Bi₂MoO₆, their role in catalytic oxidation process is unclear. In this paper, above three kinds of Bi-Mo phase are prepared at first, then coupled them respectively with Fe-Co oxidates by ball milling method to manufacture Cat-α, Cat-β, and Cat-γ. It is showed that their catalytic performance for propylene oxidation to acrolein, has the order of Cat-α > Cat-β > Cat-γ, and the Cat-α exhibit the best propylene conversion (90.1%) and highest acrolein selectivity (91.7%). The result shows that Cat-α exhibited a lower redox temperature, and possessed a high O_lattice content, which benefit to its excellent oxidant ability. Meanwhile, α-Bi₂Mo₃O₁₂ exhibit rich Co²⁺/Co³⁺ pairs in Cat-α, prompt oxygen migration efficiency, and had a low interaction with propylene confirmed by DFT calculation, which inhibited the excessive oxidation, benefits to acrolein yield. Our study provides a new insight over Bi-Mo catalyst for selective oxidation.

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Optimizing the electronic structure of an electrocatalyst has been supposed to a valid approach to facilitate the hydrogen evolution reaction (HER) activity. Herein, a core–shell architecture comprising a Pt nanoparticle (NP) encapsulated into single-atomic Co species anchored on nickel iron double layered hydroxide substrate (PtCo–NiFe LDH) was established. The PtCo–NiFe LDH catalyst displays the remarkable electrocatalytic HER performance (29 mV@10 mA cm⁻²), better than the NiFe LDH (183 mV@10 mA cm⁻²) and commercial Pt/C (30 mV@10 mA cm⁻²). In addition, it also possesses excellent stability for up to 25 h, and the morphology and structure have hardly undergone any significant changes. It is supposed that the efficient electronic relation between Pt NP and atomically-distributed Co site on NiFe LDH could give rise to plentiful active sites and enhanced conductivity, and thus raise excellent catalytic properties. This work would improve the design and construction of efficient electrocatalysts for a sustainable green energy system.

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The acquired PtCo-NiFe LDH has been successfully prepared and used as HER electrocatalyst

The separation of photo-generated carriers in heterojunctions plays a crucial role in regulating the built-in electric field. The design of materials with directional migration characteristics inside the bulk phase and at the interface between the two phases is of great significance for studying photocatalytic hydrogen evolution. The P-CdS/Ag₂S composite photocatalytic system prepared in this study was doped with P element by heating CdS and NaH₂PO₂ in a muffle furnace, resulting in the directed migration of photo-generated charges in the prepared sample driven by an internal electric field. By in-situ deposition of Ag₂S on the surface of P-CdS, a Janus heterojunction was prepared to enhance the transfer of charge carriers at the phase interface. The hydrogen evolution rate of P-CdS/Ag₂S is 12.44 mmol·h⁻¹·g⁻¹, which is 30 times higher than that of the previously prepared pure CdS sample (0.411 mmol·h⁻¹·g⁻¹). This significant improvement in photocatalytic performance is attributed to the doping of P element and the in-situ loading of Ag₂S co-catalyst, which together promote the effective separation and transport of photogenerated charge carriers, thereby enhancing the photocatalytic activity of the material. This work is of great significance for exploring the charge-directed transfer problem of sulfide photocatalysts in the field of photocatalytic hydrogen evolution.

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Ag/CeO₂ catalysts for the CO oxidation reaction were synthesized by the metal-vapor method. Highly dispersed cerium dioxide used as a carrier was obtained by precipitation of Ce⁺³ ions with various (NH₄OH, (NH₄)₂CO₃ and H₂C₂O₄) precipitators and subsequent calcination in an oxidizing atmosphere. CeO₂ particles were formed with different morphologies depending on the precipitator used. When using NH₄OH, mainly spheroidal particles are formed, while the shape of platelets is typical for the use of H₂C₂O₄. The samples were characterized by EDX, SEM, TEM, XPS, low-temperature nitrogen adsorption. Catalytic testing of the samples was carried out in an oxidation reaction using gas chromatography. It was found that the catalytic activity of the samples decreases in a series Ag/CeO_2carb > Ag/CeO_2oxal > Ag/CeO_2hydr. Ag/CeO_2oxal catalysts demonstrated relatively high activity and the most stable operation over 10 cycles.

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Perovskite-like oxides present huge chemical variability and a wide range of applications as catalysts for oxidation reactions. The interaction of several small gas molecules with the surface of LaCoO₃ and LaMnO₃ perovskite-like oxides was studied by Near Ambient Pressure X-ray photoelectron spectroscopy (NAP-XPS) and CO Temperature Programmed Desorption (CO-TPD). Surface chemical changes such as the O_surf/O_lattice and cation B oxidation state ratios were analyzed as a function of temperature (400 K, 450 K, 500 K, 550 K, and 650 K) under different gas atmospheres like Ar, CO, H₂, and O₂. It was found that there was a partial surface reduction when H₂ and CO were used in the reaction, and therefore, the cation B oxidation state (Mn⁴⁺/Mn³⁺ and Co³⁺/Co²⁺) ratio decreased. Under the CO stream, carbonate species were formed, presenting a C1s signal between 284.5 eV and 287 eV. The CO₂ evolution during the reaction at temperatures greater than 500 K was associated with CO activation over or near to surface oxygen species. A Mars-van Krevelen mechanism was proposed for the process, finding significant differences between LaCoO₃ and LaMnO₃ perovskite-like solid catalysts behavior.

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The hydrogenation of m-cresol was studied across a wide temperature range, revealing complex variations in product distribution and reaction mechanisms. It has been found that the hydrogenation process predominantly yields 3-methylcyclohexanone and 3-methylcyclohexanol as primary products through ring hydrogenation (HYD) within the 140–250 ℃ temperature range. Conversely, the hydrodeoxygenation (HDO) products, toluene and methylcyclohexane, remain insignificant. More interestingly, the HYD yield is observed to diminish at elevated temperatures, with HDO becoming more dominant beyond 270 ℃. Further exploration of potential factors influencing the observed reduction in HYD yield at elevated temperatures—namely site deactivation, equilibrium limitations, and variations in surface coverage—revealed that changes in the surface adsorption of m-cresol play a critical role in the observed decrease in HYD activity, rather than site deactivation or equilibrium constraints. The order of 3-methylcyclohexanone formation with respect to m-cresol increases from 0 to 1 across the examined temperature range, suggesting m-cresol adsorption follows a simple Langmuir–Hinshelwood adsorption model where (r sim k{K}_{C}{P}_{C}/(1+{K}_{C}{P}_{C})). This analysis not only advances our understanding of the temperature-dependent behavior in m-cresol hydrogenation but also lays the groundwork for future kinetic modeling, offering deeper insight into the complex dynamics of m-cresol hydrogenation.

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