Effect of Cu+/Cu2+ Ratio on the Catalytic Behavior of Anhydrous Nieuwland Catalyst during Dimerization of Acetylene

Elucidating the Role of Copper-Induced Mixed Phases on the Electrochemical Performance of Mn-Based Thin-Film Electrodes

Manganese oxide is a fascinating material for use as a thin-film electrode in supercapacitors. Herein, the consequences of copper incorporation on spray pyrolyzed manganese oxide thin films and their electrochemical performance were investigated. The Cu-incorporated manganese oxide thin films were deposited by spray pyrolysis, and their structural and electrochemical properties were thoroughly evaluated. The formation of the spinel Mn3O4 phase with effective Cu incorporation was confirmed by X-ray diffraction investigation. Through Raman studies, it was noticed that mixed phases of manganese oxide tend to form after Cu incorporation, and this result was also reflected in X-ray photoelectron spectroscopic studies. The surface morphology and roughness were also altered by the addition of copper. However, electrochemical measurements implied a reduction in the specific capacitance upon copper inclusion. The cyclic voltammetry test indicated a specific capacitance of 132 F/g for Mn3O4 electrodes, but a substantial drop for copper-incorporated samples due to the mixed manganese phase. The decremental tendency was further supported by galvanostatic charge-discharge studies and electrochemical impedance spectroscopic measurements. These results provide valuable insights into the effects of copper addition in manganese oxide thin-film-based electrodes for energy storage applications.

Initiating Reversible Aqueous Copper-Tellurium Conversion Reaction with High Volumetric Capacity through Electrolyte Engineering

Pursuing conversion-type cathodes with high volumetric capacity that can be used in aqueous environments remains rewarding and challenging. Tellurium (Te) is a promising alternative electrode due to its intrinsic attractive electronic conductivity and high theoretical volumetric capacity yet still to be explored. Herein, the kinetically/thermodynamically co-dominat copper-tellurium (Cu-Te) alloying phase-conversion process and corresponding oxidation failure mechanism of tellurium are investigated using in situ synchrotron X-ray diffraction and comprehensive ex situ characterization techniques. By virtue of the fundamental insights into the tellurium electrode, facile and precise electrolyte engineering (solvated structure modulation or reductive antioxidant addition) is implemented to essentially tackle the dramatic capacity loss in tellurium, affording reversible aqueous Cu-Te conversion reaction with an unprecedented ultrahigh volumetric capacity of up to 3927 mAh cm^-3 , a flat long discharge plateau (capacity proportion of ≈81%), and an extraordinary level of capacity retention of 80.4% over 2000 cycles at 20 A g^-1 of which lifespan thousand-fold longer than Cu-Te conversion using CuSO₄ -H₂ O electrolyte. This work paves a significant avenue for expanding high-performance conversion-type cathodes toward energetic aqueous multivalent-ion batteries.

Deactivation Mechanism and Regeneration of the CuCl/Activated Carbon Catalyst for Gas-Solid Acetylene Dimerization

Acetylene dimerization is necessary to the coal chemical industry for producing monovinylacetylene, while the deactivation mechanism and regeneration of catalysts have not been studied in detail, which is crucial to the design of high-efficiency catalysts for acetylene dimerization. Herein, the deactivation mechanism and regeneration methods of CuCl/activated carbon catalysts in gas-solid acetylene dimerization were studied in detail. The catalysts with different reaction times were analyzed by temperature-programmed desorption of ammonia (NH₃-TPD), Fourier transform infrared (FT-IR), thermogravimetry (TG), pyridine-FTIR, and X-ray photoelectron spectroscopy (XPS) analyses. NH₃-TPD results demonstrated that as the time went on, the strong acid in the samples was enhanced, while the weak acid was weakened. Similarly, pyridine-FTIR results indicated that both Brönsted and Lewis acids in the samples were decreased. TG and XPS results showed that the reasons for deactivation for acetylene dimerization in the gas-solid reaction were significantly affected by coke deposition and the change of Cu valence. The more the content of Cu⁺, the higher the acetylene conversion rate, implying that Cu⁺ may be the active center of the acetylene dimerization reaction. Thus, removing carbon deposition through calcining and increasing the content of Cu⁺ was an effective way of regenerating the catalyst. This work strengthened the understanding of the deactivation behavior and provides a practicable regeneration method for the catalyst in gas-solid acetylene dimerization.

Role of Surface Oxygen Vacancies and Oxygen Species on CuO Nanostructured Surfaces in Model Catalytic Oxidation and Reductions: Insight into the Structure-Activity Relationship Toward the Performance

Defect engineering, such as modification of oxygen vacancy density, has been considered as an effective approach to tailor the catalytic performance on transition-metal oxide nanostructured surfaces. The role of oxygen vacancies (O_V) on the surface of the as-prepared, zinnia-shaped morphology of CuO nanostructures and their marigold forms on calcination at 800 °C has been investigated through the study of model catalytic reactions of reduction of 4-nitrophenol and aerobic oxidation of benzyl alcohol. The O_V on the surfaces of different morphologies of CuO have been identified and quantified through Rietveld analysis and HRTEM, EPR, and XPS studies. The structure-activity relationships between surface oxygen vacancies (O_V) and catalytic performance have been systematically investigated. The enhanced catalytic performance of the cubic CuO nanostructures compared to their as-prepared forms has been attributed to the formation of surface oxygen species on the reactive and dominant (110) surface that has low oxygen vacancy formation energy. The mechanistic role of surface oxygen species in the studied reactions has been quantitatively correlated with the catalytic activity of the different morphological forms of the CuO nanostructures.

Wavelength-Dependent Bifunctional Plasmonic Photocatalysis in Au/Chalcopyrite Hybrid Nanostructures

Excited, or "hot" charge carrier generation and transfer driven by the decay of localized surface plasmon resonances (LSPRs) are key steps in plasmonic photocatalysis. Hybrid structures that contain both metal and semiconductor building blocks facilitate the extraction of reactive charge carriers and their utilization for photoelectrocatalysis. Additional functionality arises from hybrid structures that combine noble metal nanostructures with semiconductor components, such as chalcopyrite (CuFeS2) nanocrystals (NCs), which by themselves support quasistatic resonances. In this work, we use a hybrid membrane to integrate Au nanorods (NRs) with a longitudinal LSPR at 745 nm and CuFeS2 NCs with a resonance peak at 490 nm into water-stable nanocomposites for robust and bifunctional photocatalysis of oxygen and hydrogen evolution reactions in a wavelength-dependent manner. Excitation of NRs or NCs in the nanocomposite correlates with increased hydrogen or oxygen evolution, respectively, consistent with a light-driven electron transfer between the metal and semiconductor building blocks, the direction of which depends on the wavelength. The bifunctional photoreactivity of the nanocomposite is enhanced by Cu(I)/Cu(II)-assisted catalysis on the surface of the NCs.

Dimerization of Acetylene to Monovinylacetylene (MVA) by Bimetallic Zr/Cu Catalyst in Nieuwland Catalytic System

Nieuwland catalyst is a key step in the dimerization of acetylene. Various zirconium metal additives incorporating Nieuwland catalysts were prepared, and their catalytic performances were assessed in acetylene dimerization. Different characterization techniques (i.e., thermogravimetric analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen ion concentration measurement and transmission electron microscopy) were employed in this study. The best catalytic performance was obtained over zirconium-acetylacetonate-incorporated Nieuwland catalysts, with an acetylene conversion of 53.3% and a monovinylacetylene selectivity of 87.4%. Based on these results, the zirconium acetylacetonate additive could reduce the types of transition state complexes, and it could also change the morphology of the catalyst. In addition, the additives could significantly inhibit the occurrence of trimerization products and polymers. Hence, the conversion of acetylene, monovinylacetylene selectivity, and stability of the Nieuwland catalysts were enhanced.

Reaction Mechanism of Simultaneous Removal of H2S and PH3 Using Modified Manganese Slag Slurry

The presence of phosphine (PH3) and hydrogen sulfide (H2S) in industrial tail gas results in the difficulty of secondary utilization. Using waste solid as a wet absorbent to purify the H2S and PH3 is an attractive strategy with the achievement of “waste controlled by waste”. In this study, the reaction mechanism of simultaneously removing H2S and PH3 by modified manganese slag slurry was investigated. Through the acid leaching method for raw manganese slag and the solid–liquid separation subsequently, the liquid-phase part has a critical influence on removing H2S and PH3. Furthermore, simulation experiments using metal ions for modified manganese slag slurry were carried out to investigate the effect of varied metal ions on the removal of H2S and PH3. The results showed that Cu2+ and Al3+ have a promoting effect on H2S and PH3 conversion. In addition, the Cu2+ has liquid-phase catalytic oxidation for H2S and PH3 through the conversion of Cu(II) to Cu(I).

CuFeO2-NiFe2O4 hybrid electrode for lithium-ion batteries with ultra-stable electrochemical performance

Stable electrode materials with guaranteed long-term cyclability are indispensable for advanced lithium-ion batteries. Recently, delafossite CuFeO2 has received considerable attention, due to its relative structural integrity and cycling stability. Nevertheless, the low conductivity of delafossite and its relatively low theoretical capacity prevent its use as feasible electrodes for next-generation batteries that require higher reversible capacities. In this work, we suggest a simple and straightforward approach to prepare CuFeO2-NiFe2O4 by introducing Ni precursor into Cu and Fe precursor to form NiFe2O4, which exhibits higher capacity but suffers from capacity fading, through sol-gel process and subsequent heat treatments. The presence of both NiFe2O4 and CuFeO2 is apparent, and the heterostructure arising from the formation of NiFe2O4 within CuFeO2 renders some synergistic effects between the two active materials. As a result, the CuFeO2-NiFe2O4 hybrid sample exhibits excellent cycling stability and improved rate capability, and can deliver stable electrochemical performance for 800 cycles at a current density of 5.0 A g-1. This work is an early report on introducing a foreign element into the sol-gel process to fabricate heterostructures as electrodes for batteries, which open up various research opportunities in the near future.

Gas–solid acetylene dimerization over copper-based catalysts

A gas–solid acetylene dimerization over copper-based catalysts, with high acetylene conversion and MVA selectivity and convenient operation, was reported.

Effects of Coordination Ability of Nitrogen-Containing Carboxylic Acid Ligands on Nieuwland Catalyst

This article investigated the effect of three nitrogen-containing carboxylic acid ligands for the Nieuwland catalyst system. The catalyst system containing 4.5% N-(2-acetamido) iminodiacetic acid exhibited improved catalytic activity with excellent performance. The yield of monovinylacetylene (MVA) was maintained at 36.7% after 24 h, which was increased by 17.1% relative to the Nieuwland catalyst system. Based on a variety of analyses on the crystals precipitated from the catalyst solutions, it can be inferred that the outstanding performance and lifetime of the catalysts were related to the abilities of these ligands to form strong coordination with Cu+ ions and stabilize them.

Direct reaction between silicon and methanol over Cu-based catalysts: investigation of active species and regeneration of CuCl catalyst

When a CuCl/Si mixture was pretreated at 200–240 °C in a N₂ atmosphere, trimethoxysilane was predominantly formed in the direct reaction of silicon with methanol. When the pretreatment temperatures were raised to 260–340 °C, tetramethoxysilane was favorably formed. The Cu_xSi_yCl_z species catalyzed the reaction between silicon and methanol to trimethoxysilane. Chlorination of the spent CuCl/Si mixture promoted the reaction between silicon and methanol to form both trimethoxysilane and tetramethoxysilane due to the recovery of the CuCl phase and the exposure of the metallic Cu⁰ phase. When Cu₂O, CuO, and Cu⁰ were used as the catalysts, tetramethoxysilane was formed as the main product.

Cu_xSi_yCl_z formed at a lower pretreatment temperature favored trimethoxysilane formation while chlorination of spent CuCl/Si mixture promoted the reaction.