Addition Of Catalyst Research Articles

Ni-Catalyzed Enantioselective Desymmetrization: Development of Divergent Acyl and Decarbonylative Cross-Coupling Reactions.

Ni-catalyzed asymmetric reductive cross-coupling reactions provide rapid and modular access to enantioenriched building blocks from simple electrophile precursors. Reductive coupling reactions that can diverge through a common organometallic intermediate to two distinct families of enantioenriched products are particularly versatile but underdeveloped. Here, we describe the development of a bis(oxazoline) ligand that enables the desymmetrization of meso-anhydrides. When secondary benzylic electrophiles are employed, doubly stereoselective acyl cross-coupling proceeds to give ketone products with catalyst control over three newly formed stereogenic centers. Alternatively, the use of primary alkyl halides in the presence of an additional halogen atom transfer catalyst results in decarbonylative alkylation to give enantioenriched β-alkyl acids. Analysis of reaction rates for a range of both catalysts and substrates supports the notion that tuning the different electrophile activation steps with the two catalysts is required for enhanced reaction performance. These studies illustrate how reaction design can diverge a common Ni-acyl intermediate to either acyl or decarbonylative coupling products and highlight how dual ligand systems can be used to engage unactivated alkyl halides in Ni-catalyzed asymmetric reductive coupling.

In-Situ Polymerization for Catalytic Graphitization of Boronated PAN Using Aluminum and Zirconium Containing Co-Catalysts

In-situ polymerization is an effective method for integrating co-catalysts homogeneously into the polymer matrix. Polyacrylonitrile (PAN)-derived highly graphitized carbon is a state-of-the-art material with diverse applications, including materials for energy storage devices, electrocatalysis, sensing, adsorption, and making structural composites of various technologies. Such highly graphitized materials can be effectively obtained through in-situ polymerization. The addition of external catalysts during in-situ polymerization not only enhances the polymerization rate but also facilitates the degree of graphitization and quality of graphitic carbon upon graphitization at moderate temperatures. In this study, we apply an in-situ polymerization technique to integrate aluminum triflate (Al(OTf)3) and zirconocene dichloride (C5H5)2ZrCl2 co-catalyst into a boronated polyacrylonitrile (B-PAN) matrix. The in-situ polymerization ensures the uniform distribution of the co-catalyst without aggregation, facilitating the formation of a well-ordered graphitic structure at a moderated temperature. Boronated polyacrylonitrile (B-PAN) solutions, with and without co-catalyst (Al(OTf)3, (C5H5)2ZrCl2 or both) were prepared through polymerization process, dried in an oven, and then subjected to graphitization at 1250 °C with a heating rate of 1 °C min−1 for 1 h under an N2 atmosphere. The resulting graphitic carbon was characterized to determine the impact of co-catalyst on the degree of graphitization. This study provides valuable insights into synthesizing high-quality graphitic carbon materials, offering promising pathways for their scalable production through the strategic use of in-situ polymerization and co-catalysis. These materials have potential applications in various fields, including environmental technologies, energy storage, and conversion, offering a pathway to design facile and economical graphitic carbon materials.

Catalytic effect of carbide-forming oxides on the graphitization of carbon objects used in metallurgy

The paper aims to study the possibility of using carbide-forming oxides as catalysts for the graphitization of objects used in metallurgy. Published data on the role of catalysts (carbide-forming metals and their oxides) for the graphitization of carbon materials was analyzed. These graphitization catalysts are shown to be able to significantly reduce the graphitization temperature. The physicochemical properties characteristic of carbon materials graphitized without the use of catalysts are preserved. It was revealed that in the case of bulk materials, the graphitization temperature can be reduced to 1200–1500℃ with the use of catalysts (as opposed to 2000ºС and above). The mechanism of catalytic graphitization involving two reactions is described: interaction between a metal (or its oxide) and carbon with the formation of carbide; subsequent formation of pure metal and carbide-like graphite with increasing temperature. The resulting graphite phase constitutes the crystallization nucleus. The main problem associated with the use of catalysts in the production of graphitized objects was identified—the removal of reaction products, including metals. It is shown that additional catalyst charging can be performed at the stage of mixing and forming, which results in the removal of a part of the reaction products at the stage of baking. The mechanism of removing reaction products is expected to be comparable to ash removal from the piece to be graphitized. It was proven effective for objects to contain carbide-forming oxides, even in insignificant amounts (up to 5 wt%). Due to this, as well as given the possibility of catalyst selection, the negative effect of excessive oxide content in the charge can be reduced depending on further operating conditions. Thus, the use of catalysts for the graphitization of electrodes used in metallurgy is a promising way to reduce the process temperature. However, it is required to select the optimal oxide content and adjust the conditions of electrothermal processes in order to adapt the technology for large-sized products.

Degradation of Triadimefon Compounds in Bayleton 250 EC Pesticides by Sonolysis, Ozonolysis and Sonozolysis

The increase in the agricultural sector is supported by the use of pesticides to kill pests and diseases in plants. However, the continuous use of pesticides in excessive amounts can have a detrimental impact on the environment, especially the waters around agricultural land. Therefore, efforts are needed to degrade pesticide residues containing triadimefon compounds that pollute the environment such as sonolysis, ozonolysis, and sonozoisis methods. These three methods are organic compound degradation methods that utilize OH radicals to degrade organic compounds. Based on the data obtained, the sonolysis method with the addition of TiO2-anatase catalyst produced a degradation percentage of 76.25% after degradation for 150 minutes. While in a much shorter time, namely 15 minutes, using the ozonolysis method without the use of a catalyst, triadimefon can be degraded by 69.10%, and 71.87% with the sonolysis method. Since only a small amount of triadimefon is degraded by the sonozolysis method, it is more effective to use the ozonolysis method to degrade this triadimefon compound.

Catalytic Pyrolysis of Plastic Waste using Red Mud and Limestone: Pyrolytic Oil Production and Ignition characteristics

This study investigated the catalytic pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE) using 10 wt.% red mud and 10 wt.% limestone catalysts in a batch reactor. The process was conducted at an operating temperature of 350°C with retention times of 30, 60, and 90 minutes. The effects of adding red mud and limestone catalysts on the yields of liquid, solid, and gas pyrolysis products were analyzed. The pyrolytic oil was further evaluated using droplet evaporation measurements, equipped with a K-type thermocouple and a CCD camera to monitor droplet evolution within an atmospheric chamber. The addition of catalysts enhanced the liquid product yield while reducing the solid yield. The catalytic pyrolysis successfully facilitated the isomerization of plastic polymers, breaking the carbon chains of PP with 10 wt.% red mud. Olefin content increased by up to 7.3% for both 10 wt.% red mud and 10 wt.% limestone. Furthermore, the evaporation rate constant of the catalytic pyrolysis oils improved by up to 8.3%. This study aims to provide new insights into utilizing local waste materials to enhance the quality of pyrolytic plastic products.

BINAP-Accelerated Copper-Mediated Photochemical Late-Stage Trifluoromethylation of Arenes.

Site-selective and late-stage C-H trifluoromethylation (including pentafluoroethylation) of arylthianthrenium salts using in situ generated CuCF3 from Ruppert-Prakash reagent under visible light was found to be significantly accelerated by a catalytic amount of rac-BINAP, allowing the reaction to complete within 15 min under very mild conditions without using any additional photoredox catalysts. The process showed a broad substrate scope, high efficiency, and excellent regioselectivity, which holds the promise to accelerate the discovery of fluorinated medicinal compounds.

Preparation of Bioethanol from Pineapple Peel (ananas comosus L. Mer) Waste with the Addition of Hydrochloric Acid and Citric Acid Catalysts

Bioethanol is ethanol derived from biological sources. Bioethanol can be produced from plants that contain many starch and cellulose compounds using the help of yeast activity. One of them is pineapple peel which can add a variety of basic materials for bioethanol production which is economical and easy to obtain. This study aims to analyze the effect of acid hydrolysis on glucose content, analyze the effect of fermentation time and the effect of yeast weight on bioethanol characteristics. This research has been done before and only focused on one catalyst. What has never been done is comparing the two catalysts. The research was conducted using hydrolysis fermentation and distillation using hydrochloric acid and citric acid catalysts with yeast weight variation of 12, 15, and 17 grams, fermentation time variation of 2, 3, 4, and 5 days. In this research, glucose test, density analysis, yield analysis, and GC-MS were conducted. The results of this study showed that the best results in the treatment of hydrochloric acid catalyst at a yeast weight of 15 grams, and obtained glucose levels of 6.90% for hydrochloric acid and 5.10% for citric acid, density test obtained the highest results at a yeast weight of 15 grams 4 days 0.8288 gr / ml for hydrochloric acid catalyst and the lowest density obtained at a yeast weight of 17 grams 5 days 0, 8168 gr/ml, yield analysis obtained at the amount of 15 grams of yeast with a fermentation time of 14 days of 4.3536% in the treatment of hydrochloric acid catalyst and 3.8557% in the treatment of citric acid catalyst fermentation time of 3 days, GC-MS test showed that ethanol contained in the test sample.

Nuplon: New synthetic polymers fully degradable in water

New crosslinked polyesters, which are fully degradable in the presence of water over several months in the environment, were synthesized by direct polyesterification of multi-hydroxylic alcohols (e.g., pentaerythritol or glycerol), multi-carboxylic acids (e.g., citric acid), and hydroxy acid compounds (e.g., lactic acid). The reaction produced a crosslinked matrix with mechanical properties of solid and useful degradability in the environment. This reaction can be performed with moderate heat (100–200 °C) and without requiring the aid of additional catalysts, inert gas, or vacuum. The crosslinked matrix can be thermoplastic or thermoset, depending on the extent of crosslinking, which is controlled by reaction time and temperature. The polyesters formed with various ratios of the monomers degrade in water in 12 h at 95 °C, 3 days at 70 °C, and about 3 months at 30 °C. These environmentally degradable alkyl polyesters include a range of mechanical strengths and elasticity, making them suitable for various applications. These environmentally degradable, synthetic polymers can replace current non-degradable polymers in various applications. These new polymers are named “Nuplons”.

Microwave Mediated Acylation of Alcohols, Phenols and Thiophenols in Neat Acetic Anhydride.

A microwave-based method for the acylation of alcohols, phenols, and thiols has been developed without the need of a catalyst or base additives. The reaction is far more rapid than previously reported acylation methods, tolerates a wide variety of functional groups, and provides easy isolation of products in excellent yields without the need for chromatography. Most products can be isolated directly via evaporation under reduced pressure or by pouring the reaction mixture into water and filtering.

Cyclic natural product oligomers: diversity and (bio)synthesis of macrocycles.

Cyclic compounds are generally preferred over linear compounds for functional studies due to their enhanced bioavailability, stability towards metabolic degradation, and selective receptor binding. This has led to a need for effective cyclization strategies for compound synthesis and hence increased interest in macrocyclization mediated by thioesterase (TE) domains, which naturally boost the chemical diversity and bioactivities of cyclic natural products. Many non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) derived natural products are assembled to form cyclodimeric compounds, with these molecules possessing diverse structures and biological activities. There is significant interest in identifying the biosynthetic pathways that produce such molecules given the challenge that cyclodimerization represents from a biosynthetic perspective. In the last decade, many groups have pursued the characterization of TE domains and have provided new insights into this biocatalytic machinery: however, the enzymes involved in formation of cyclodimeric compounds have proven far more elusive. In this review we focus on natural products that involve macrocyclization in their biosynthesis and chemical synthesis, with an emphasis on the function and biosynthetic investigation on the special family of TE domains responsible for forming cyclodimeric natural products. We also introduce additional macrocyclization catalysts, including butelase and the CT-mediated cyclization of peptides, alongside the formation of cyclodipeptides mediated by cyclodipeptide synthases (CDPS) and single-module NRPSs. Due to the interdisciplinary nature of biosynthetic research, we anticipate that this review will prove valuable to synthetic chemists, drug discovery groups, enzymologists, and the biosynthetic community in general, and inspire further efforts to identify and exploit these biocatalysts for the formation of novel bioactive molecules.

Dynamic Multi-Physics Modelling of a PEM Stack for a Digital Twin Application

Electrolysis plants producing green hydrogen often face fluctuating renewable power availability and prices. Proton-Exchange-Membrane (PEM) electrolysis technology offers a potential solution, as fast dynamic load changes are possible. With expeditious adjustments to the power availability, a PEM plant can contribute to grid stability while using economically attractive excess power. Alternatively, adapting to fluctuating product demands can reduce the required energy for intermediate storage of hydrogen in liquid form or in pressure tanks.To consistently operate the plant at the optimal load point, precise monitoring of plant performance, integrity, and state is vital. A digital twin running concurrently with the plant increases the available information of the stack data, as well as it simultaneously offers a platform to engage in anomaly detection and diagnosis processes. The goal is to increase reliability, availability, and maintainability, which is made possible through data provided by virtual sensors (calculated sensor values from the digital twin).With a digital twin, critical states of non-measurable conditions in a PEM cell, such as hydrogen crossover, temperature gradients, or the state of degradation, can be determined and addressed in real-time. With all additional information accessible, the digital twin can visualize plant operation and helps in determining efficient transitions between operating points, augmenting plant operation and optimally utilizing the PEM plant’s load flexibility.To leverage these advantages, a digital twin is developed for PEM electrolysis plants. Its structure consists of a dynamic plant model, an interface to the plant, and a state estimation algorithm. The modelling focus lies on the PEM stacks, for which a detailed dynamic multi-physics model is developed. It is structured into the submodels of mass transport, voltage, temperature, and pressure, which combine into an equation-based model solved by a DAE solver. Main features are the membrane discretization for mass transport via the Stefan-Maxwell equations and the one-dimensionally resolved temperature profile across the cell. The voltage model is represented in form of an equivalent circuit, modelling the electric effects of each individual cell layer.Validation and results of the dynamic model are shown, especially highlighting the interaction and dependencies between the sub-models. The mass transport model shows non-linear concentration profiles of crossover components inside the membrane. Consequently, an assessment of the different positions of additional recombination catalyst layers inside the membrane is presented, including the influence of different operating conditions and dynamic loads. Following, temperature profiles across the cell and dynamic voltage responses for operation are shown. All results are discussed in the context of a simulated PEM electrolysis plant in dynamic operation, which is especially expedient concerning automatic load change and automatic start-up strategies.

Electrocatalytic Functionalized Specialty Paper As Low-Cost Porous Transport Layer Material in CO2-Electrolysis

Efficiently harnessing excess atmospheric carbon dioxide (CO2) is crucial for closing the carbon cycle effectively. Electrochemical CO2 reduction (ECR) holds significant promise for producing valuable products and environmentally friendly chemicals. Carbon monoxide (CO) stands out as one of the most economically viable products of ECR.[1,2] While noble metals commonly catalyze CO2-to-CO conversion, alternative non-noble catalysts are essential for cost reduction. Molecular catalysts like cobalt phthalocyanine (CoPc) offer high ECR activity but limited stability (< 10 h).[3–5] Moreover, the production cost of porous transport layers (PTLs) significantly impacts ECR electrolyzer costs, with commercial carbon-PTLs adding a 20% increase.[6–8] Our work focuses on developing low-cost, non-woven cellulose-based porous PTLs for electrochemical CO2-to-CO conversion. By depositing a cobalt phthalocyanine (CoPc) catalyst layer over our PTLs, we fabricated ECR-functioning gas-diffusion-electrodes (GDEs) for both flow-cell and zero-gap electrolyzers. Under optimal conditions, the Faradaic efficiency of CO (FECO) reached 92 % at a high current density of 200 mA cm−2. Furthering the architecture of the GDEs, CoPc was incorporated into the initial PTL slurry, forming ECR-active PTLs without the need for an additional catalyst layer. The new GDE architecture favored the CoPc-distribution by enhancing the contact and interactions with the carbon substrate and demonstrated a stable electrolysis process for over 50 h in a zero-gap electrolyzer at 200 mA cm−2 with a FECO of 80 %.[9] This study marks a substantial breakthrough in developing for the first time, paper-based functionalized PTLs for the ECR. Marking a significant contribution to the progression of the ECR into practical implications.[1] M. Jouny, W. Luc, F. Jiao, Ind. Eng. Chem. Res. 57 (2018) 2165–2177.[2] G.O. Larrazábal, A.J. Martín, J. Pérez-Ramírez, J. Phys. Chem. Lett. 8 (2017) 3933–3944.[3] S. Ren, D. Joulié, D. Salvatore, K. Torbensen, M. Wang, M. Robert, C.P. Berlinguette, Science 365 (2019) 367–369.[4] C. Costentin, S. Drouet, M. Robert, J.-M. Savéant, Science 338 (2012) 90–94.[5] M. Wang, K. Torbensen, D. Salvatore, S. Ren, D. Joulié, F. Dumoulin, D. Mendoza, B. Lassalle-Kaiser, U. Işci, C.P. Berlinguette, M. Robert, Nat. Commun. 10 (2019) 3602.[6] A.J. Navarro, M.A. Gómez, L. Daza, J.J. López-Cascales, Sci. Rep. 12 (2022) 4219.[7] B. Yarar Kaplan, L. Işıkel Şanlı, S. Alkan Gürsel, J. Mater. Sci. 52 (2017) 4968–4976.[8] R.I. Masel, Z. Liu, H. Yang, J.J. Kaczur, D. Carrillo, S. Ren, D. Salvatore, C.P. Berlinguette, Nat. Nanotechnol. 16 (2021) 118–128.[9] I. Stamatelos, M. Rentzsch, C. Liu, F. Bauer, S. Barwe, M. Robert, ChemCatChem n/a (n.d.) e202300980. Figure 1

Understanding the Impact of Porous Transport Layers on Anion Exchange Membrane Electrolyzer Performance

Anion exchange membrane water electrolysis (AEMWE) is a promising technology for the low-cost production of green hydrogen. However, significant improvements in components and component integration are needed to improve the efficiency and lifetime of AEMWE devices. [1] The anode catalyst layer is critical to activity due to the large overpotentials associated with the sluggish kinetics of the oxygen evolution reaction (OER) and to durability due to the highly oxidizing environment that can lead to catalyst and polymer degradation. The anodic overpotential can be improved by increasing the number of catalyst sites that are utilized for the reaction, which requires the formation of uniform catalyst layers with good interfaces with both the membrane and the porous transport layer (PTL). [2] The PTL serves several important roles in the electrolyzer, including the transport of electrons between catalyst sites and the current collector and the transport of gaseous products out of the catalyst layer. The PTLs used for AEMWE are typically Ni-based, with no precious metal coating or microporous layer. The morphology of the PTL impacts its interface with the catalyst layer, which affects in-plane electronic resistance and the ability to utilize catalyst sites effectively. [3] The porosity and pore size of the PTL also affect bubble removal, which can contribute significantly to mass transport overpotential, particularly at high current densities. Commercially available PTLs are often not designed for the AEMWE application, meaning that their properties are not optimized for these two critical functions. In addition, in a supporting electrolyte like potassium hydroxide, hydroxide ions are not restricted to the catalyst layer-membrane interface or to the ionomer network such that the PTL also contributes to catalytic activity. Ni alloy PTLs can provide an advantage of higher initial catalytic activity compared to standard Ni, but many dopant metals (i.e., Fe, Cr, etc.) are prone to dissolution under AEMWE operating conditions, which can damage the membrane and lead to higher rates of degradation. Improved PTL designs are needed to improve electrolyzer performance and durability.In this study, we investigate the impact of PTLs with varying morphology and composition on kinetics, catalyst layer resistance, and durability. The properties of the PTLs, including composition, crystal structure, thickness, porosity, and fiber dimensions are determined using spectroscopy, diffraction, electron microscopy, and micro X-ray tomography. These material properties are then correlated with the performance of the PTL, with and without an additional catalyst layer. As shown in Figure 1, the PTLs have a significant effect on device performance and often have significant electrochemical activity in the absence of a catalyst layer. The impact of the PTL on performance trends with catalyst conductivity and loading is also explored. Electrochemical impedance spectroscopy (EIS) is further used to understand the effect of the PTL on interfacial charge resistance and resistances within the catalyst layer. Finally, ex situ characterization of the catalyst layer and PTL with scanning electron microscopy and X-ray spectroscopy, as well as analysis of dissolved species in the electrolyte using an inductively coupled-mass spectrometer (ICP-MS), are used to understand the material stability of the PTL and impacts of PTL degradation on overall durability. This work provides insight into PTL design principles, which can be used to improve the performance and lifetime of AEM electrolyzers.

Multi-Scale Computational Fluid Dynamics Simulation of Alkaline Water Electrolyzers: A Numerical Investigation

The utilization of water electrolyzers for hydrogen production represents one of the promising technologies in the global transition away from fossil fuels towards sustainable energy sources. Among the various types of electrolyzers, alkaline electrolyzers in the zero-gap configuration with different separator types, like diaphragms and anion conducting membranes, have garnered significant attention, among others, due to their potential to utilize non-precious metal catalysts such as iron and nickel for the electrodes. This characteristic holds promise for reducing costs and increasing accessibility to hydrogen production technologies, including the establishment of largescale stationary systems and hydrogen production powered by renewable energy.In order to accelerate the development process and to understand the important mechanisms in more detail within these cell types, numerical Computational Fluid Dynamics (CFD) simulations are conducted and combined with experimental cell testing at the Juelich Research Center. The studies focus on investigating the influence of variations in the porous transport anode-electrode, particularly nickel fiber fleece and nickel foam, along with their characteristic properties on the performance of the anion exchange membrane water electrolysis cells. This includes investigating porosity gradients, optional additional catalyst layers and their loadings, and the effects of changing types and thicknesses of porous transport electrodes. These studies are conducted at varying electrolyte concentrations and operating conditions.Using the open-source platform OpenFOAM® and the developed libraries of OpenFuelCell21, CFD simulations are performed at both the micro and meso scales to examine the aforementioned questions (see Fig. 1).The model incorporates all key transport phenomena, such as two-phase fluid flow, described via an Eulerian-Eulerian approach, heat and mass transfer, electrochemical reactions, species transfer, and charge transfer across the various functional layers of the cell. It allows for the analysis of electrochemical reactions by employing the Butler-Volmer equation to describe electrokinetics across various types of electrochemically active porous electrodes.For the multi-physical simulation of the detailed flow within the porous electrodes at micro scale, microtomography images are used as geometrical input. In addition, the microscopic data are subsequently utilized for characterizing the porous electrodes in the macro-homogeneous simulations performed at the meso-scale.Literature: Zhang, S. Hess, H. Marschall, U. Reimer, S. Beale, W. Lehnert, openFuelCell2: A new computational tool for fuel cells electrolyzers, and other electrochemical devices and processes, Comput. Phys. Commun. 298 (2024) 109092. Figures:Figure 1: Numerical simulation of the flow through different micro-porous electrodes (left) which results are used for the macro-homogeneous simulations of alkaline electrolysis cell in 2-D and 3-D (right). Figure 1

Effect of La–Ni@3DG catalyst concentration on the hydrogen storage properties of MgH2

This research paper explores the influence of varying the quantity of La–Ni@3DG catalyst on the hydrogen storage capabilities of MgH2. La–Ni@3DG catalyst was prepared using lanthanum chloride heptahydrate and nickel chloride hexahydrate as raw materials combined with three-dimensional graphene, then mixed with MgH2 via ball milling to prepare MgH2 + x wt.% La–Ni@3DG (x = 0, 3, 5, 7) composite alloy. X-ray diffraction analysis showed that the composite alloy was mainly composed of the MgH2 phase, with the presence of Mg and (La, Ni) phases detected. With increased La–Ni@3DG addition, the broadening of the MgH2 diffraction peak significantly improved, indicating the catalyst promoted alloy phase structure uniformity and crystallinity. The composite alloy forms new phases such as LaH3, LaNi3H6, and Mg2NiH4 during hydrogen absorption. These phases cooperate with in-situ formed LaH3 and Mg2Ni to significantly improve the reversible hydrogen absorption and desorption properties of MgH2. Adding La–Ni@3DG catalyst has a significant positive effect on the hydrogen absorption and desorption of MgH2, leading to a considerable improvement. At 553 K, the composite alloy reaches hydrogen absorption equilibrium faster than pure MgH2, and the temperature for hydrogen absorption is significantly reduced to 373 K. The dehydrogenation performance is also improved, with 5 wt.% La–Ni@3DG is showing the best dehydrogenation performance at 553 K. The initial dehydrogenation temperature commences at approximately 505 K, while the dehydrogenation activation energy attains its minimum value: a remarkably low 109.91 kJ/mol H2. Additionally, the addition of catalyst reduces the pressure of the hydrogen absorption and desorption platform, effectively reducing the hysteresis effect during hydrogen absorption and desorption when the catalyst content is 5 wt.%, the enthalpy change and entropy change of the composite alloy reach a minimum, −70.45 kJ/mol H2 and 74.38 kJ/mol H2 (hydrogen absorption), −101.93 J/K/mol H2 and 103.68 J/K/mol H2 (hydrogen desorption), respectively.

Controlled preparation of cellulose acetate by deep eutectic solvent homogeneous catalysis

This work proposed a homogeneous preparation strategy of cellulose acetate by using a deep eutectic solvent consisting of zinc chloride/phosphoric acid/water (ZnCl2/PA/H2O). The results showed that the DES (the molar ratio of ZnCl2: PA: H2O = 1:1:3) had good solubility for bamboo pulp with high degree of polymerization. The dynamic dissolution behavior of cellulose in DES was also studied. Cellulose was first moistened and swollen and then dissolved. The crystalline state of cellulose changed from type I to type II after regeneration. Under the synergistic effect of acetic anhydride (Ac2O), the dissolved cellulose in DES could be uniformly acetylated. The effects of temperature, reaction time and molar ratio of Ac2O/anhydrous glucose on degree of substitution (DS) were investigated in their respective ranges (30–50 °C, 2–10 h and 4–24). Cellulose acetate with DS of 0.42–1.81 was successfully prepared. The substituent distribution of the sample was analyzed as C-6 > C-2 > C-3. Moreover, the entire process required no additional catalysts or activation steps, reducing the difficulty of solvent recovery. The insight from this study provides a new idea for the development of greener methods for the homogeneous preparation of cellulose acetate.

Anomalous CatalyticPerformance on Non-Active-Site Carbon Substrate.

Carbon-based nanomaterials are gaining attention in electrocatalysis. This study investigates the inherent nitrate reduction activity (NO3RR) of commercial carbon paper as a substrate. Results showed that carbon paper, without additional catalysts, achieved approximately 80.42% NH3Faradaic efficiency (FE) at -2.1 V vs. Hg/HgO in alkaline conditions, 83.51% NH3FE at -1.9 V vs. Ag/AgCl in neutral conditions, and 14.53% NH3FE at -1.9 V vs. MSE in acidic conditions. Density Functional Theory (DFT) calculations revealed energy barriers of 2.66 eV, 0.95 eV, and 1.37 eV, respectively. Molecular physisorption on the carbon paper surface generates an induced electric field, promoting charge transfer between the carbon paper and the adsorbed molecules, thus enhancing the activity of the carbon paper. These findings highlight the importance of considering the intrinsic catalytic properties of carbon substrates in catalyst design and evaluation, as overlooking these properties can lead to inaccurate performance assessments. This study emphasizes the need for a comprehensive approach to optimize catalytic systems.

Molecular Copper-Anthraquinone Photocatalysts for Robust Hydrogen Production.

The development of robust and inexpensive photocatalysts for H2 production under visible light irradiation remains a significant challenge. This study presents a series of square planar copper anthraquinone complexes (R4N)CuL2 (R = ethyl, L = alizarin dianion (CuAA); R = n-butyl, L = purpurin dianion (CuPP), (2-hydroxyanthraquinone)formamide dianion (CuAHA)) as molecular photocatalysts to achieve high long-term stability in visible-light-driven H2 production. These complexes are self-sensitized by the anthraquinone ligands and serve as proton reduction photocatalysts without additional photosensitizers or catalysts. Under irradiation of blue light, complex CuAA produces H2 in a mixture of H2O/DMF with undiminished activity over 42 days, giving a turnover number exceeding 6800. Electrochemical and UV-vis studies are consistent with an EECC mechanism (E: electron transfer and C: protonation) in the catalytic cycle. The initial photochemical steps involve conversion of both anthraquinone ligands to hydroquinones. Further light-driven reductions of the hydroquinones followed by two protonation steps results in formation of H2. Dependence of the catalytic rate on the concentration of H2O suggests that either the generation of a CuII-H intermediate by protonation or heterocoupling between CuII-H and H+ to produce H2 is the turnover-limiting step in catalysis.

Aromatic Poly(dithioacetal)s: Spanning Degradability, Thermostability, and High Refractive Index Towards Eco-friendly Optics.

In the quest for eco-friendly optics, high refractive index polymers (HRIPs) with degradability have been one of the desirable optical materials for realizing eco-friendly and efficient lighting technologies. However, it has been challenging for HRIPs to simultaneously realize thermostability, high refractive index (RI), visible transparency, and efficient degradability, all of which are essential for their practical use. In this context, we herein focus on aromatic poly(dithioacetal)s, composed of visible-transparent yet degradable dithioacetal moieties and rigid phenylene sulfide spacers, exhibiting moderately high Tg (> 60 °C), high RI (> 1.7), and colorless film features. In addition, poly(dithioacetal)s can balance (1) high stability under the operating conditions even upon heating and (2) quantitative degradability that can selectively yield cyclic low-molecular-weight products that can be further repolymerized upon further addition of an acid catalyst. These results provide a key concept for high refractive index polymers that allow on-demand degradability and recyclability without compromising their high potential thermal and optical properties.

State-of-the-art Advances in the Ignition Selay Reduction of N,N-dimethylethanamine

Propellant is a core fuel in defense and aerospace applications. However, conventional hydrazine fuel is highly volatile, toxic, and carcinogenic, resulting in huge threats to the human body and environment. N,N-dimethylethanamine (DMAZ) is a green, high-energy fuel with a low freezing point, high density, high specific impulse, and high combustion rate, and it is a promising substitute of conventional hydrazine fuel. Nevertheless, the industrial application of DMAZ is limited by long ignition delay. In this study, the mechanism of ignition of DMAZ was explored by summarizing current methods to reduce the ignition delay of DMAZ, including the addition of catalyst, fuel formulation, and tuning molecular structure. This study provides references for applications of amine azide.