Production of H2 and Glucaric Acid Using Electrocatalyst Glucose Oxidation by the Ta NiFe LDH Electrode.

The slow anodic oxygen evolution reaction (OER) significantly limits electrocatalytic water splitting for hydrogen production. We proposed the electrocatalyst for glucose oxidation by Ta-doping NiFe LDH nanosheets to simultaneously obtain glucaric acid (GRA) and hydrogen gas as a useful byproduct. Superior glucose oxidation reaction (GOR) activity is demonstrated by the optimized Ta-NiFe LDH, which has a low overpotential of 192 mV, allowing for a small Tafel slope of 70 mV dec-1 and a current density of 50 mA cm-2. The Ta NiFe LDH-oxidized glucose to GRA with a 72.94% yield and 64.3% Faradaic efficiency at 1.45 VRHE. Herein, we report the Ta NiFe LDH/NF electrode for the GOR&hydrogen evolution reaction (HER), which exhibits a cell voltage of 1.62 V to reach a current density of 10 mA cm-2, which is 250 mV lower compared to OER&HER (1.87 V). This study reveals that GOR is an energy-efficient and cost-effective method for producing H2 and valorizing biomass.

A systematic review on green and natural polymeric nanofibers for biomedical applications.

Electrospinning is the simplest technique to produce ultrathin nanofibers, which enables the use of nanotechnology in various applications. Nanofibrous materials produced through electrospinning have garnered significant attention in biomedical applications due to their unique properties and versatile potential. In recent years, there has been a growing emphasis on incorporating sustainability principles into material design and production. However, electrospun nanofibers, owing to their reliance on solvents associated with significant drawbacks like toxicity, flammability, and disposal challenges, frequently fall short of meeting environmentally friendly standards. Due to the limited solvent choices and heightened concerns for safety and hygiene in modern living, it becomes imperative to carefully assess the implications of employing electrospun nanofibers in diverse applications and consumer products. This systematic review aims to comprehensively assess the current state of research and development in the field of "green and natural" electrospun polymer nanofibers as well as more fascinating and eco-friendly commercial techniques, solvent preferences, and other green routes that respect social and legal restrictions tailored for biomedical applications. We explore the utilization of biocompatible and biodegradable polymers sourced from renewable feedstocks, eco-friendly processing techniques, and the evaluation of environmental impacts. Our review highlights the potential of green and natural electrospun nanofibers to address sustainability concerns while meeting the demanding requirements of various biomedical applications, including tissue engineering, drug delivery, wound healing, and diagnostic platforms. We analyze the advantages, challenges, and future prospects of these materials, offering insights into the evolving landscape of environmentally responsible nanofiber technology in the biomedical field.

Electrocatalytic Reactions for Converting CO2 to Value-Added Products: Recent Progress and Emerging Trends.

Carbon dioxide (CO2) emissions are an important environmental issue that causes greenhouse and climate change effects on the earth. Nowadays, CO2 has various conversion methods to be a potential carbon resource, such as photocatalytic, electrocatalytic, and photo-electrocatalytic. CO2 conversion into value-added products has many advantages, including facile control of the reaction rate by adjusting the applied voltage and minimal environmental pollution. The development of efficient electrocatalysts and improving their viability with appropriate reactor designs is essential for the commercialization of this environmentally friendly method. In addition, microbial electrosynthesis which utilizes an electroactive bio-film electrode as a catalyst can be considered as another option to reduce CO2. This review highlights the methods which can contribute to the increase in efficiency of carbon dioxide reduction (CO2R) processes through electrode structure with the introduction of various electrolytes such as ionic liquid, sulfate, and bicarbonate electrolytes, with the control of pH and with the control of the operating pressure and temperature of the electrolyzer. It also presents the research status, a fundamental understanding of carbon dioxide reduction reaction (CO2RR) mechanisms, the development of electrochemical CO2R technologies, and challenges and opportunities for future research.

Photoelectrochemical Epoxidation of Cyclohexene on an α-Fe2O3 Photoanode Using Water as the Oxygen Source.

This study developed a safe and sustainable route for the epoxidation of cyclohexene using water as the source of oxygen at room temperature and ambient pressure. Here, we optimized the cyclohexene concentration, volume of solvent/water (CH3CN, H2O), time, and potential on the photoelectrochemical (PEC) cyclohexene oxidation reaction of the α-Fe2O3 photoanode. The α-Fe2O3 photoanode epoxidized cyclohexene to cyclohexene oxide with a 72.4 ± 3.6% yield and a 35.2 ± 1.6% Faradaic efficiency of 0.37 V vs Fc/Fc+ (0.8 VAg/AgCl) under 100 mW cm-2. Furthermore, the irradiation of light (PEC) decreased the applied voltage of the electrochemical cell oxidation process by 0.47 V. This work supplies an energy-saving and environment-benign approach for producing value-added chemicals coupled with solar fuel generation. Epoxidation with green solvents via PEC methods has a high potential for different oxidation reactions of value-added and fine chemicals.

Development of Low-Shrink Epoxy Putty to Solve Appearance-Quality Defects of Carbon-Fiber-Reinforced Plastic Automotive Exterior Parts.

In this study, epoxy putties with novel compositions were developed for the filling of structural voids in carbon-fiber-reinforced plastics (CFRPs), which are used to fabricate automotive parts. Two constituent solutions-one consisting of epoxy resins and the other consisting of a hardener-were formulated, mixed, and then coated on CFRP surfaces, followed by curing. The surfaces were then evaluated to determine the shrinkage rates (calculated based on the liquid densities and cured mixtures), adhesion properties (determined by a peel test), and color differences (measured with a colorimeter) of the synthesized putties. The last two properties were compared with those of the commercially available putties to ascertain the thermal resistance of the developed putties. The results indicated that the synthesized epoxy putties were more strongly adhesive and exhibited less difference in color. Furthermore, after thermal impact, both the adhesive properties and color stabilities of the synthesized epoxy putties were found to be superior to those of the commercial putty.

Synthesis of Waterborne Polyurethane Using Phosphorus-Modified Rigid Polyol and its Physical Properties.

In this study, a phosphorous-containing polyol (P-polyol) was synthesized and reacted with isophorone diisocyanate (IPDI) to produce water-dispersed polyurethane. To synthesize waterborne polyurethanes (WPUs), mixtures of P-polyol and polycarbonate diol (PCD) were reacted with IPDI, followed by the addition of dimethylol propionic acid, to confer hydrophilicity to the produced polyurethane. An excess amount of water was used to disperse polyurethane in water, and the terminal isocyanate groups of the resulting WPUs were capped with ethylene diamine. P-polyol:PCD molar ratios of 0.1:0.9, 0.2:0.8, and 0.3:0.7 were used to synthesize WPUs. The films prepared by casting and drying the synthesized WPUs in plastic Petri dishes were used to test the changes in physical properties induced by changing the P-polyol:PCD molar ratio. The experimental results revealed that the tensile strength of PU-10, the WPU with a P-polyol:PCD molar ratio of 0.1:0.9, was 16% higher than that of the reference P-polyol-free WPU sample. Moreover, the thermal decomposition temperature of PU-10 was 27 °C higher than that of the reference sample.

Redox-Initiated Reversible Addition-Fragmentation Chain Transfer (RAFT) Miniemulsion Polymerization of Styrene using PPEGMA-Based Macro-RAFT Agent.

Redox-initiated reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerizations are successfully conducted with an employment of trithiocarbonate-based macro-RAFT agents and surfactant. Two macro-RAFT agents-hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA27 ) and amphiphilic poly(poly(ethylene glycol) methyl ether methacrylate)-b-polystyrene (PPEGMA27 -b-PS33 )- are examined for the miniemulsion polymerization of styrene. The use of PPEGMA27 (in the presence of sodium dodecyl sulfate (SDS)) results in a slow polymerization rate with a broad particle size. In the absence of SDS, the use of PPEGMA27 -b-PS33 results in a broad particle size distribution due to its inability to form uniform initial droplets whereas the same amphiphilic block copolymer in the presence of SDS yields resulting products with a uniform particle size distribution. The latter exhibits a fashion of controlled polymerization with a high consumption of monomer (98% in 100 min) and a narrow molecular weight distribution throughout the polymerization. This is attributed to the formation of uniform droplets facilitated by SDS in a miniemulsion. The amphiphilic macro-RAFT agent is able to anchor efficiently on the monomer droplet or particle/water interface and form stabilized particles of well-defined PPEGMA27 -b-PS block copolymer, confirmed using dynamic light scattering and transmission electron micrographs.

Flame Retardant Submicron Particles via Surfactant-Free RAFT Emulsion Polymerization of Styrene Derivatives Containing Phosphorous.

The reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of diethyl-(4-vinylbenzyl) phosphate (DEVBP) was performed using PEG-TTC as a macro RAFT agent. PEG-TTC (MW 2000, 4000) was synthesized by the esterification of poly (ethylene glycol) methyl ether with a carboxylic-terminated RAFT agent, composed a hydrophilic poly (ethylene glycol) (PEG) block and a hydrophobic dodecyl chain. The RAFT emulsion polymerization of DEVBP was well-controlled with a narrow molecular size distribution. Dynamic light scattering and confocal laser scanning microscopy were used to examine the PEG-b-PDVBP submicron particles, and the length of the PEG chain (hydrophilic block) was found to affect the particle size distribution and molecular weight distribution. The submicron particle size increased with increasing degree of polymerization (35, 65, and 130), and precipitation was observed at a high degree of polymerization (DP) using low molecular weight PEG-TTC (DP 130, A3). The flame retardant properties of the PEG-b-PDVBP were evaluated by thermogravimetric analysis (TGA) and micro cone calorimeter (MCC). In the combustion process, the residue of PEG-b-PDEVBP were above 500 °C was observed (A1 ~ B3, 27 ~ 38%), and flame retardant effect of PEG-b-PDEVBP submicron particles/PVA composite were confirmed by increasing range of temperature and decreasing total heat release with increasing contents of PEG-b-PDEVBP. The PEG-b-PDEVBP submicron particles can provide flame retardant properties to aqueous, dispersion and emulsion formed organic/polymer products.

Modified Epoxy Resin Synthesis from Phosphorus-Containing Polyol and Physical Changes Studies in the Synthesized Products.

Epoxy resins are commonly used to manufacture the molding compounds, reinforced plastics, coatings, or adhesives required in various industries. However, the demand for new epoxy resins has increased to satisfy diverse industrial requirements such as enhanced mechanical properties, thermal stability, or electrical properties. Therefore, in this study, we synthesized new epoxy resin (PPME) by modifying phosphorous-containing polyol. The prepared resin was analyzed and added to epoxy compositions in various quantities. The compositions were cured at high temperatures to obtain plastics to further test the mechanical and thermal properties of the epoxy resin. The measured tensile and flexural strength of epoxy compositions were similar to the composition without synthesized epoxy resin. However, the heat release rates of the compositions exhibited tendencies of a decrease proportional to the amount of PPME.

Mechanical and Thermal Properties of Epoxy Composites Containing Zirconia-Impregnated Halloysite Nanotubes with Different Loadings.

Epoxy resins are widely used in various industrial fields due to their low cost, good workability, heat resistance, and good mechanical strength. However, they suffer from brittleness, an issue that must be addressed for further applications. To solve this problem, additional fillers are needed to improve the mechanical and thermal properties of the resins; zirconia is one such filler. However, it has been reported that aggregation may occur in the epoxy composites as the amount of zirconia increases, preventing enhancement of the mechanical strength of the epoxy composites. Herein, to reduce the aggregation, zirconia was well dispersed on halloysite nanotubes (HNTs), which have high thermal and mechanical strength, by a conventional wet impregnation method. The HNTs were impregnated with zirconia at different loadings using zirconyl chloride octahydrate as a precursor. The mechanical and thermal strengths of the epoxy composites with these fillers were investigated. The zirconia-impregnated HNTs (Zr/HNT) were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and tunneling electron microscopy (TEM). The hardening conditions of the epoxy composites were analyzed by differential scanning calorimetry (DSC). The thermal strength of the epoxy composites was studied by thermomechanical analysis (TMA) and micro-calorimetry and the mechanical strength of the epoxy composites (flexural strength and tensile strength) was studied by using a universal testing machine (UTM). The mechanical and thermal strengths of the epoxy composites with Zr/HNT were improved compared to those of the epoxy composite with HNT, and also increased as the zirconia loading on HNT increased.

Synthesis of Benzene Tetracarboxamide Polyamine and Its Effect on Epoxy Resin Properties.

Epoxy resins have found various industrial applications in high-performance thermosetting resins, high-performance composites, electronic-packaging materials, adhesives, protective coatings, etc., due to their outstanding performance, including high toughness, high-temperature performance, chemical and environmental resistance, versatile processability and adhesive properties. However, cured epoxy resins are very brittle, which limits their applications. In this work, we attempted to enhance the toughness of cured epoxy resins by introducing benzene tetracarboxamide polyamine (BTCP), synthesized from pyromellitic dianhydride (PMDA) and diamines in N-methyl-2-pyrrolidone (NMP) solvent. During this reaction, increased viscosity and formation of amic acid could be confirmed. The chemical reactions were monitored and evidenced using ¹H-NMR spectroscopy, FT-IR spectroscopy, water gel-phase chromatography (GPC) analysis, amine value determination and acid value determination. We also studied the effect of additives on thermomechanical properties using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamical mechanical analysis (DMA), thermomechanical analysis (TMA) and by measuring mechanical properties. The BTCP-containing epoxy resin exhibited high mechanical strength and adhesion strength proportional to the amount of BTCP. Furthermore, field-emission scanning electron microscopy images were obtained for examining the cross-sectional morphology changes of the epoxy resin specimens with varying amounts of BTCP.

Control of silica-zirconia nanoparticles for uniform porous SiO2-ZrO2 membranes.

Silica-zirconia composite sols were prepared by means of a sol-gel method, using tetraethylorthosilicate (TEOS) and zirconium tetra-n-butoxide (ZrTB) precursors. TEOS, ZrTB, HCl, H2O and EtOH were mixed at 70 degrees C for 24 hours to give molar ratios of 1:1:8-80:0.2-1.0:100-300. The mean particle size of the silica-zirconia sol was controlled by the concentration of the alkoxides and catalyst, as well as the water molar ratio in the starting solution. The particle size of the SiO2-ZrO2 sol, which was analyzed by dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM), was in the range of 20 to 350 nm. The SiO2-ZrO2 sol solutions of different sol sizes were coated onto porous stainless steel supports (O.D. 10 mm, length: 20 mm, 316L SUS, Mott corp. USA) by a dipping-rolling-freezing-fast drying (DRFF) and soaking-rolling-freezing-fast drying (SRFF) method. After coating with SiO2-ZrO2 sol, the single gas permeation characteristics (He, H2 and N2) of the resulting SiO2-ZrO2 membranes were evaluated at room temperature. This produced a decrease in the mean flow diameter and H2/N2 permselectivity in the range of 2.0-3.5. Finally, following the results of gas permeation testing, the pore size of the membranes was controlled by changing their particle size.