Search Results (61)

This paper presents a comprehensive investigation into the synthesis, morphological characteristics, electrical conductivity, dielectric behavior, and electrocatalytic activity of perovskite-structured iron manganite (FeMnO₃), with a specific focus on its performance in the hydrogen evolution reaction (HER). FeMnO₃(FMO) nanoparticles (NPs) were synthesized using a sol–gel-type Pechini method and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and field-emission scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (FESEM-EDS). XRD analysis confirmed the formation of a crystalline structure with cubic symmetry assigned to the Ia-3 space group, with an average crystallite size of 52.47 nm. FESEM images revealed a relatively uniform morphology with an average particle diameter of 55.84 nm. The redox and oxidation states of Fe and Mn can be studied by temperature-programmed oxidation (TPO-O₂) in order to understand oxygen uptake and metal oxidation processes occurring within the FMO lattice. The dielectric constant, dielectric loss, electric modulus and electrical conductivity were calculated as a function of frequency and temperature using a Novocontrol Alpha-A broadband dielectric spectrometer (Novocontrol system) coupled with the LCR-800 precision meter. The dielectric data reveal that the FMO has semiconducting behavior with dominant charge- or ionic-relaxation processes. The electrocatalytic activity toward the HER was evaluated using linear sweep voltammetry (LSV), with the working electrode modified by an FMO catalyst ink. The material exhibited significant catalytic activity within the HER potential range, and an increase in the number of cycles led to stabilized current and enhanced hydrogen evolution. These results highlight the stability of FeMnO₃ for hydrogen generation. Full article

Water electrolysis using electricity generated from renewable sources is a promising approach for producing green hydrogen. However, this process requires the development of electrocatalysts that are not only highly active and durable but also low-cost. Considerable efforts are being directed toward discovering and optimizing such materials, and this study contributes to the ongoing research in this area. In this work, three novel LaMnO₃ perovskite–graphene oxide hybrids—namely LaMnO₃/GO, Ag-doped LaMnO₃/GO, and Pd-doped LaMnO₃/GO—were synthesized and investigated for their electrocatalytic activity in water electrolysis under strongly alkaline conditions. To the best of our knowledge, these hybrid materials have not been previously reported in the context of electrocatalytic water splitting. Among the electrodes fabricated and tested for the hydrogen evolution reaction (HER), the one based on a catalyst ink containing Pd-doped LaMnO₃/GO mixed with carbon black showed the best performance, achieving a low overpotential of 0.385 V at a current density of −10 mA/cm². It also demonstrated good stability in the alkaline electrolyte and exhibited a Tafel slope of 0.34 V. These findings highlight the potential of the studied materials as effective and previously unreported electrocatalysts for water splitting. Full article

Advanced ceramics are known for their lightweight, high-temperature resistance, corrosion resistance, and biocompatibility. They are crucial in energy conversion, environmental protection, and aerospace fields. This review highlights the recent advancements in ceramic matrix composites, high-entropy ceramics, and polymer-derived ceramics, alongside various fabrication techniques such as three-dimensional printing, advanced sintering, and electric-field-assisted joining. Beyond the fabrication process, we emphasize how different processing methods impact microstructure, transport properties, and performance metrics relevant to catalysis. Additive manufacturing routes, such as direct ink writing, digital light processing, and binder jetting, are discussed and normalized based on factors such as relative density, grain size, pore architecture, and shrinkage. Cold and flash sintering methods are also examined, focusing on grain-boundary chemistry, dopant compatibility, and scalability for catalyst supports. Additionally, polymer-derived ceramics (SiOC, SiCN, SiBCN) are reviewed in terms of their catalytic performance in hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and CO₂ reduction reaction. CeO₂-ZrO₂ composites are particularly highlighted for their use in environmental catalysis and high-temperature gas sensing. Furthermore, insights on the future industrialization, cross-disciplinary integration, and performance improvements in catalytic applications are provided. Full article

The reproducibility of oxygen reduction reaction (ORR) activity assessment for platinum-based electrocatalysts using the rotating disk electrode (RDE) method is critically dependent on the quality of the fabricated catalytic layer. This work presents a comprehensive study on optimizing catalytic ink formulation—specifically the water-to-isopropanol (H₂O:IPA) solvent ratio and the ionomer-to-carbon (I/C) ratio—to achieve a homogeneous catalytic layer and ensure high data reproducibility for monometallic Pt/C and bimetallic PtCu/C catalysts. A key aspect of this research is the implementation of a simple and effective visual inspection method using a benchtop digital microscope to rapidly assess catalytic layer quality, which was shown to correlate directly with electrochemical performance. The optimal ink composition was found to be catalyst-specific. For Pt/C, the highest mass activity of 353 A/g~Pt~ was achieved with a solvent ratio of 1:3 (H₂O:IPA) and an I/C ratio of 0.3. For PtCu/C, the best performance was obtained with the same solvent ratio (1:3) but a higher I/C ratio of 0.4, yielding a mass activity of 491 A/g~Pt~. It was demonstrated that ink compositions leading to layer inhomogeneities, such as aggregates and “coffee-ring” effects, significantly impair mass transport and lead to underestimated ORR activity. The study underscores the absence of a universal ink recipe and establishes that the optimization of ink parameters for each specific catalyst is essential for obtaining reliable and reproducible electrochemical data. Full article

The dehydrogenation of cyclohexane is of vital importance for the production of Nylon-6 and Nylon-66, as it enhances atom utilization efficiency. Ca-doped platinum catalysts have been employed in alkane dehydrogenation due to their ability to selectively activate C–H bonds while minimizing C–C bond cleavage. However, owing to their limited selectivity toward cyclohexene, Pt-Ca/Al₂O₃ catalysts have not been widely adopted in the field of partial dehydrogenation to alkenes. In this work, Al₂O₃ supports are fabricated using the direct ink writing (DIW) 3D printing technique, incorporating designed channels. After impregnation and calcination at 550 °C, the distribution of active species, surface acidity, and basicity are optimized, resulting in a cyclohexene yield of 8.9%. The cyclohexene yield and stability of the 3D-printed catalysts are significantly higher than those of the granular catalyst, attributed to enhanced heat and mass transfer performance facilitated by the internal channels. Full article

Anion-exchange membranes (AEMs) not only enable the fabrication of catalyst-coated membranes without precious metals but are also projected to achieve a technology-readiness level (TRL) suitable for industrial deployment before the end of this decade. Accurate and reproducible water uptake data are essential for guiding AEM design, yet conventional gravimetric methods—relying on manual blotting and loosely defined drying steps—can introduce variabilities exceeding 20%. Here, we present a standardized protocol that transforms water uptake measurements from rough estimates into precise, comparable “hydration fingerprints.” By replacing manual wiping with a calibrated pressure-blotting rig (0.44 N cm⁻² for 10 s twice) and verifying both dry and wet states via ATR-FTIR spectroscopy, we dramatically reduce scatter and align our FAAM-PK-75 (Fumatech, Bietigheim, Germany) results with published benchmarks in DI water, aqueous KOH (0.1–9 M), various alcohols, and controlled humidity (39–96% RH). These uptake profiles reveal how OH⁻ screening, thermal densification at 60 °C, and PEEK reinforcement govern equilibrium hydration. A low-cost salt-bath method for vapor-phase sorption further distinguishes reinforced from unreinforced architectures. Extending the workflow to additional commercial and custom membranes confirms its broad applicability. Ultimately, this work establishes a new benchmark for AEM hydration testing and provides a predictive toolkit for correlating water content with conductivity, dimensional stability, and membrane–ink interactions during catalyst-coated membrane fabrication. Full article

Hydrogen generation has become a popular research subject in light of currently pressing issues, such as the rapidly increasing environmental pollution, the depleting fossil fuel reserves, and the looming energy crisis. Sustainable electrochemical water splitting is regarded as one of the most desirable methods for obtaining green hydrogen. Considering this state of affairs, the water splitting electrocatalytic activity of glassy carbon electrodes modified with birnessite-type K₂Mn₄O₈ and mixed-valence iron phosphate Fe₃(PO₃OH)₄(H₂O)₄ materials were evaluated in electrolyte solutions having different pH values. Both compounds were characterized by X-ray diffraction and FT-IR spectroscopy in order to analyze their phase purity and their structural features. The most catalytically active birnessite-type K₂Mn₄O₈-based electrode was manufactured using a catalyst ink containing only the electrocatalyst dispersed in ethanol and Nafion solution. In 0.1 M H₂SO₄, it exhibited an oxygen evolution reaction (OER) overpotential of 1.07 V and a hydrogen evolution reaction (HER) overpotential of 0.957 V. The Tafel slopes obtained in the OER and HER experiments were 0.180 and 0.142 V/dec, respectively. The most catalytically active mixed-valence iron phosphate Fe₃(PO₃OH)₄(H₂O)₄-based electrode was obtained with a catalyst ink containing the specified material mixed with carbon black and dispersed in ethanol and Nafion solution. In a strongly alkaline medium, it displayed a HER overpotential of 0.515 V and a Tafel slope value of 0.122 V/dec. The two electrocatalysts have not been previously investigated in this way, and the acquired data provide insights into their electrocatalytic activity and improve the scientific understanding of their properties and applicative potential. Full article

This study examines the effects of several commercial surfactants on the dispersion of catalyst inks for proton exchange membrane fuel cells (PEMFCs). Catalyst inks containing Pt/C were spray-coated and assembled into membrane electrode assemblies (MEAs) by hot pressing. The structural and electrochemical properties of the resulting catalyst layers were characterized through particle size analysis, zeta potential measurements, contact angle determinations, and single-cell performance tests. Among the formulations evaluated, the ink with non-ionic surfactant Triton X-100 (TX) delivered the best performance, achieving a current density of 1134 mA/cm² at 0.3 V—substantially higher than that of the surfactant-free control. These findings provide practical guidance for selecting appropriate surfactants to optimize catalyst-ink preparation and enhance PEMFC performance. Full article

A group of renewable, unsaturated resins from itaconic acid, 1,8-octanediol, and succinic anhydride were synthesized in a non-solvent and non-catalyst melt polycondensation reaction. The study addresses the need for sustainable polymeric materials suitable for additive manufacturing by investigating the influence of synthesis parameters—namely itaconic acid content, reaction time, and temperature—on the properties of poly(octamethylene itaconate-co-succinate) (POItcSc). The Box-Behnken mathematical planning method was applied to optimize the reaction conditions. The optimal synthesis conditions of POItcSc were achieved with an itaconic acid molar fraction = 0.50:0.50, reaction time t = 7 h, and reaction temperature T = 150 °C. The conversion of the carboxyl group (by titration) was 83.3%, and the maintenance of C=C bonds (by NMR) was 88.7%. Structural characterization confirmed the formation of the desired polymer through FTIR and ¹H NMR analyses. Molecular weight (M_n = 1001 g/mol for an optimal product), thermal behavior (DSC, TG, DTG), and rheological properties (η = 14.4 and 3.6 Pa∙s for an optimal product at 25 and 36.6 °C) were systematically evaluated. The synthesized POItcSc resins were transparent and exhibited physicochemical properties favorable for extrusion-based 3D printing techniques such as Direct Ink Writing, offering a promising alternative to conventional petrochemical-based inks. Full article

The current environmental pollution and energy crises are global concerns that must be addressed. Considering this background, three perovskites (YMnO₃, Co-doped YMnO₃, and Sn-doped YMnO₃) were synthesized via a sol–gel method and characterized by XRD, SEM, and EDX. Their water-splitting electrocatalytic activity was evaluated in a strongly alkaline medium. The highest activity was observed during hydrogen evolution reaction (HER) experiments on a glassy carbon electrode coated with a catalyst ink containing the Co-doped material. Initially, the HER overpotential value at −10 mA/cm² was 0.59 V, and the Tafel slope was 115 mV/dec. Following a chronoamperometric stability test, the overpotential became 0.46 V and the Tafel slope 119 mV/dec. The higher HER activity of the modified electrode is ascribed to a higher number of catalytic sites exposed to the electrolyte solution and the presence of Carbon Black. The photocatalytic activity of the perovskites was investigated as well, using different experimental conditions and simulated solar irradiation. The results show that the photocatalytic activity can be improved by doping, and the highest removal efficiency is achieved in the presence of the Co-doped YMnO₃ when ~60% of 17α-ethynylestradiol is degraded. Furthermore, the initial pH has no favorable effect on the degradation efficiency. The reusability of Co-doped YMnO₃ was also tested and minimal activity loss was found after three photocatalytic cycles. Full article

Accurately determining the Hansen solubility parameters (HSPs) of fuel cell ionomers is crucial for optimizing the dispersion and dispersive state of the ionomer in fuel cell catalyst inks. This directly impacts the structure and coating process of the catalyst layer in proton exchange membrane fuel cells (PEMFCs). The Hansen solubility parameters (HSPs) of the Nafion ionomer were calculated by the Hansen solubility parameter software (HSPiP), inverse gas chromatography (IGC), and group contribution methods. The applicability and accuracy of the different algorithms are discussed. It was found that the solubility parameters (SPs) measured by the HSPiP method were higher, while the SPs measured by the IGC and group contribution methods were lower. However, for the ionomer with both a hydrophobic backbone and hydrophilic side chain, the HSPiP method offered a more reasonable HSP determination method. The dual HSPs of Nafion calculated by the HSPiP method were found to be δ_d = 16.4 MPa^1/2 (dispersion force), δ_p = 10.5 MPa^1/2 (polar interaction), and δ_h = 8.9 MPa^1/2 (hydrogen bonding) for the hydrophobic backbone and δ_d = 15.2 MPa^1/2, δ_p = 11.7 MPa^1/2, and δ_h = 15.9 MPa^1/2 for the hydrophilic side chain. These results provide a thermodynamic basis for solvent design in fuel cell catalyst-layer fabrication. Full article

Proton Exchange Membrane Fuel Cells (PEMFCs) are widely regarded as promising clean energy technologies due to their high energy conversion efficiency, low environmental impact, and versatile application potential in transportation, stationary power, and portable devices. Central to the operation and performance of PEMFCs are advancements in materials and manufacturing processes that directly influence their efficiency, durability, and scalability. This review provides a comprehensive overview of recent progress in these areas, emphasizing the critical role of membrane electrode assembly (MEA) technology and its constituent components, including catalyst layers, membranes, and gas diffusion layers (GDLs). The MEA, as the heart of PEMFCs, has seen significant innovations in its structure and manufacturing methodologies to ensure optimal performance and durability. At the material level, catalyst layer advancements, including the development of platinum-group metal catalysts and cost-effective non-precious alternatives, have focused on improving catalytic activity, durability, and mass transport. Similarly, the evolution of membranes, particularly advancements in perfluorosulfonic acid membranes and alternative hydrocarbon-based or composite materials, has addressed challenges related to proton conductivity, mechanical stability, and operation under harsh conditions such as low humidity or high temperature. Additionally, innovations in gas diffusion layers have optimized their porosity, hydrophobicity, and structural properties, ensuring efficient reactant and product transport within the cell. By examining these interrelated aspects of PEMFC development, this review aims to provide a holistic understanding of the state of the art in PEMFC materials and manufacturing technologies, offering insights for future research and the practical implementation of high-performance fuel cells. Full article

This study delves into the distinctive selective property exhibited by a non-conjugated cholesterol-based polymer, poly(CEM₁₁-b-EHA₇), in sorting semiconducting single-walled carbon nanotubes (s-SWCNTs) within isooctane. Comprised of 11 repeating units of cholesteryloxycarbonyl-2-hydroxy methacrylate (CEM) and 7 repeating units of 2-ethylhexyl acrylate (EHA), this non-conjugated polymer demonstrates robust supramolecular interactions across the sp² surface structure of carbon nanotubes and graphene. When coupled with the Double Liquid-Phase Extraction (DLPE) technology, the polymer effectively segregates s-SWCNTs into the isooctane phase (nonpolar) while excluding metallic SWCNTs (m-SWCNTs) in the water phase (polar). DLPE proves particularly efficient in partitioning larger-diameter s-SWCNTs (0.85–1.0 nm) compared to those dispersed directly in isooctane by poly(CEM₁₁-b-EHA₇) using direct liquid-phase exfoliation (LPE) techniques for diameters ranging from 0.75 to 0.95 nm. The DLPE method, bolstered by poly(CEM₁₁-b-EHA₇), successfully eliminates impurities from s-SWCNT extraction, including residual metallic catalysts and carbonaceous substances, which constitute up to 20% of raw HiPCO SWCNTs. DLPE emerges as a scalable and straightforward approach for selectively extracting s-SWCNTs in nonpolar, low-boiling-point solvents like alkanes. These dispersions hold promise for fabricating fast-drying s-SWCNT inks, which are ideal for printed and flexible thin-film transistors. Full article

At present, there are too few organ and tissue donors. Due to the needs of the medical market, scientists are seeking new solutions. Those can be found in tissue engineering by synthesizing synthetic cell scaffolds. We have decided to synthesize a potential UV-crosslinked bio-ink for 3D printing, poly(1,4-butanediol itaconate), in response to emerging needs. Diol polyesters are commonly investigated for their use in tissue engineering. However, itaconic acid makes it possible to post-modify the obtained polymer via UV-crosslinking. This work aims to optimize the synthesis of poly(1,4-butanediol itaconate) in the presence of a catalyst, zinc acetate, without using any toxic reactant. The experiments used itaconic acid and 1,4-butanediol using the Box–Behnken mathematical planning method. The input variables were the amount of the catalyst used, as well as the time and temperature of the synthesis. The optimized output variables were the percentage conversion of carboxyl groups, the percentage of unreacted C=C bonds, and the product’s visual and viscosity analysis. The significance of the varying synthesis parameters was determined in each statistical model. The optimum conditions were as follows: amount of catalyst 0.3%_nCOOH, reaction time 4 h, and temperature 150 °C. The temperature had the most significant impact on the product characteristics, mainly due to side reactions. Experimentally developed models of the polymerization process enable the effective synthesis of a polymer “tailor-made” for a specific application. Full article

In the context of water electrolysis being highlighted as a promising technology for the large-scale sustainable production of hydrogen, the water-splitting electrocatalytic properties of an asymmetrically functionalized A₃B zinc metalated porphyrin, namely, Zn(II) 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin, were evaluated in a wide pH range. Two different electrode manufacturing procedures were employed to outline the porphyrin’s applicative potential for the O₂ and H₂ evolution reactions (OER and HER). The electrode, manufactured by coating the catalyst on a graphite support from a dimethylsulfoxide solution, displayed electrocatalytic activity for the OER in an acidic electrolyte. An overpotential value of 0.44 V (at i = 10 mA/cm²) and a Tafel slope of 0.135 V/dec were obtained. The modified electrode that resulted from applying a Zn(II)-porphyrin-containing catalyst ink onto the same substrate type was identified as a bifunctional water-splitting catalyst in a neutral medium. OER and HER overpotentials of 0.78 and 1.02 V and Tafel slopes of 0.39 and 0.249 V/dec were determined. This is the first Zn(II)-porphyrin to be reported as a heterogenous bifunctional water-splitting electrocatalyst in neutral aqueous electrolyte solution and is one of very few porphyrins behaving as such. The TEM analysis of the porphyrin’s self-assembly behavior revealed a wide variety of architectures. Full article