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Keywords = porous mixed oxides

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17 pages, 3389 KiB  
Article
Enhanced OH Transport Properties of Bio-Based Anion-Exchange Membranes for Different Applications
by Suer Kurklu-Kocaoglu, Daniela Ramírez-Espinosa and Clara Casado-Coterillo
Membranes 2025, 15(8), 229; https://doi.org/10.3390/membranes15080229 - 31 Jul 2025
Viewed by 371
Abstract
The demand for anion exchange membranes (AEMs) is growing due to their applications in water electrolysis, CO2 reduction conversion and fuel cells, as well as water treatment, driven by the increasing energy demand and the need for a sustainable future. However, current [...] Read more.
The demand for anion exchange membranes (AEMs) is growing due to their applications in water electrolysis, CO2 reduction conversion and fuel cells, as well as water treatment, driven by the increasing energy demand and the need for a sustainable future. However, current AEMs still face challenges, such as insufficient permeability and stability in strongly acidic or alkaline media, which limit their durability and the sustainability of membrane fabrication. In this study, polyvinyl alcohol (PVA) and chitosan (CS) biopolymers are selected for membrane preparation. Zinc oxide (ZnO) and porous organic polymer (POP) nanoparticles are also introduced within the PVA-CS polymer blends to make mixed-matrix membranes (MMMs) with increased OH transport sites. The membranes are characterized based on typical properties for AEM applications, such as thickness, water uptake, KOH uptake, Cl and OH permeability and ion exchange capacity (IEC). The OH transport of the PVA-CS blend is increased by at least 94.2% compared with commercial membranes. The incorporation of non-porous ZnO and porous POP nanoparticles into the polymer blend does not compromise the OH transport properties. On the contrary, ZnO nanoparticles enhance the membrane’s water retention capacity, provide basic surface sites that facilitate hydroxide ion conduction and reinforce the mechanical and thermal stability. In parallel, POPs introduce a highly porous architecture that increases the internal surface area and promotes the formation of continuous hydrated pathways, essential to efficient OH mobility. Furthermore, the presence of POPs also contributes to reinforcing the mechanical integrity of the membrane. Thus, PVA-CS bio-based membranes are a promising alternative to conventional ion exchange membranes for various applications. Full article
(This article belongs to the Special Issue Membrane Technologies for Water Purification)
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16 pages, 3885 KiB  
Article
Synthesis and Properties of Bi1.8Mn0.5Ni0.5Ta2O9-Δ Pyrochlore
by Sergey V. Nekipelov, Olga V. Petrova, Alexandra V. Koroleva, Mariya G. Krzhizhanovskaya, Kristina N. Parshukova, Nikolay A. Sekushin, Boris A. Makeev and Nadezhda A. Zhuk
Chemistry 2025, 7(4), 119; https://doi.org/10.3390/chemistry7040119 - 25 Jul 2025
Viewed by 180
Abstract
Pyrochlore Bi1.8Mn0.5Ni0.5Ta2O9-Δ (sp.gr. Fd-3m, a = 10.5038(9) Å) was synthesized by the solid-phase reaction method and characterized by vibrational and X-ray spectroscopy. According to scanning electron microscopy, the ceramics are characterized by a [...] Read more.
Pyrochlore Bi1.8Mn0.5Ni0.5Ta2O9-Δ (sp.gr. Fd-3m, a = 10.5038(9) Å) was synthesized by the solid-phase reaction method and characterized by vibrational and X-ray spectroscopy. According to scanning electron microscopy, the ceramics are characterized by a porous microstructure formed by randomly oriented oblong grains. The average crystallite size determined by X-ray diffraction is 65 nm. The charge state of transition element cations in the pyrochlore was analyzed by soft X-ray spectroscopy using synchrotron radiation. For mixed pyrochlore, a characteristic shift of Bi4f and Ta4f and Ta5p spectra to the region of lower energies by 0.25 and 0.90 eV is observed compared to the binding energy in Bi2O3 and Ta2O5 oxides. XPS Mn2p spectrum of pyrochlore has an intermediate energy position compared to the binding energy in MnO and Mn2O3, which indicates a mixed charge state of manganese (II, III) cations. Judging by the nature of the Ni2p spectrum of the complex oxide, nickel ions are in the charge state of +(2+ζ). The relative permittivity of the sample in a wide temperature (up to 350 °C) and frequency range (25–106 Hz) does not depend on the frequency and exhibits a constant low value of 25. The minimum value of 4 × 10−3 dielectric loss tangent is exhibited by the sample at a frequency of 106 Hz. The activation energy of conductivity is 0.7 eV. The electrical behavior of the sample is modeled by an equivalent circuit containing a Warburg diffusion element. Full article
(This article belongs to the Section Inorganic and Solid State Chemistry)
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17 pages, 5437 KiB  
Article
Characterization of Different Types of Screen-Printed Carbon Electrodes Modified Electrochemically by Ceria Coatings
by Reni Andreeva, Aleksandar Tsanev, Georgi Avdeev and Dimitar Stoychev
Metals 2025, 15(7), 741; https://doi.org/10.3390/met15070741 - 30 Jun 2025
Viewed by 226
Abstract
Electrochemical formation of ceria (mixed Ce2O3 and CeO2) coatings on different types of screen-printed carbon electrodes (SPCEs) (based on graphite (C110), carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), carbon nanofibers (CNF), and mesoporous carbon (MC)) were studied. Their [...] Read more.
Electrochemical formation of ceria (mixed Ce2O3 and CeO2) coatings on different types of screen-printed carbon electrodes (SPCEs) (based on graphite (C110), carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), carbon nanofibers (CNF), and mesoporous carbon (MC)) were studied. Their potential applications as catalysts for various redox reactions and electrochemical sensors were investigated. The ceria oxide layers were electrodeposited on SPCEs at various current densities and deposition time. The morphology, structure, and chemical composition in the bulk of the ceria layers were studied by SEM and EDS methods. XRD was used to identify the formed phases. The concentration, chemical composition and chemical state of the elements on the surface of studied samples were characterized by XPS. It was established that the increase of the concentration of CeCl3 in the solution and the cathode current density strongly affected the surface structure and concentration (relation between Ce3+ and Ce4+, respectively) in the formed ceria layers. At low concentration of CeCl3 (0.1M) and low values of cathode current density (0.5 mA·cm−2), porous samples were obtained, while with their increase, the ceria coatings grew denser. Full article
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18 pages, 3756 KiB  
Article
Advanced Electrochromic Functionality via Layered Cobalt Oxide Deposition on Tungsten Oxide Electrodes
by Pritam J. Morankar, Rutuja U. Amate, Mrunal K. Bhosale, Namita A. Ahir and Chan-Wook Jeon
Coatings 2025, 15(4), 403; https://doi.org/10.3390/coatings15040403 - 28 Mar 2025
Cited by 1 | Viewed by 415
Abstract
The integration of various transition metal oxides into tungsten oxide (WO3) has been widely investigated to enhance its electrochromic (EC) performance. This approach aims to address the inherent limitations of individual metal oxides, such as poor durability, inadequate color neutrality, and [...] Read more.
The integration of various transition metal oxides into tungsten oxide (WO3) has been widely investigated to enhance its electrochromic (EC) performance. This approach aims to address the inherent limitations of individual metal oxides, such as poor durability, inadequate color neutrality, and restricted coloring efficiency and optical properties. The use of mixed metal oxides has emerged as a promising strategy, enabling a synergistic effect that optimizes EC performance and expands the material’s functional capabilities. In this study, we compare single-layer WO3 films with bilayer WO3/cobalt oxide (CoO) (denoted as W@C) composite films, focusing on their structural, morphological, and electrochromic properties. Both films were fabricated using the electrodeposition technique, with a consistent number of deposition cycles. Field emission scanning electron microscopy (FESEM) analysis revealed that the WO3 film presented a tightly packed arrangement of nanogranules. In contrast, the bilayer W@C composite thin film exhibited a highly interconnected and porous granular structure, with morphology evolving into larger spherical aggregates. The optimized bilayer W@C composite demonstrated exceptional electrochromic performance, achieving an optical modulation of 85.0% at 600 nm and a significantly improved coloration efficiency of 96.07 cm2/C. Stability tests confirmed its remarkable durability, showing only a 1.05% decrease in optical contrast after 5000 s of operation. Additionally, a prototype electrochromic device based on the W@C film demonstrated an optical modulation of 52.13% and outstanding long-term stability, with minimal degradation in performance. Full article
(This article belongs to the Special Issue Thermoelectric Thin Films for Thermal Energy Harvesting)
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15 pages, 2932 KiB  
Article
Microstructural and Magnetic Properties of Polyamide-Based Recycled Composites with Iron Oxide Nanoparticles
by Lucas G. Dos Santos, Daina D. A. Buelvas, Daniel F. Valezi, Bruno L. S. Vicentin, Christian M. M. Rocha, Eduardo Di Mauro and Felipe de A. La Porta
Magnetism 2025, 5(1), 5; https://doi.org/10.3390/magnetism5010005 - 25 Feb 2025
Cited by 2 | Viewed by 1897
Abstract
This study explores a sustainable approach to developing magnetic nanocomposites by synthesizing a mixed-phase iron oxide (IO) and recycled polyamide (RPA) composite from textile waste. The RPA/IO nanocomposite’s microstructural and magnetic properties were characterized using X-ray diffraction (XRD) with Rietveld refinement, scanning, transmission [...] Read more.
This study explores a sustainable approach to developing magnetic nanocomposites by synthesizing a mixed-phase iron oxide (IO) and recycled polyamide (RPA) composite from textile waste. The RPA/IO nanocomposite’s microstructural and magnetic properties were characterized using X-ray diffraction (XRD) with Rietveld refinement, scanning, transmission electron microscopy (SEM, TEM), and vibrating sample magnetometry (VSM). The proportions of the Fe3O4 and γ-Fe2O3 phases were found to be 23.2 wt% and 76.8 wt%, respectively. SEM and TEM showed a porous, agglomerated IO surface morphology with an average particle size of 14 nm. Magnetic analysis revealed ferrimagnetic and superparamagnetic behavior, with VSM showing saturation magnetization values of 21.81 emu g−1 at 5 K and 18.84 emu g−1 at 300 K. Anisotropy constants were estimated at 4.28 × 105 and 1.53 × 105, respectively, for IO and the composite, with a blocking temperature of approximately 178 K at 300 K. These results contribute to understanding the magnetic behavior of IO and their nanocomposites, which is crucial for their potential applications in emerging technologies. Full article
(This article belongs to the Special Issue Magnetism and Correlations in Nanomaterials)
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14 pages, 3217 KiB  
Article
α-Al2O3 Functionalized with Lithium Ions Especially Useful as Inert Catalyst Bed Supports
by Mirjana Stamenić, Timotei Bogdan Bacoș, Aleksandar Milivojević, Vuk Adžić, Mihaela Ciopec, Nicoleta Sorina Nemeş, Adina Negrea and Adrian Eugen Cioablă
Molecules 2025, 30(3), 577; https://doi.org/10.3390/molecules30030577 - 27 Jan 2025
Cited by 1 | Viewed by 745
Abstract
The alumina, in the form of α-Al2O3 tabular balls, considered in this study is a high-purity form of aluminum oxide that has been fired at high temperatures (well above 1900 °C), virtually removing porosity. However, the purity and inertness of [...] Read more.
The alumina, in the form of α-Al2O3 tabular balls, considered in this study is a high-purity form of aluminum oxide that has been fired at high temperatures (well above 1900 °C), virtually removing porosity. However, the purity and inertness of the surface of the Al2O3 tabular balls minimize the catalytic activity, which is why lithium doping was tried. Thus, the target of this study was the effect of doping with lithium ions in some tabular balls of Al2O3 (the crystalline structure is corundum) on the improvement of the catalytic properties of alumina. This study examined the impact of a lithium catalyst on the combustion of various fuels within a porous inert medium (PIM) burner. This study specifically compared low calorific gaseous fuel (e.g., biogas) combustion in a PIM burner with and without the lithium catalyst. The experimental setup comprised a gas preparation unit for mixing CNG and CO2 to simulate biogas and a PIM burner. The PIM burner comprised Al2O3 spheres (13 mm diameter, 45% porosity) in a random packing configuration. Three fuels, varying in composition and lower heating value (LHV ranging from 20.771 to 27.695 MJ/m3), were combusted at air ratios ranging from 1.67 to 1.79. The results indicated that the catalyst increased peak combustion temperatures by 23.2 °C to 51.4 °C, depending on the fuel type and air ratio. Significantly higher carbon monoxide (CO) concentrations were observed without the catalyst, particularly with fuel type F1, while nitrous oxide (NOx) levels remained consistently low. Upstream flame propagation was observed in the presence of the catalyst. These findings demonstrate the potential of lithium catalysts to enhance combustion stability and reduce emissions in porous media combustion burners. Following these studies, it can be stated that Li(I) has the role of promoter of the catalytic process. Full article
(This article belongs to the Section Materials Chemistry)
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20 pages, 6075 KiB  
Article
Photocatalysis by Mixed Oxides Containing Niobium, Vanadium, Silica, or Tin
by Agnieszka Feliczak-Guzik, Agata Wawrzyńczak and Izabela Nowak
Catalysts 2025, 15(2), 118; https://doi.org/10.3390/catal15020118 - 26 Jan 2025
Viewed by 826
Abstract
Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with [...] Read more.
Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10−4 mol/dm3) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material. Full article
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20 pages, 10254 KiB  
Article
Discernible Orientation for Tortuosity During Oxidative Precipitation of Fe(II) in Porous Media: Laboratory Experiment and Micro-CT Imaging
by Wenran Cao, Ekaterina Strounina, Harald Hofmann and Alexander Scheuermann
Minerals 2025, 15(1), 91; https://doi.org/10.3390/min15010091 - 19 Jan 2025
Cited by 1 | Viewed by 1275
Abstract
In the mixing zone, where submarine groundwater carrying ferrous iron [Fe(II)] meets seawater with dissolved oxygen (DO), the oxidative precipitation of Fe(II) occurs at the pore scale (nm~μm), and the resulting Fe precipitation significantly influences the seepage properties at the Darcy scale (cm~m). [...] Read more.
In the mixing zone, where submarine groundwater carrying ferrous iron [Fe(II)] meets seawater with dissolved oxygen (DO), the oxidative precipitation of Fe(II) occurs at the pore scale (nm~μm), and the resulting Fe precipitation significantly influences the seepage properties at the Darcy scale (cm~m). Previous studies have presented a challenge in upscaling fluid dynamics from a small scale to a large scale, thereby constraining our understanding of the spatiotemporal variations in flow paths as porous media evolve. To address this limitation, this study simulated subsurface mixing by injecting Fe(II)-rich freshwater into a DO-rich saltwater flow within a custom-designed syringe packed with glass beads. Micro-computed tomography imaging at the representative elementary volume scale was utilized to track the development of Fe precipitates over time and space. Experimental observations revealed three distinct stages of Fe hydroxides and their effects on the flow dynamics. Initially, hydrous Fe precipitates were characterized by a low density and exhibited mobility, allowing temporarily clogged pathways to intermittently reopen. As precipitation progressed, the Fe precipitates accumulated, forming interparticle bonding structures that redirected the flow to bypass clogged pores and facilitated precipitate flushing near the syringe wall. In the final stage, a notable reduction in the macroscopic capillary number from 3.0 to 0.05 indicated a transition from a viscous- to capillary-dominated flow, which led to the construction of ramified, tortuous flow channels. This study highlights the critical role of high-resolution imaging techniques in bridging the gap between pore-scale and continuum-scale analyses of multiphase flows in hydrogeochemical processes, offering valuable insights into the complex groundwater–seawater mixing. Full article
(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)
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15 pages, 5276 KiB  
Article
ZIF-8-Embedded Cation-Exchange Membranes with Improved Monovalent Ion Selectivity for Capacitive Deionization
by Eui-Gyu Han, Ji-Hyeon Lee and Moon-Sung Kang
Membranes 2025, 15(1), 19; https://doi.org/10.3390/membranes15010019 - 9 Jan 2025
Cited by 1 | Viewed by 1681
Abstract
Membrane capacitive deionization (MCDI) is an electrochemical ion separation process that combines ion-exchange membranes (IEMs) with porous carbon electrodes to enhance desalination efficiency and address the limitations of conventional capacitive deionization (CDI). In this study, a cation-exchange membrane (CEM) embedded with a metal–organic [...] Read more.
Membrane capacitive deionization (MCDI) is an electrochemical ion separation process that combines ion-exchange membranes (IEMs) with porous carbon electrodes to enhance desalination efficiency and address the limitations of conventional capacitive deionization (CDI). In this study, a cation-exchange membrane (CEM) embedded with a metal–organic framework (MOF) was developed to effectively separate monovalent and multivalent cations in influent solutions via MCDI. To fabricate CEMs with high monovalent ion selectivity, ZIF-8 was incorporated into sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) at various weight ratios. The resulting membranes were systematically characterized using diverse electrochemical methods. The ZIF-8-embedded CEMs demonstrated a sieving effect based on differences in ion size and hydration energy, achieving excellent permselectivity for monovalent ions. MCDI tests using the prepared CEMs showed a Na+ ion removal rate exceeding 99% in Na+/Mg2+ and Na+/Ca2+ mixed feed solutions, outperforming a commercial membrane (CSE, Astom Corp., Tokyo, Japan), which achieved a removal rate of 94.1%. These findings are expected to provide valuable insights for advancing not only MCDI but also other electro-membrane processes capable of selectively separating specific ions. Full article
(This article belongs to the Section Membrane Applications for Water Treatment)
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28 pages, 10411 KiB  
Review
Porosity Tunable Metal-Organic Framework (MOF)-Based Composites for Energy Storage Applications: Recent Progress
by Huddad Laeim, Vandana Molahalli, Pongthep Prajongthat, Apichart Pattanaporkratana, Govind Pathak, Busayamas Phettong, Natthawat Hongkarnjanakul and Nattaporn Chattham
Polymers 2025, 17(2), 130; https://doi.org/10.3390/polym17020130 - 8 Jan 2025
Cited by 15 | Viewed by 3689
Abstract
To solve the energy crisis and environmental issues, it is essential to create effective and sustainable energy conversion and storage technologies. Traditional materials for energy conversion and storage however have several drawbacks, such as poor energy density and inadequate efficiency. The advantages of [...] Read more.
To solve the energy crisis and environmental issues, it is essential to create effective and sustainable energy conversion and storage technologies. Traditional materials for energy conversion and storage however have several drawbacks, such as poor energy density and inadequate efficiency. The advantages of MOF-based materials, such as pristine MOFs, also known as porous coordination polymers, MOF composites, and their derivatives, over traditional materials, have been thoroughly investigated. These advantages stem from their high specific surface area, highly adjustable structure, and multifunctional nature. MOFs are promising porous materials for energy storage and conversion technologies, according to research on their many applications. Moreover, MOFs have served as sacrificial materials for the synthesis of different nanostructures for energy applications and as support substrates for metals, metal oxides, semiconductors, and complexes. One of the most intriguing characteristics of MOFs is their porosity, which permits space on the micro- and meso-scales, revealing and limiting their functions. The main goals of MOF research are to create high-porosity MOFs and develop more efficient activation techniques to preserve and access their pore space. This paper examines the porosity tunable mixed and hybrid MOF, pore architecture, physical and chemical properties of tunable MOF, pore conditions, market size of MOF, and the latest development of MOFs as precursors for the synthesis of different nanostructures and their potential uses. Full article
(This article belongs to the Section Polymer Applications)
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10 pages, 2116 KiB  
Article
The Effect of Y Addition on Oxidation Resistance of Bulk W-Cr Alloys
by Anicha Reuban, Jie Chen, Ivan Povstugar, Andrey Litnovsky, Jan Willem Coenen, Christian Linsmeier and Jesus Gonzalez-Julian
Materials 2024, 17(23), 5749; https://doi.org/10.3390/ma17235749 - 24 Nov 2024
Viewed by 816
Abstract
The self-passivating tungsten-based alloy W-11.4Cr-0.6Y (in wt.%) is a potential plasma-facing material for the first wall of future fusion reactors, which has been shown to suppress oxidation of tungsten and withstand temperatures of up to 1000 °C. In this study, the effect of [...] Read more.
The self-passivating tungsten-based alloy W-11.4Cr-0.6Y (in wt.%) is a potential plasma-facing material for the first wall of future fusion reactors, which has been shown to suppress oxidation of tungsten and withstand temperatures of up to 1000 °C. In this study, the effect of Y addition on the microstructure and oxidation behavior of W-11.4Cr alloy at 1000 °C is analyzed by comparing it with W-11.4Cr-0.6Y, both prepared using identical synthesis routes. While the binary W-Cr alloy already exhibits improved oxidation resistance over pure W due to the formation of an outer Cr2WO6 layer, it still shows a tendency for spallation and, hence, is not protective. A continuous passivating chromia layer is only obtained with the addition of Y, and we demonstrate that it results in a 50-fold decrease in the oxide growth rate and eliminates the preferred growth of the oxide at edges seen in the binary alloy. Although a porous, complex oxide scale containing mixed oxide layers and WO3 is formed in both cases, the addition of Y results in lower porosity, which makes the oxide scale more adherent. Full article
(This article belongs to the Section Metals and Alloys)
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20 pages, 5652 KiB  
Article
Synthesis of Plasma-Reduced Graphene Oxide/Lithium Titanate Oxide Composite and Its Application as Lithium-Ion Capacitor Anode Material
by Chan-Gyo Kim, Suk Jekal, Zambaga Otgonbayar, Jiwon Kim, Yoon-Ho Ra, Jungchul Noh, Won-Chun Oh and Chang-Min Yoon
Batteries 2024, 10(9), 311; https://doi.org/10.3390/batteries10090311 - 31 Aug 2024
Cited by 3 | Viewed by 2259
Abstract
A plasma-reduced graphene oxide/lithium titanate oxide (PrGO/LTO) composite is prepared as an anode material to enhance the performance of lithium-ion capacitors (LICs). The PrGO/LTO composite is synthesized by mixing graphene oxide (GO) and LTO, followed by a series of freeze-drying and plasma-treatment processes. [...] Read more.
A plasma-reduced graphene oxide/lithium titanate oxide (PrGO/LTO) composite is prepared as an anode material to enhance the performance of lithium-ion capacitors (LICs). The PrGO/LTO composite is synthesized by mixing graphene oxide (GO) and LTO, followed by a series of freeze-drying and plasma-treatment processes. PrGO forms a porous three-dimensional (3D) structure with a large surface area, effectively preventing the restacking of PrGO while covering LTO. The GO/LTO mixing ratio is controlled to optimize the final structure for LIC applications. In lithium-ion half-cell assembly, the PrGO/LTO-based anode with an 80% mixing ratio exhibits the highest specific capacity of 73.0 mAh g−1 at 20 C. This is attributed to the optimized ratio for achieving high energy density from LTO and high power density from PrGO. In a LIC full-cell comprising PrGO/LTO as the anode and activated carbon as the cathode, the energy and power densities at 1 A g−1 are 40.3 Wh kg−1 and 2000 W kg−1, respectively, with a specific capacitance of 36.3 F g−1 and capacitance retention of 94.1% after 2000 cycles. Its outstanding performance, obtained from incorporating 3D-structured PrGO with LTO at an optimized ratio, lowers the cell resistance and provides efficient lithium-ion diffusion pathways. Full article
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16 pages, 8939 KiB  
Article
CO2 Sorption on Ti-, Zr-, and [Ti,Zr]-Pillared Montmorillonites
by Agnieszka Klimek, Adam Gaweł, Katarzyna Górniak, Anna Tomczyk-Chmiel, Ewa M. Serwicka and Krzysztof Bahranowski
Materials 2024, 17(16), 4036; https://doi.org/10.3390/ma17164036 - 14 Aug 2024
Cited by 4 | Viewed by 973
Abstract
Montmorillonite is a layered clay mineral whose modification by pillaring, i.e., insertion of oxide nanoclusters between the layers, yields porous materials of great potential in sorption and catalysis. In the present study, an unrefined industrial bentonite from Kopernica (Slovakia), containing ca. 70% of [...] Read more.
Montmorillonite is a layered clay mineral whose modification by pillaring, i.e., insertion of oxide nanoclusters between the layers, yields porous materials of great potential in sorption and catalysis. In the present study, an unrefined industrial bentonite from Kopernica (Slovakia), containing ca. 70% of montmorillonite, was used for the preparation of Ti-, Zr-, and mixed [Ti,Zr]-pillared clay sorbents. The pillared samples were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and N2 adsorption at −196 °C and tested for the capacity of CO2 sorption at 0 °C and 1 bar pressure. The experiments revealed that pillared samples sorbed at least four times more CO2 than the parent bentonite. Of the materials tested, the sample pillared with mixed [Ti,Zr] oxide props showed the best performance, which was attributed to its superior microporosity. The results of CO2 adsorption demonstrated that the cost-effective use of crude industrial bentonite as the sorbent precursor is a viable synthesis option. In another experiment, all pillared montmorillonites were subjected to 24 h exposure at room temperature to a flow of dry CO2 and then tested using simultaneous thermal analysis (STA) and the mass spectrometry (MS) analysis of the evolving gases (STA/QMS). It was found that interaction with dry CO2 reduces the amount of bound carbon dioxide and affects the processes of dehydration, dehydroxylation, and the mode of CO2 binding in the pillared structure. Full article
(This article belongs to the Special Issue Advanced Nanoporous and Mesoporous Materials)
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14 pages, 1950 KiB  
Article
One-Pot Phyto-Mediated Synthesis of Fe2O3/Fe3O4 Binary Mixed Nanocomposite Efficiently Applied in Wastewater Remediation by Photo-Fenton Reaction
by Amr A. Essawy, Tamer H. A. Hasanin, Modather. F. Hussein, Emam F. El Agammy and Abd El-Naby I. Essawy
Catalysts 2024, 14(7), 466; https://doi.org/10.3390/catal14070466 - 20 Jul 2024
Cited by 4 | Viewed by 1918
Abstract
A binary Fe2O3/Fe3O4 mixed nanocomposite was prepared by phyto-mediated avenue to be suited in the photo-Fenton photodegradation of methylene blue (MB) in the presence of H2O2. XRD and SEM analyses illustrated that [...] Read more.
A binary Fe2O3/Fe3O4 mixed nanocomposite was prepared by phyto-mediated avenue to be suited in the photo-Fenton photodegradation of methylene blue (MB) in the presence of H2O2. XRD and SEM analyses illustrated that Fe2O3 nanoparticles of average crystallite size 8.43 nm were successfully mixed with plate-like aggregates of Fe3O4 with a 15.1 nm average crystallite size. Moreover, SEM images showed a porous morphology for the binary Fe2O3/Fe3O4 mixed nanocomposite that is favorable for a photocatalyst. EDX and elemental mapping showed intense iron and oxygen peaks, confirming composite purity and symmetrical distribution. FTIR analysis displayed the distinct Fe-O assignments. Moreover, the isotherm of the developed nanocomposite showed slit-shaped pores in loose particulates within plate-like aggregates and a mesoporous pore-size distribution. Thermal gravimetric analysis (TGA) indicated the high thermal stability of the prepared Fe2O3/Fe3O4 binary nanocomposite. The optical properties illustrated a narrowing in the band gab (Eg = 2.92 eV) that enabled considerable absorption in the visible region of solar light. Suiting the developed binary Fe2O3/Fe3O4 nanocomposite in the photo-Fenton reaction along with H2O2 supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. The solar-driven photodegradation reactions were conducted and the estimated rate constants were 0.002, 0.0047, and 0.0143 min−1 when using the Fe2O3/Fe3O4 nanocomposite, pure H2O2, and the Fe2O3/Fe3O4/H2O2 hybrid catalyst, respectively. Therefore, suiting the developed binary Fe2O3/Fe3O4 nanocomposite and H2O2 in photo-Fenton reaction supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. After being subjected to four photo-Fenton degradation cycles, the Fe2O3/Fe3O4 nanocomposite catalyst still functioned admirably. Further evaluation of Fe2O3/Fe3O4 nanocomposite in photocatalytic remediation of contaminated water using a mixture of MB and pyronine Y (PY) dyestuffs revealed substantial dye photodegradation efficiencies. Full article
(This article belongs to the Special Issue Novel Nanocatalysts for Sustainable and Green Chemistry)
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31 pages, 9240 KiB  
Review
State of the Art on Fe Precipitation in Porous Media: Hydrogeochemical Processes and Evolving Parameters
by Wenran Cao, Guanxi Yan, Harald Hofmann and Alexander Scheuermann
J. Mar. Sci. Eng. 2024, 12(4), 690; https://doi.org/10.3390/jmse12040690 - 22 Apr 2024
Cited by 9 | Viewed by 2330
Abstract
The mixing of terrestrial groundwater and seawater creates dynamic reaction zones in intertidal areas, where land-derived Fe(II) is oxidized to Fe(III) and then precipitates as Fe hydroxides at the groundwater–seawater interface. These hydrogeochemical processes contribute to the formation of iron bands at the [...] Read more.
The mixing of terrestrial groundwater and seawater creates dynamic reaction zones in intertidal areas, where land-derived Fe(II) is oxidized to Fe(III) and then precipitates as Fe hydroxides at the groundwater–seawater interface. These hydrogeochemical processes contribute to the formation of iron bands at the saltwater wedge (SW) and beneath the upper saline plume (USP). This study provides a comprehensive review of physical and geochemical processes at field scale in coastal areas, explores the impact of mineral precipitation on pore structure at pore scale, and synthesizes reactive transport modeling (RTM) approaches for illustrating continuum-scale soil physio-chemical parameters during the evolution of porous media. Upon this review, knowledge gaps and research needs are identified. Additionally, challenges and opportunities are presented. Therefore, we reach the conclusion that the incorporation of observational data into a comprehensive physico-mathematical model becomes imperative for capturing the pore-scale processes in porous media and their influence on groundwater flow and solute transport at large scales. Additionally, a synergistic approach, integrating pore-scale modeling and non-invasive imaging, is equally essential for providing detailed insights into intricate fluid–pore–solid interactions for future studies, as well as facilitating the development of regional engineering-scale models and physio-chemical coupled models with diverse applications in marine science and engineering. Full article
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