Artículos (Instituto de Ciencia de Materiales de Sevilla (ICMS) – CIC Cartuja)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10964

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Levofloxacin Degradation, Antimicrobial Activity Decrease, and Potential for Water Disinfection Using Peroxydisulfate Activation by Ag/TiO2 under Sunlight
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Jojoa Sierra, S. D.; Jaramillo Páez, C.; Serna Galvis, E. A.; García Rubio, I.; Hidalgo, M. C.; Navío Santos, José Antonio; Ormad, M. P.; Torres Palma, R. A.; Mosteo, R.; Universidad de Sevilla. Departamento de Química Inorgánica; European Union (UE); Ministerio de Ciencia, Tecnología e Innovación (MINCIENCIAS). Colombia; Ministerio de Ciencia, Tecnología e Innovación (MINCIENCIAS). Colombia
Water quality and usability are global concerns due to microbial and chemical pollution resulting from anthropogenic activities. Therefore, strategies for eliminating contaminants are required. In this context, the removal and decrease in antibiotic activity (AA) associated with levofloxacin (LEV), using TiO2 and Ag/TiO2 catalysts, with and without sunlight and peroxydisulfate, was evaluated. Additionally, the disinfection capacity of catalytic systems was assessed. The catalysts were synthesized and characterized. Moreover, the effect of Ag doping on visible light absorption was determined. Then, the photocatalytic treatment of LEV in water was performed. The materials characterization and EPR analyses revealed that LEV degradation and AA decrease were ascribed to a combined action of solar light, sulfate radical, and photocatalytic activity of the TiO2-based materials. Also, the primary byproducts were elucidated using theoretical analyses (predictions about moieties on LEV more susceptible to being attacked by the degrading species) and experimental techniques (LC-MS), which evidenced transformations on the piperazyl ring, carboxylic acid, and cyclic ether on LEV. Moreover, the AA decrease was linked to the antibiotic transformations. In addition, the combined system (i.e., light/catalyst/peroxydisulfate) was shown to be effective for E. coli inactivation, indicating the versatility of this system for decontamination and disinfection.
Impact of the Biogas Impurities on the Quality of the Precipitated Calcium Carbonate in the Regenaration Stage of a Chemical Absorption Biogas Upgrading Unit
(Elsevier, 2024) Salinero González, Jesús; Gallego Fernández, Luz Marina; Portillo Estévez, Esmeralda; González Arias, Judith; Baena-Moreno, Francisco M.; Navarrete Rubia, Benito; Vilches Arenas, Luis Francisco; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia e Innovación (MICIN). España
Combining Carbon Capture and Storage (CCS) with producing competitive secondary raw materials is key to decarbonizing industry and reducing resource extraction. Biogas upgrading to biomethane stand out as an alternative, but a significant gap remains in integrating this process within a circular economy framework. This issue has been recently addressed by a process that integrates biogas upgrading via caustic absorption with the production of Precipitated Calcium Carbonate (PCC) and the recovery of sodium hydroxide from waste brine solution using membrane technologies. The profitability of this approach depends on the quality of the PCC, a critical factor that this work addresses. By characterizing PCC is determined whether trace compounds in biogas contaminate the PCC and potentially affect its commercial value. It also examines the CO2 absorption process and analyzes the aqueous samples from the filtration phase of the PCC slurry. Results confirm the high purity of PCC obtained from biogas treatment using Raman spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The analyses show that the PCC is pure calcium carbonate, mainly in the stable calcite form, with a typical tetrahedral morphology and no detectable impurities. Characterization of aqueous solutions revealed organic trace compounds from biogas, with TOC concentrations of 9.7 (± 6.4) and 16.0 (± 8) mg C/l. Silicon measurements showed similar concentrations in the absorbent solution and filtrated PCC slurry. Additionally, ammonia escapes as gas, and hydrogen sulfide in the biogas likely contributed to sulfate salt formation. Analysis of the CO₂ absorption shows a first-order reaction with OH-, where the amount of CO₂ absorbed (46.3–50.0 g) closely matches the theoretical value of 48 g. The study reveals that most of the biogas impurities dissolve into the aqueous solution, being crucial for future studies and downstream membrane treatments, and the PCC is unaffected by these impurities with a purity suitable for commercial applications.
Finely Tunable Carbon Nanofiber Catalysts for the Efficient Production of HMF in Biphasic MIBK/H2O Systems
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Bounoukta, Charf Eddine; Megías Sayago, Cristina; Rendón Márquez, Nuria; Ammari, F.; Centeno, M. A.; Ivanova, Svetlana; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España
This work proposes catalytic systems for fructose dehydration to 5-hydroxymethylfurfural using a series of functionalized carbon nanofibers. The catalysts were synthesized via finely selected covalent grafting in order to include a variety of functionalities like pure Bronsted acid, tandem Brønsted/Lewis acid, and tandem Lewis acid/Lewis base catalysts. After the characterization and evaluation of acidity strength and the amount of acid centers, the catalyst series was screened and related to the product distribution. The best-performing catalyst was also used to optimize the reaction parameters in order to achieve 5-hydroxymethylfurfural yields rounding at 60% without significant humin formation.
Effect of Calcination Temperature on the Synthesis of Ni-based Cerium Zirconate for Dry Reforming of Methane
(Elsevier, 2024) Martín Espejo, Juan Luis; Merkouri, Loukia Pantzechroula; Odriozola Gordón, José Antonio; Ramírez Reina, Tomás; Pastor Pérez, Laura; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España
Dry reforming of methane (DRM) represents an alluring approach to the direct conversion of CO2 and CH4, gases with the highest global warming potential, into syngas, a value-added intermediate used in chemical industry. In this study, mixed oxide structures of cerium and zirconium doped with 10 wt% Ni were used due to the high thermal stability. This study showcased the importance of choosing suitable conditions and explored the impact of calcination temperature on Ce–Zr mixed oxides with Ni. XRD analysis confirmed the existence of different crystalline phases according to the calcination temperature. Redox characterisation showed a trade-off among calcination temperature, the dispersion of Ni clusters and its interaction with the support structure. Calcined catalysts at 900 and 1000 °C underwent harsh, long-term DRM conditions. Despite the low surface area of the designed catalysts, the stability experiments proved a relation between dispersion of Ni active phase and catalytic performance, showing an optimum calcination temperature of 1000 °C.
CuOx Supported LaCoO3 Perovskite for the Photoassisted Reverse Water Gas Shift Reaction at Low Temperature
(Elsevier, 2024) Escamilla Rebollo, María; Caballero Martínez, Alfonso; Colón, Gerardo; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España
CuOx/LaCoO3 systems have been studied for the rWGS reaction under thermal assisted photocatalytic conditions within low temperature range of 180–330 ºC. CuOx species deposited from chemical reduction method over LaCoO3 homogeneously covered the perovskite surface. The reduction pretreatment before reaction leads to the partial Co reduction and the complete reduction of Cu. A significant improvement on CO production has been attained upon Cu incorporation. In addition, upon UV–vis irradiation the CO production is also enhanced. Best results have been obtained for 5 wt% Cu. The highest synergistic effect was observed for the lowest temperature, for which catalytic contribution is negligible. Thus, a good compromise is attained at 300 ºC for which a CO production of 5.45 mmol/h·g and 92 % selectivity, showing a good synergistic effect between thermo and thermo-photocatalytic activity.
Influence of the atmosphere on the formation of high-entropy oxides within the Co–Cu–Fe–Mg–Mn–Ni–O system via reactive flash sintering
(Elsevier, 2024-08-05) Manchón Gordon, Alejandro Fernando; Lobo-Llamas, C.; Molina Molina, Sandra; Perejón Pazo, Antonio; Sánchez-Jiménez, P. E.; Pérez-Maqueda, L. A.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Química Inorgánica; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
In this study, the feasibility of preparing quinary equimolar high-entropy oxides within the Co–Cu–Fe–Mg–Mn–Ni–O system was explored using the reactive flash sintering (RFS) technique. Various compositions were tested using this technique under atmosphere pressure, leading to the formation of two primary phases: rock-salt and spinel. Conversely, a new high-entropy oxide was produced as a single-phase material with the composition (Co0.2,Cu0.2,Mg0.2,Mn0.2,Ni0.2)O when RFS experiments were conducted in nitrogen atmosphere. The reducing conditions achieved in nitrogen enabled the incorporation of cations with oxidation states different from +2 into the rock-salt lattice, emphasizing the critical role of the processing atmosphere, whether inert or oxidizing, in the formation of high-entropy oxides. The electrical characterization of this material was obtained via impedance spectroscopy, exhibiting a homogeneous response attributed to electronic conduction with a temperature dependence characteristic of disordered systems.
A zirconia/tantalum biocermet: in vitro and in vivo evaluation for biomedical implant applications
(Royal Society of Chemistry, 2024-08-05) Smirnov, A. I.; Guitián, F; Ramírez Rico, Joaquín; Bartolomé, J. F.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Russian Science Foundation
A biocermet made of zirconia/20 vol% tantalum (3Y-TZP/Ta) is a new composite with exceptional capabilities due to a combination of properties that are rarely achieved in conventional materials (high strength and toughness, cyclic fatigue resistance and flaw tolerance, wear resistance, corrosion resistance, electrical conductivity, etc.). In this study, for the first time, the biomedical performance of a 3Y-TZP/Ta biocermet was evaluated in detail. Its in vitro biocompatibility was assessed using mesenchymal stem cell culture. The effectiveness of in vivo osteointegration of the biocermet was confirmed 6 months after implantation into the proximal tibiae of New Zealand white rabbits. In addition, the possibility of using magnetic resonance imaging (MRI) for medical analysis of the considered biocermet material was studied. The 3Y-TZP/Ta composite showed no injurious effect on cell morphology, extracellular matrix production or cell proliferation. Moreover, the implanted biocermet appeared to be capable of promoting bone growth without adverse reactions. On the other hand, this biocermet demonstrates artefact-free performance in MRI biomedical image analysis studies, making it more suitable for implant applications. These findings open up possibilities for a wide range of applications of these materials in orthopedics, dentistry and other areas such as replacement of hard tissues.
Plasma-flash Sintering: Metastable Phase Stabilization and Evidence of Ionized Species
(John Wiley & Sons, 2025) Gil González, Eva; Taibi, A.; Perejón Pazo, Antonio; Sánchez Jiménez, Pedro Enrique; Pérez Maqueda, L. A.; Universidad de Sevilla. Departamento de Ingeniería Química; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla
The first demonstration of plasma-flash sintering (PFS) is presented in this work. PFS is performed under a low-pressure atmosphere that consecutively generates plasma and flash events. It is shown, by using several combined characterization techniques, that PFS stabilizes metastable phases on the surface of the material, which may be partially, but not solely, attributed to the generation of oxygen vacancies, and induces the absorption of ionized species, if a reactive atmosphere is employed. Even though additional research is required to understand the fundamentals of PFS, it is evidenced its potential to be used as a material surface engineering tool, which may widen the technological capabilities of flash sintering.
Synergistic Effect of He for the Fabrication of Ne and Ar Gas-Charged Silicon Thin Films as Solid Targets for Spectroscopic Studies.
(MDPI, 2024-04-21) Fernández, Asunción; Fortio Godinho, Vanda Cristina; Ávila, José; Jiménez de Haro, María del Carmen; Hufschmidt, Dirk; Lopez-Viejobueno, Jennifer; Ferrer Fernández, Francisco Javier; Asensio, M Carmen; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
Sputtering of silicon in a He magnetron discharge (MS) has been reported as a bottom-up procedure to obtain He-charged silicon films (i.e., He nanobubbles encapsulated in a silicon matrix). The incorporation of heavier noble gases is demonstrated in this work with a synergistic effect, producing increased Ne and Ar incorporations when using He–Ne and He–Ar gas mixtures in the MS process. Microstructural and chemical characterizations are reported using ion beam analysis (IBA) and scanning and transmission electron microscopies (SEM and TEM). In addition to gas incorporation, He promotes the formation of larger nanobubbles. In the case of Ne, high-resolution X-ray photoelectron and absorption spectroscopies (XPS and XAS) are reported, with remarkable dependence of the Ne 1s photoemission and the Ne K-edge absorption on the nanobubble’s size and composition. The gas (He, Ne and Ar)-charged thin films are proposed as “solid” targets for the characterization of spectroscopic properties of noble gases in a confined state without the need for cryogenics or high-pressure anvils devices. Also, their use as targets for nuclear reaction studies is foreseen.
Low CO2 hydrogen streams production from formic acid through control of the reaction pH
(Elsevier, 2023-01-01) Santos, José Luis; Ruiz López, Estela; Ivanova, Svetlana; Monzón, Antonio; Centeno Gallego, Miguel Ángel; Odriozola Gordón, José Antonio; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
There are multiple factors that influence the catalyst performance in the reaction of formic acid dehydrogenation: the nature of catalyst and/or support, the used solvent and reaction variables such as temperature, time, formic acid concentration, presence/absence of formates and pH of the solution. This work evaluates a series of important parameters like the influence of the pH by itself, the influence of the nature of used alkali agents and the effect of direct formate addition as reactive on hydrogen production via formic acid dehydrogenation over a commercially available catalyst. The catalytic performance appears to depend on the ionic radius of the cations of the used base which reflects consequently on the hydrogen selectivity. The best base to be used must have lower hydrated cationic radii and a starting pH around 4 to achieve important hydrogen selectivity for medium term formic acid conversion.
Effect of the sulphonating agent on the catalytic behavior of activated carbons in the dehydration reaction of fructose in DMSO
(Elsevier, 2021-05-05) Bounoukta, Charf Eddine; Megías Sayago, Cristina; Ivanova, Svetlana; Penkova, Anna Dimitrova; Ammari, Fatima; Centeno Gallego, Miguel Ángel; Odriozola Gordón, José Antonio; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España
A series of -SO3R functionalized activated carbons (R=H, O, aryl) were prepared and applied in fructose dehydration reaction to 5-hydroxymethylfurfural. Different sulphonating methods introduce groups on catalyst surface with distinct donor-acceptor and hydrophilic properties. Their nature influences significantly not only activated carbon's textural and chemical properties but also the product yields and selectivity in fructose dehydration reaction. The viability of the solvent free reaction was also investigated and compared to the performance of the catalyst series in presence of DMSO, where the best catalytic results were obtained.
In situ XRD and operando XRD-XANES study of the regeneration of LaCo0.8Cu0.2O3 perovskite for preferential oxidation of CO
(Elsevier, 2024-09) Pereñíguez Rodríguez, Rosa María; Ferri, Davide; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Swiss National Science Foundation (SNFS)
Combinations of perovskite-type oxides with transition and precious metals exhibit remarkable regenerating properties that can be exploited for catalytic applications. The objective of the present work was to study the structural changes experienced by LaCo0.8Cu0.2O3 under reducing/oxidizing atmosphere (redox) and Preferential Oxidation of CO (PrOx, with high H2 concentration) conditions and their reversibility. LaCo0.8Cu0.2O3 was prepared by ultrasonic spray combustion and was characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Structural changes were followed by operando XRD and XAS. Metallic Co and Cu were segregated under both sets of reducing conditions and re-dissolved into the perovskite upon oxidation at 500 °C. Simultaneously, the perovskite-type oxide disappeared under reducing conditions and formed again upon high-temperature oxidation. The effects of this reversible reduction/dissolution of B-site metals on catalyst structure and activity were studied concerning the catalytic process of PrOx. The active phases of cobalt and copper oxides suffer a reduction during the PrOx reaction due to the high H2 concentration; thus, the application of an intermediate oxidation treatment can regenerate the catalytic system and the perovskite can be used for several cycles of reaction and regeneration. In contrast, when this intermediate oxidation treatment is not applied, the catalytic performance decreases in successive activity cycles.
Electrochemical Deposition of Manganese Oxide on Paper-Based Laser-Induced Graphene for the Fabrication of Sustainable High-Energy-Density Supercapacitors
(John Wiley & Sons, 2024-07-24) Klem, Maykel dos Santos; Abreu, Rodrigo; Pinheiro, Tomás; Coelho, João; Alves, Neri; Martins, Rodrigo; Universidad de Sevilla. Departamento de Física de la Materia Condensada; São Paulo Research Foundation (FAPESP); Fundação para a Ciên-cia e a Tecnologia; European Union (UE); Junta de Andalucía
Laser-induced graphene (LIG) is widely used to fabricate microsupercapacitors (MSCs) on various sustainable substrates, such as wood, cork, and lignin. However, the fabrication of MSCs, especially high energy density devices on paper, has rarely been reported. In this work, LIG electrodes are fabricated on wax-coated paper, followed by electrochemical deposition of manganese oxide (MnO2). The obtained LIG/MnO2 supercapacitors exhibit a maximum areal capacitance of 86.9 mF cm−2, while a device with pristine LIG electrodes exhibit a capacitance of 9.1 mF cm−2, both measured at a current density of 0.1 mA cm−2. In addition, the supercapacitor exhibits good cycling stability, retaining 80% of its initial capacitance after 1000 charge/discharge cycles at a current density of 1 mA cm−2. Notably, the LIG/MnO2 supercapacitor exhibits an exceptionally high energy density of 7.3 µWh cm−2 at a power density of 38.8 µW cm−2. In summary, a simple, fast, scalable, reproducible, and energy-efficient fabrication method is represented using electrochemical deposition of manganese oxide on paper-based laser-induced graphene, which are natural, abundant, and sustainable materials, paving the way for large-scale production of environmentally friendly supercapacitors.
Expanding the scope of multiphase-flash sintering: Multi-dogbone configurations and reactive processes
(Elsevier, 2024-07-15) Manchón Gordón, Alejandro F.; Molina Molina, Sandra; Perejón Pazo, Antonio; Alcalde Conejo, A.; Sánchez Jiménez, Pedro Enrique; Pérez Maqueda, Luis Allan; Universidad de Sevilla. Departamento de Química Inorgánica; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España
In this work, we have expanded the possibilities of the multiphase-flash sintering (MPFS) technique by investigating several configurations that involve multiple dogbone specimens (ranging from 1 to 3) and multiple phases (also ranging from 1 to 3). Unlike the traditional MPFS approach using complex 3D or cylindrical samples, this new method allows for a direct comparison with the established conventional flash sintering technique. Our experimental results with dense 8-mol% Yttria-stabilized zirconia demonstrate a significant reduction in the onset temperature as the number of phases and dogbones increases. Building on these findings, we achieved the preparation of pure bulk specimens of SrFe12O19 for the first time through reactive multiphase-flash sintering.
A supervised multiclass framework for mineral classification of Iberian beads
(Public Library of Science, 2024-07-10) Sánchez Gómez, Daniel; Odriozola Lloret, Carlos Patricio; Sousa, Ana Catarina; Garrido Cordero, José Ángel; Romero García, Galo; Martínez Blanes, José María; Edo I. Benaiges, Manel; Villalobos García, Rodrigo; Gonçalves, Victor S.; Universidad de Sevilla. Departamento de Prehistoria y Arqueología; Universidad de Sevilla. Departamento de Química Inorgánica; Fundação para a Ciência e a Tecnologia. Portugal; Ministerio de Ciencia y Tecnología (MCYT). España
Research on personal adornments depends on the reliable characterisation of materials to trace provenance and model complex social networks. However, many analytical techniques require the transfer of materials from the museum to the laboratory, involving high insurance costs and limiting the number of items that can be analysed, making the process of empirical data collection a complicated, expensive and time-consuming routine. In this study, we compiled the largest geochemical dataset of Iberian personal adornments (n = 1243 samples) by coupling X-ray fluorescence compositional data with their respective X-ray diffraction mineral labels. This allowed us to develop a machine learning-based framework for the prediction of bead-forming minerals by training and benchmarking 13 of the most widely used supervised algorithms. As a proof of concept, we developed a multiclass model and evaluated its performance on two assemblages from different Portuguese sites with current mineralogical characterisation: Cova das Lapas (n = 15 samples) and Gruta da Marmota (n = 10 samples). Our results showed that decisión-tres based classifiers outperformed other classification logics given the discriminative importance of some chemical elements in determining the mineral phase, which fits particularly well with the decision-making process of this type of model. The comparison of results between the different validation sets and the proof-of-concept has highlighted the risk of using synthetic data to handle imbalance and the main limitation of the framework: its restrictive class system. We conclude that the presented approach can successfully assist in the mineral classification workflow when specific analyses are not available, saving time and allowing a transparent and straightforward assessment of model predictions. Furthermore, we propose a workflow for the interpretation of predictions using the model outputs as compound responses enabling an uncertainty reduction approach currently used by our team. The Python-based framework is packaged in a public repository and includes all the necessary resources for its reusability without the need for any installation.
Materials for 3D Printed Metal and Metal-Ion Batteries
(John Wiley & Sons, 2024) García Rodríguez, Tomás; Medina Santos, Jesus I.; Coelho, João; Pinilla, Sergio; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Comunidad Autónoma de Madrid; Junta de Andalucía; Science Foundation Ireland
The review provides an overview of the latest innovations, trends, and challenges in the field of 3D-printed metal and metal-ion batteries. It focuses on the materials used in the printing of batteries, including electrodes, electrolytes, and other electroactive components. Compared to other high-quality reviews on the topic, this review provides a broader selection of materials that are expected to gain attention in the next few years, such as redox-active polymers and metal-organic frameworks. This work gives an overview and insight into the latest trends in printing techniques as well as a statistical review of their uses and strengths. We have also gathered the latest works done for each of the material types, and we have taken the opportunity to put them in context and use them to exemplify in which direction is the field going. The review concludes with a critical view of the challenges ahead and a discussion of the direction that the field is taking as well as the external factors that might help to define its future.
Green Fabrication of Stackable Laser-Induced Graphene Micro-Supercapacitors under Ambient Conditions: Toward the Design of Truly Sustainable Technological Platforms
(John Wiley & Sons, 2024) Silvestre, Sara L.; Morais, Maria; Soares, Raquel R. A.; Johnson, Zachary T.; Benson, Eric; Ainsley, Elisabeth; Pham, Veronica; Claussen, Jonathan C.; Gomes, Carmen L.; Martins, Rodrigo; Fortunato, Elvira; Pereira, Luis; Coelho, João; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Fundação para a Ciência e a Tecnologia. Portugal; European Union (UE); Junta de Andalucía; National Science Foundation (NSF)
Extensive research into green technologies is driven by the worldwide push for eco-friendly materials and energy solutions. The focus is on synergies that prioritize sustainability and environmental benefits. This study explores the potential of abundant, non-toxic, and sustainable resources such as paper, lignin-enriched paper, and cork for producing laser-induced graphene (LIG) supercapacitor electrodes with improved capacitance. A single-step methodology using a CO2 laser system is developed for fabricating these electrodes under ambient conditions, providing an environmentally friendly alternative to conventional carbon sources. The resulting green micro-supercapacitors (MSCs) achieve impressive areal capacitance (≈7–10 mF cm−2) and power and energy densities (≈4 μW cm-2 and ≈0.77 µWh cm−2 at 0.01 mA cm−2). Stability tests conducted over 5000 charge–discharge cycles demonstrate a capacitance retention of ≈80–85%, highlighting the device durability. These LIG-based devices offer versatility, allowing voltage output adjustment through stacked and sandwich MSCs configurations (parallel or series), suitable for various large-scale applications. This study demonstrates that it is possible to create high-quality energy storage devices based on biodegradable materials. This development can lead to progress in renewable energy and off-grid technology, as well as a reduction in electronic waste.
Elucidating the Mechanism of Iron-Catalyzed Graphitization: The First Observation of Homogeneous Solid-State Catalysis
(Wiley, 2024) Hunter, Robert D.; Takeguchi, Masaki; Hashimoto, Ayako; Ridings, Kannan M.; Hendy, Shaun C.; Zakharov, Dmitri; Warnken, Nils; Isaacs, Jack; Fernández Muñoz, Sol; Ramírez Rico, Joaquín; Schnepp, Zoe; Universidad de Sevilla. Departamento de Física de la Materia Condensada; University of Birmingham; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; ALBA staff
Carbon is a critical material for existing and emerging energy applications and there is considerable global effort in generating sustainable carbons. A particularly promising area is iron-catalyzed graphitization, which is the conversion of organic matter to graphitic carbon nanostructures by an iron catalyst. In this paper, it is reported that iron-catalyzed graphitization occurs via a new type of mechanism that is called homogeneous solid-state catalysis. Dark field in situ transmission electron microscopy is used to demonstrate that crystalline iron nanoparticles “burrow” through amorphous carbon to generate multiwalled graphitic nanotubes. The process is remarkably fast, particularly given the solid phase of the catalyst, and in situ synchrotron X-ray diffraction is used to demonstrate that graphitization is complete within a few minutes
Al2O3/Y3Al5O12 (YAG)/ZrO2 Composites by Single-step Powder Synthesis and Spark Plasma Sintering
(Elsevier, 2024) Vakhshouri, Maryam; Najafzadehkhoee, Aliasghar; Talimian, Ali; López Pernía, Cristina; Poyato, Rosalía; Gallardo López, Ángela María; Gutiérrez Mora, Felipe; Prnova, Anna; Galusek, Dušan; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Union (UE); JECS Trust
Alumina-yttrium aluminum garnet (YAG)-zirconia composites are often produced by the melt solidification method. In the present study, we investigated the fabrication of α-Al2O3/Y3Al5O12 (YAG)/ZrO2 composite by Spark Plasma Sintering (SPS) of powders synthesized by Pechini's sol-gel method. The ternary composites with homogenous microstructure and high density were produced by SPS at 1300 °C for 15 min. The addition of ZrO2 promoted the sintering of composites, resulting in a higher density and, in turn, higher hardness. A change in the indentation fracture behavior as the result of ZrO2 addition was observed.
Au and Pt Remain Unoxidized on a CeO2-Based Catalyst during the Water-Gas Shift Reaction
(American Chemical Society, 2022-01-12) Ramírez Reina, Tomás; González Castaño, Míriam; López Flores, Víctor; Martínez Tejada, Leidy Marcela; Zitolo, Andrea; Ivanova, Svetlana; Xu, Wenquian; Centeno Gallego, Miguel Ángel; Rodriguez, Jose A.; Odriozola Gordón, José Antonio; Universidad de Sevilla. Departamento de Química Inorgánica; Department of Energy. United States; Ministerio de Ciencia e Innovación (MICIN). España
The active forms of Au and Pt in CeO2-based catalysts for the water-gas shift (WGS) reaction are an issue that remains unclear, although it has been widely studied. On one hand, ionic species might be responsible for weakening the Ce-O bonds, thus increasing the oxygen mobility and WGS activity. On the other hand, the close contact of Au or Pt atoms with CeO2 oxygen vacancies at the metal-CeO2 interface might provide the active sites for an efficient reaction. In this work, using in situ X-ray absorption spectroscopy, we demonstrate that both Au and Pt remain unoxidized during the reaction. Remarkable differences involving the dynamics established by both species under WGS atmospheres were recognized. For the prereduced Pt catalyst, the increase of the conversion coincided with a restructuration of the Pt atoms into cuboctahedrical metallic particles without significant variations on the overall particle size. Contrary to the relatively static behavior of Pt0, Au0 nanoparticles exhibited a sequence of particle splitting and agglomeration while maintaining a zero oxidation state despite not being located in a metallic environment during the process. High WGS activity was obtained when Au atoms were surrounded by oxygen. The fact that Au preserves its unoxidized state indicates that the chemical interaction between Au and oxygen must be necessarily electrostatic and that such an electrostatic interaction is fundamental for a top performance in the WGS process

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