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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Ion Mobility and Segregation in Seed Surfaces Subjected to Cold Plasma Treatments
(American Chemical Society, 2025-02-24) Perea Brenes, Álvaro; Ruiz Pino, Natalia; Yubero, Francisco; Garcia, José Luis; Rodríguez González-Elipe, Agustín; Gómez Ramírez, Ana María; Prados Montaño, Antonio; López Santos, Carmen; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Union (UE); Universidad de Sevilla; Junta de Andalucía
Plasma treatment of seeds is an efficient procedure to accelerate germination, to improve initial stages of plant growth, and for protection against pathogen infection. Most studies relate these beneficial effects with biochemical modifications affecting the metabolism and genetic growth factors of seeds and young plants. Using barley seeds, in this work, we investigate the redistribution of ions in the seed surface upon their treatment with cold air plasmas. In addition, we investigate the effect of plasma in the lixiviation of ions through the seeds’ hull when they are immersed in water. Ion redistribution in the outer layers of air plasmatreated seeds has been experimentally determined through X-ray photoelectron spectroscopy analysis in combination with in-depth chemical profiling with gas cluster ion beams. The results show that in the shallowest layers of the seed hull (at least up to a depth of ∼100 nm) there is an enrichment of K+ and Ca2+ ions, in addition to changes in the O/C and N/C atomic ratios. These data have been confirmed by the electron microscopy/fluorescence analysis of seed cuts. Observations have been accounted for by a Monte Carlo model, simulating the electrostatic interactions that develop between the negative charge accumulated at the seed surface due to the interaction with the plasma sheath and the positive ions existing in the interior. Furthermore, it is shown that upon water immersion of plasma-treated seeds mobilized ions tend to lixiviate more efficiently than in pristine seeds. The detection of a significant concentration of NO3− anions in the water has been attributed to a secondary reaction of nitrogen species incorporated into the seeds during plasma exposure with reactive oxygen species formed on their surface during this treatment. The implications of these findings for the improvement of the germination capacity of seeds are discussed.
Comparing 3He content in magnetron sputtered and implanted targets for nuclear studies
(Springer, 2025-05-25) Pilotto, E,; Ferrer Fernández, Francisco Javier; Akhmadaliev, S.; Fernández, A.; Gadea, A.; Camacho, J.; Valiente Dobón, J. J.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Agencia Estatal de Investigación. España; Generalitat Valenciana
3He targets are a valuable tool in nuclear physics, particularly for studying nuclear structure and dynamics via direct reactions in inverse kinematics. However, they are often prone to degradation under intense beam irradiation and have insufficient 3He content for use with lowintensity exotic beams. In a recent AGATA experiment at LNL, designed to study the astrophysically relevant lifetime of a 15O excited state, two types of 3He targets were tested. One was produced using ion implantation and the other with a novel magnetron sputtering technique, in both cases on Au substrates. Following irradiation with a stable 16O beam, they were characterized using Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA). Results demonstrated that, under the here used fabrication conditions, sputtered targets present a higher 3He content, while implanted ones exhibit thinner profiles. This highlights the possibilities and complementarity of these targets, suggesting their tailored use for future experimental campaigns.
A hypervalent metal MOF catalyst as an avenue to go beyond heterogeneous Fenton-like processes for organic contaminant removal in water
(Royal Society of Chemistry, 2025-05-01) Santos Juanes, Lucas; Rodríguez Sánchez, Noelia; Rodríguez Gómez, Salvador; Núñez, Nuria O.; Arqués, Antonio; Ruiz-Salvador, A. Rabdel; Ballesteros, Menta; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España
Metal–organic frameworks (MOFs) have recently been proposed as a plausible solution to the pressing issue of water scarcity and as a means of remediating contaminated water bodies. In light-assisted water treatment, they have so far only been exploited via the hydroxyl radical route, through Fenton-like processes. A new avenue is introduced here by the biomimetic conceptual design of MOF bearing hypervalent metal atoms for photocatalytic water treatment. We report a zeolitic imidazole framework (ZIF) material doped with iron (Fe-ZIF-7-III; UPO-4) synthesized via a novel mild treatment to stabilize photoactive hypervalent ferryl ions for the first time in a MOF for water treatment. The successful synthesis of the 2D material and the adequate incorporation of iron into the structure were demonstrated using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). A simulation study analyzed the structure and stability of the Fe-ZIF-7-III material as well as the involvement of ferryl ions in the photo-Fenton-type process. Furthermore, the calculated band gap of this material shows its viability for use in photocatalysis using sunlight. This was confirmed by evaluating the photodegradation of caffeine, a model pollutant in water, without the assistance of hydroxyl radicals as indicated by a scavenger test. The recyclability test revealed that Fe-ZIF-7-III could be used continuously with effective catalytic activity, thus opening the door to the field of studying hypervalent metal MOFs not yet explored in water treatment.
Gas temperature equation in a high-frequency argon plasma column at low pressures
(American Institute of Physics, 2002-01) Palmero Acebedo, Alberto; Cotrino Bautista, José; Barranco Quero, Ángel; Rodríguez González-Elipe, Agustín; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Comisión Interministerial de Ciencia y Tecnología (CICYT). España; European Union (UE)
Using a collisional-radiative model and taking into account an energy balance equation in a surface-wave-produced and -sustained argon plasma, it is possible to obtain the dependence of the gas temperature on the plasma parameters. If only heat conduction and radiative losses are considered for the neutral system, as well as the interaction with the electrons, the plasma parameters that determine the gas temperature will be the elastic absorbed power per electron and the electron number density. In a first approximation the axial dependence of the neutral gas temperature can be considered lineal with the product of these two parameters.
Collisional radiative model of an argon atmospheric capillary surface-wave discharge
(American Institute of Physics, 2004-11-03) Yanguas Gil, A.; Cotrino Bautista, José; Rodríguez González-Elipe, Agustín; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Dirección General de Investigación Científica y Técnica (DGICYT). España
The characteristics of a microwave surface-wave sustained plasma operated at atmospheric pressure in an open-ended dielectric tube are investigated theoretically as a first step in the development of a self-consistent model for these discharges. The plasma column is sustained in flowing argon. A surface-wave discharge that fills the whole radial cross section of the discharge tube is considered. With experimental electron temperature profiles [García et al., Spectrochim. Acta, Part B 55, 1733 (2000)] the numerical model is used to test the validity of the different approximations and to study the influence of the different kinetic processes and power loss mechanisms on the discharge.
Catalytic performance of NiCo-CePr oxide on FeCrAlloy micromonoliths in hydrogen production by oxidative steam reforming of ethanol
(Elsevier, 2025-10-01) Rodríguez, César; Martínez Tejada, Leidy Marcela; Centeno Gallego, Miguel Ángel; Moreno, Sonia; Molina, Rafael; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad Nacional de Colombia
The conformation of a NiCo catalyst promoted by CePr on FeCrAlloy thermally pretreated micromonoliths was investigated via washcoating using a colloidal suspension of the catalytic precursor (hydrotalcite, HT) without the use of additives. A high affinity was established between the nature of the reconstructed HT and the layer of the formed alumina microstructures obtained after thermal treatment, which exhibited high material adhesion. The effect of the amount of catalyst incorporated into the sinusoidal microchannels of monoliths was also investigated. The catalytic performance was evaluated for the production of H2 from oxidative steam reforming of ethanol (OSRE) and compared with that of a powder catalyst (slurry) and an uncoated micromonolith. The results indicated notable benefits from the micromonoliths, especially when incorporating low amounts of catalyst with low layer thicknesses-LT (8 g·L-1, layer thickness ∼ 0.3 µm), achieved a hydrogen yield of 2.86 molH2·molEtOH-1, comparable to that of the powder catalyst benchmark (2.91 molH2·molEtOH-1), but with enhanced stability at 65 h and improved heat and mass transport characteristics. Overall, this study opens the way for the promising feasibility of scaling up the OSRE reaction to produce H2.
Impact of Tb4+ and morphology on the Thermal Evolution of Tb-doped TiO2 Nanostructured Hollow Spheres and Nanoparticles
(Elsevier, 2021-02-05) Colomer, M. T.; Rodríguez, E.; Morán Pedroso, María; Vattier Lagarrigue, María Florencia; Andrés, A. de; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Union (UE)
Tb-doped TiO2 hollow spheres (HSs) in the range 0.0-2.0 at.% have been,synthesized by the first time to the best of our knowledge. The HSs are compared with,nanoparticles (NPs) to evaluate the impact of morphology on their physicochemical and,photoluminescence (PL) behavior upon increasing calcination temperature. After,calcination at 550ºC, the particles are anatase with a primary average size of 10.0 ± 0.2,nm for the NPs and 12.0 ± 0.2 nm for those that form the micron sized hollow spheres of,1.8 µm diameter and ca. 64 nm shell thickness. The temperature of the anatase–rutile,transition is found to be strongly dependent on the presence of Tb as well as on,morphology. Contrarily to the usual stabilization of anatase when doping with trivalent,rare-earth ions, the transition temperature is reduced when doping with Tb. The rutile,phase is further favored for the HSs compared to the NPs probably related to the low,density of the HSs and/or a more efficient packing of the nanoparticles that form those,spheres with respect to the packing of the NPs. A slight unit-cell volume decrease for the,anatase structure is observed upon Tb doping, in both the NPs and in the HSs, contrary to,the expected increment due to the larger ionic radius of Tb3+ compared to Ti4+,. In addition,,2,the intensity of the characteristic f-f Tb3+ emission bands is extremely weak both in the,anatase and rutile phases. The transition is accompanied with the emergence of an infrared,emission band centered at 810 nm related to the formation of defects during the structural,transformation providing deep levels in the gap that partly quench the f-f emissions in the,rutile phase. The results are consistent with the presence of Tb in both +3 and +4 valence,states. XPS measurements confirmed the presence of Tb3+ as well as of Tb4+ in both HSs,and NPs with a Tb4+ fraction that increases with increasing Tb doping. The large fraction,of Tb4+ present in the samples originates the weak f-f emission intensity, the slight,decrease of the cell parameters and the destabilization of the anatase phase
Selective H/D Exchange in E–H (E = Si, Ge, Sn) Bonds Catalyzed by 1,2,3-Triazolylidene-Stabilized Nickel Nanoparticles
(American Chemical Society, 2025) Molinillo, Pablo; Gálvez Del Postigo, Ana; Puyo, Maxime; Vattier Lagarrigue, María Florencia; Beltrán, Ana M.; Rendón Márquez, Nuria; Lara Muñoz, Patricia; Suárez, Andrés; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
Nickel nanoparticles (Ni·MIC) stabilized with mesoionic 1,2,3-triazolylidene (MIC) ligands were prepared via decomposition of the [Ni(COD)2] (COD = 1,5-cyclooctadiene) complex with H2 (3 bar) in the presence of 0.2 or 0.5 equiv of ligand. The obtained monodisperse and small-sized (3.2–3.8 nm) nanoparticles were characterized by high-resolution transmission electron microscopy (TEM, HRTEM) and inductively coupled plasma (ICP) analysis. Further analysis of the nickel nanoparticles by X-ray photoelectron spectroscopy (XPS) demonstrated the coordination of the MIC ligands to the metal surface. Finally, the Ni·MIC nanoparticles were applied in the isotopic H/D exchange in hydrides of group 14 elements (Si, Ge, Sn) using D2 gas under relatively mild conditions (1.0–1.8 mol % Ni, 1 bar D2, 55 °C). High and chemoselective deuterium incorporation at the E–H (E = Si, Ge, Sn) bond in these derivatives was observed.
Quantification of the H Content in Diamondlike Carbon and Polymeric Thin Films by Reflection Electron Energy Loss Spectroscopy
(American Institute of Physics, 2005) Yubero, Francisco; Rico, Víctor; Espinós Manzano, Juan Pedro; Cotrino Bautista, José; Rodríguez González-Elipe, Agustín; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Educación y Ciencia (MEC). España
A nondestructive method to determine the hydrogen content at the surface of diamondlike carbon and polymeric thin films is proposed. The method relies on the analysis of the elastic peak produced by backscattering of electrons from the hydrogen atoms present at the sample surface. Quantitative analysis of the H content at the surface is achieved through use of a phenomenological sensitivity factor for elastic electron backscattering by H atoms with respect to other atoms present at the surface of reference polymeric samples. The validity of the method is checked with elastic recoil detection measurements and infrared spectroscopy analysis of the same samples. The accuracy of the method in the determination of H content at the sample surface is estimated to be ±10%.
Pyroelectric Potassium Hydrogen Malate with Polarized Hydrogen Bond Chains and Aligned Dipole Moments
(American Institute of Physics, 2008) de Matos Gomes, E.; Belsley, M. S.; Criado Vega, Alberto; Rodrigues, V. H.; Costa, M. M.R.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Fundação para a Ciência e a Tecnologia. Portugal
A spontaneous polarization of 16 μC/ cm2 at room temperature has been found in the semiorganic crystal potassium hydrogen malate (KHC 4H4O5 · H2O). This high polarization results from a structural arrangement of oriented dipoles formed by the potassium cations and the COO- group from the malate anion, and long hydrogen bonded polarized chains created by the hydrogen L-malate anion via O-H⋯O interactions, directed along the polar sixfold axis. The material shows a second harmonic generation with a rotationally averaged effective second order susceptibility equal to 0.70 of potassium dihydrogen phosphate at an incident wavelength of 1064 nm.
Formation of the complete range of Ti5Si3-xGe x solid solutions via mechanically induced self-sustained reactions
(Elsevier, 2011-11) Córdoba Gallego, José Manuel; Chicardi Augusto, Ernesto; Avilés Escaño, Miguel Ángel; Gotor Martínez, Francisco José; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Agencia Estatal de Investigación. España
The complete range of Ti5Si3-Ti5Ge 3 solid solutions was synthesised from elemental mixtures of Ti, Si, and Ge under an inert atmosphere via mechanically induced self-sustaining reactions (MSR). The stoichiometry of Ti5Si3-xGe x solid solutions was controlled by adjusting the Si/Ge ratio of the initial mixture. The chemical composition and lattice parameters of the materials confirmed that Ti5Si3-Ti5Ge 3 solid solutions with good chemical homogeneity could be produced via MSR.
V2O5/TiO2 Catalyst for Catalytic Glucose Oxidation to Formic Acid in Batch Reactor: Vanadium Species Nature and Reaction Conditions Optimization
(Springer, 2024-07-04) Álvarez Hernández, Débora; Ivanova, Svetlana; Domínguez Leal, María Isabel; Martínez Blanes, José María; Centeno Gallego, Miguel Ángel; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Union (UE)
This study focused on the development of vanadium-based catalysts for formic acid production from glucose. The influence of different vanadium precursors on the catalytic activity of titania supported catalysts was contemplated and compared to the performance of commercial and synthesized unsupported V2O5. The obtained results reveal a successful deposition of multiple vanadium species on TiO2 as confirmed by XRD, Raman, and UV-Vis measurements. Catalyst screening identifies V5+ species as main player indicating its important oxidizing potential. Afterwards, the key reaction conditions, as temperature, time, pressure and catalyst loading, were optimized as well as the state of the catalyst after the reaction characterized.
Fabrication of Al2O3-Y3Al5O12-ZrO2 composites by single-step spark plasma sintering
(Elsevier, 2025-03-12) Vakhshouri, Maryam; Talimian, Ali; Najafzadehkhoee, Aliasghar; Gallardo López, Ángela María; Poyato, Rosalía; Gutiérrez Mora, Felipe; Galusek, Dušan; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Union (UE)
Fabricating Al2O3-Y3Al5O12-ZrO2 ceramic composites with a eutectic microstructure is challenging and costly, as it requires high-temperature melting of precursor materials. Here, we report on the successful production of Al2O3-Y3Al5O12- 5 mol% ZrO2 composites with lamellar eutectic microstructure through single-step spark plasma sintering (SPS) of sol-gel synthesized powder. The release of volatile species from partially calcined powders, due to limited calcination at 1000°C for 2 h, as well as their fine particle size, were used to create the conditions for local electric discharge and plasma formation during SPS; this resulted in the local formation of eutectic liquids, enabling the formation of lamellar microstructures. The microstructural features can be tailored by modifying the calcination process.
Solid-state spectroscopic, thermokinetics and thermal analysis of aceclofenac coordination complexes with lanthanum and gadolinium
(Soc Brasileira Quimica, 2024-05-24) Melo, Laís D. S. M. K; Carvalho, Cláudio T.; Sánchez Jiménez, Pedro Enrique ; Sequinel, Thiago; Perejón Pazo, Antonio; Pérez Maqueda, Luis Allan ; Colman, Tiago A. D.; Universidad de Sevilla. Departamento de Química Inorgánica; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Brasil; Finaciadora de Estudos e Projetos (FINEP). Brasil
In recent years, the field of coordination chemistry has experienced a surge in interest regarding the synthesis and characterization of coordination complexes for diverse applications. This study is dedicated to investigating coordination compounds resulting from the interaction of nonsteroidal anti-inflammatory drugs (NSAIDs) with metal ions. The study research places significant emphasis on understanding the stability and thermal behavior of these coordination compounds. The utilization of thermoanalytical techniques is crucial in achieving this goal. Thermal analysis and thermokinetics provide valuable insights into the underlying mechanisms, kinetics, and energetics of these reactions, thereby facilitating the optimization of synthesis procedures. The research employs concurrent techniques, namely thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), to explore the thermal stability and decomposition pathways of these coordination compounds. Thermokinetic models and optimization methodologies are subsequently applied to identify key reaction parameters. The primary aim of this research is to unveil the thermal behavior, stability, and reaction kinetics of aceclofenac coordination compounds, thus contributing significantly to the understanding of thermokinetics and thermal analysis in the domain of coordination chemistry. Specifically, this study is focused on aceclofenac coordination complexes involving lanthanum and gadolinium, with the ultimate goal of advancing the field of coordination chemistry
Integrated CO2 capture and dynamic catalysis for CO2 recycling in a microbrewery
(Elsevier, 2025-02) Merkouri, Loukia Pantzechroula; Bobadilla Baladrón, Luis Francisco; Martín Espejo, Juan Luis; Odriozola Gordón, José Antonio; Penkova, Anna Dimitrova; Torres Sempere, Guillermo; Ramírez Reina, Tomás; Short, Michael; Duyar, Melis S.; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Union (UE)
In this study, we used fermentation off-gases from a brewery for integrated CO2 capture and utilisation in order to produce CH4 with a dual-function material (DFM) containing NiRu as catalyst and dispersed CaO as adsorbent. CH4 was produced from captured CO2 via 2 pathways (fast and slow), proceeding through formyl intermediates according to the operando DRIFTS-MS results. The NiRuCa DFM showed a stable CH4 capacity over 8 cycles (105 μmol/gDFM) with fermentation off-gases being used as a CO2 capture feed. H2O and O2, which were present in small amounts in the emissions feed, resulted in the passivation of Ni in the form of a NiO layer and hence, the DFM did not undergo excessive oxidation and deactivation. This work constitutes a first in terms of validating the use of DFMs with real industrial emissions, and it directly correlates the DFM activity performance with its reaction mechanism and intermediate species.
Improving the photocatalytic degradation of EDTMP: Effect of doped NPs (Na, Y, and K) into the lattice of modified Au/TiO2 nano-catalysts
(Elsevier, 2025-01) Riedel, Ramona; Schowarte, Julia; Semisch, Laura; González Castaño, Míriam; Ivanova, Svetlana; Arellano-García, Harvey; Martienssen, Marion; Universidad de Sevilla. Departamento de Química Inorgánica
This study presents the photocatalytic degradation of the aminophosphonate ethylenediaminetetra(methylenephosphonic acid) (EDTMP) with a range of different doped nanoparticles (NP). The photocatalysts were based on TiO2 benchmark P25 and gold (Au) doped either with sodium (Na), potassium (K) or yttrium (Y). The synthesized photocatalysts were characterized via TEM, XRF, XRD, UV-DRS (band gap estimation) and N2-physisorption. Photocatalytic pre-screening at pH values of 3, 7 and 10 indicated highest o-PO4 release of EDTMP at pH 7 and 10 for NP either doped with K or Y. The results of LC/MS analysis showed that the NPs doped with 5 % Y (Au2/Y5/P25) resulted in the fastest degradation of EDTMP. The target compound was completely degraded within 60 min, 4 times faster than photochemical treatment of unadulterated EDTMP. Importantly, also the transformation products were accelerated by the photocatalytic treatment with Au2/P25 either doped with 5 % Y or 10 % K. The results of scavenger experiments indicated that the enhanced photocatalytic degradation of EDTMP is primarily attributable to the presence of hydroxyl radicals in the bulk and to a lesser extent to •O2 − and electron-holes (h+) at the surface of the catalysts. The study demonstrates that the catalytic efficiency of TiO2 nanocomposites is significantly influenced by the choice of dopants, which affect particle size, band gap, and photocatalytic activity. Yttrium at low concentrations (i.e., 5 wt% Y) doping emerged as particularly effective, enhancing both the visible light absorption and h+ separation, leading to superior photocatalytic performance in the degradation of EDTMP. The Au content also plays a crucial role in enhancing the photocatalytic efficiency. However, the combination of Au and Na doping was found to be less effective for this photocatalysis in aqueous media, potentially due to larger particle sizes and insufficient dopant contents. In conclusion, the findings emphasise the necessity of optimising both the selection of dopants and the design of catalysts in order to enhance photocatalytic applications.
Improved CO selectivity during CO2 hydrogenation by bimetallic copper-cobalt supported SBA-15
(Elsevier, 2025-02) Escamilla, María; Caballero Martínez, Alfonso; Colón, Gerardo; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Union (UE)
Co-Cu/SBA-15 systems have been studied for the reverse water gas shift (rWGS) reaction within mild temperature range of 250–650 ºC. CuOx and CoOx species at different weight ratios were deposited from wet impregnation method over SBA-15 support. We have stated that pre-reduction treatment before reaction leads to the complete Co and Cu reduction for Co-Cu/SBA systems. A low copper content on Co/SBA system leads to similar CO2 conversion than monometallic Co-catalyst. However, competitive Sabatier side reaction appears almost suppressed. So, upon Cu incorporation a significant improvement on CO yield has been attained with respect to Co/SBA catalyst. Thus, a good compromise is attained at 450 ºC using Co5Cu5/SBA catalyst for which a stable CO2 conversion of 22 % and 97 % CO selectivity has been obtained under lowest H2:CO2 ratio.
Direct biogas methanation at moderate pressure: Mechanism investigation over Ni-based catalysts
(Elsevier, 2025-03) Giarnieri, Ilenia; Chen, Sining; Ballesteros Plata, Daniel; Holgado, Juan P.; Maluta, Francesco; Caballero Martínez, Alfonso; Mata Benito, Patricia; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Union (UE); Junta de Andalucía
Direct upgrading of biogas by CO2 methanation aims to produce a gas to be injected into the grid. Operating at moderate pressures favors thermodynamics, but catalyst surface and reaction mechanism under realistic conditions are not well investigated. We study the role of basic and metallic sites on performance and mechanism of clean biogas methanation (CO2/CH4=1/1 v/v) at 1, 5 and 7 bar. Ni/Mg/La/Al hydrotalcite-derived catalysts, with different Ni and La contents, are investigated combining tests and physico-chemical characterization, including quasi-in situ XPS at 7 bar, with CO2-adsorption and methanation DRIFTS at 1 and 7 bar, respectively. An optimized catalyst (6.5 wt% La, 35 wt% Ni) with 3–4 nm Ni0 and balanced basicity, achieves 96 LCH4*gcat− 1 * h− 1 (300◦C, 7 bar). DRIFTS confirm catalysts activity experimental trend. Optimizing Ni and La results in higher consumption rates of formate intermediate and sufficient Ni0 sites for CO formation. Increasing pressure to 7 bar promotes CO and m-HCOO reactivity.
Effect of Temperature Variations on Equilibrium Distances in Levitating Parallel Dielectric Plates Interacting through Casimir Forces
(American Institute of Physics (AIP), 2016) Esteso Carrizo, Victoria; Carretero Palacios, Sol; Míguez, Hernán; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Union (UE); Ministerio de Economía y Competitividad (MINECO). España
We study at thermal equilibrium the effect of temperature deviations around room temperature on the equilibrium distance (deq) at which thin films made of Teflon, silica, or polystyrene immersed in glycerol levitate over a silicon substrate due to the balance of Casimir, gravity, and buoyancy forces. We find that the equilibrium nature (stable or unstable) of deq is preserved under temperature changes, and provide simple rules to predict whether the new equilibrium position will occur closer to or further from the substrate at the new temperature. These rules depend on the static permittivities of all materials comprised in the system (ϵ0(m)) and the equilibrium nature of deq. Our designed dielectric configuration is excellent for experimental observation of thermal effects on the Casimir force indirectly detected through the tunable equilibrium distances (with slab thickness and material properties) in levitation mode.
Textile microfibers valorization by catalytic hydrothermal carbonization toward high-tech carbonaceous materials
(American Association for the Advancement of Science, 2024-11-18) Parrilla Lahoz, Silvia; Zambrano, Marielis C.; Pawlak, Joel J.; Venditti, Richard A.; Ramírez Reina, Tomás; Odriozola Gordón, José Antonio; Duyar, Melis S.; Universidad de Sevilla. Departamento de Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Next Generation Europe
Microplastics fibers shed from washing synthetic textiles are released directly into the waters and make up 35% of primary microplastics discharged to the aquatic environment. While filtration devices and regulations are in development, safe disposal methods remain absent. Herein, we investigate catalytic hydrothermal carbonization (HTC) as a means of integrating this waste (0.28 million tons of microfibers per year) into the circular economy by catalytic upcycling to carbon nanomaterials. Herein, we show that cotton and polyester can be converted to filamentous solid carbon nanostructures using a Fe-Ni catalyst during HTC. Results revealed the conversion of microfibers into amorphous and graphitic carbon structures, including carbon nanotubes from a cotton/polyethylene terephthalate (PET) mixture. HTC at 200°C and 22 bar pressure produced graphitic carbon in all samples, demonstrating that mixed microfiber wastes can be valorized to provide potentially valuable carbon structures by modifying reaction parameters and catalyst formulation.

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