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

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

Examinar

Mostrando 1 - 20 de 665

Boosting water activation determining-step in WGS reaction on structured catalyst by Mo-doping
(Elsevier, 2022-01-01) García Moncada, Nuria; García Moncada, Nuria; Martínez Tejada, Leidy Marcela; Romero Sarria, Francisca; Odriozola Gordón, José Antonio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España
Proton conductors Mo-Eu-Zr mixed oxide systems were synthesized and further mixed with a conventional Pt/CeO2/Al2O3 catalyst to develop a highly efficient water-gas-shift (WGS) catalyst. The designed catalyst, once structured, allows reach the equilibrium conversion at medium temperatures (∼350 °C) at 80 L·g−1 h−1 space velocity. The ability of the proton conductor to maintain an elevated water concentration at the metal-support interface by Grotthuss’ mechanism boosts the catalytic activity in WGS reaction. The Mo-containing proton conductor is extensively characterized allowing to establish the formation of molybdenum oxide phases nucleating on top of the Eu sites in Eu-Zr oxide solid solution. [MoO4]2− to [Mo7O24]6− clusters nucleates at low Mo contents resulting in a α-MoO3 layer on increasing its content. In presence of H2, Mo-bronzes are formed from ∼200 °C enhancing water concentration at the surfaces and boosting the catalytic activity in the WGS reaction. These results pave the way for developing lower volume WGS reactors.
The effect of support surface hydroxyls on selective CO methanation with Ru based catalysts
(Elsevier, 2022-07-05) Martínez Tejada, Leidy Marcela; Muñoz Bernabé, Antonio; Pérez Flores, Alejandro; Laguna Espitia, Óscar Hernando; Bobadilla Baladrón, Luis Francisco; Centeno, Miguel Ángel; Odriozola Gordón, José Antonio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España
The aim of this work was to clarify the effect of the support on CO selective methanation with Ru/TiO2 catalysts. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity should be ascribed to anatase:rutile ratio, RuO2 +TiO2 solid solution formation, as well as the metal content and the thermal treatment used. All these characteristics result in active and selective catalysts in which the suppression of the reverse water gas shift reaction was observed. The catalytic performance must be explained by both the formation of more active Ru species as a result of support influence and the higher Ru dispersion. The study allows to conclude that for CO activation the role of support surface hydroxyls seems to be determinant for both the activity and selectivity of Ru/TiO2 catalysts.
Metal micromonoliths for the cleaning of H2 by means of methanation reactions
(ELsevier, 2022-01-01) Laguna Espitia, Óscar Hernando; Muñoz Murillo, Ara; Bobadilla Baladrón, Luis Francisco; Martínez Tejada, Leidy Marcela; Montes, M.; Centeno, M. A.; Odriozola Gordón, José Antonio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España
The present manuscript presents for the first time the structuring of a Ru/TiO2 catalyst that was achieved by means of the washcoating procedure using homemade metal micromonoliths (Fecralloy®) of 1330 cpsi. For this, an optimized formulation of the slurried catalyst as well as a reproducible protocol for the coating of the micromonoliths were successfully achieved. The obtained structured systems were tested in the selective CO methanation reaction and the effect of different variables over the catalytic performance were analyzed such as the amount of loaded catalyst in the micromonoliths, the temperature of reaction, the space velocity, and the amount of CO and H2 within the feed-stream. The study of all of these parameters allowed to establish optimal conditions to maximize the performance of the structured Ru/TiO2 catalyst and subsequently, this was tested under those cited conditions in long-term tests (∼375 h), including shut-down/start-up cycles, aiming to evaluate its catalytic stability. The system presented a considerable stability along the different test without loss of catalytic activity, being specially remarkable its resistance to the inclusion of shut-down/start-up cycles. Therefore, this study lays the foundations for future development of more sophisticated structured systems for the selective CO methanation based on the structuring strategy proposed.
Electrochemical tailoring of graphite properties for tunable catalytic selectivity of glucose conversion to 5-hydroxymethylfurfural
(Elsevier, 2024-10-30) Delgado Martín, Gabriel; Bounoukta, Charf Eddine; Ivanova, Svetlana; Centeno Gallego, Miguel Ángel; Villar-Rodil, Silvia; Paredes, Juan Ignacio; García-Dalí, Sergio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia e Innovación (MICIN). España
This study presents a novel approach for boosting the selectivity of 5-hydroxymethylfurfural (HMF) production from glucose through electrochemical modification of graphite materials. Three distinct graphitic substrates were subjected to controlled electrochemical treatments utilizing sodium sulfate or phosphoric acid as electrolytes. The process expanded the graphite particles/pieces and introduced oxygenated functional groups to the exposed surfaces while preserving the structural integrity of the bulk material. The resulting modifications influenced the type and quantity of Lewis and Brønsted acidic sites, providing exhaustive control over reaction pathways leading to HMF. This electrochemically modified graphite demonstrated superior tunability compared to traditional metal-based catalysts, enabling dynamic optimization of reaction conditions for enhanced HMF yield. The controlled introduction of functional groups facilitated the tailoring of active sites, significantly impacting the kinetics of glucose conversion and achieving HMF selectivity up to 95%. This level of precision in controlling catalytic properties is essential for maximizing HMF yield while minimizing undesired by-product formation, addressing a critical challenge in HMF production.
Highly effective non-noble MnO2 catalysts for 5- hydroxymethylfurfural oxidation to 2,5- furandicarboxylic acid
(Wiley, 2024-03-05) Álvarez Hernández, Débora; Megías Sayago, Cristina; Penkova, Anna Dimitrova; Centeno Gallego, Miguel Ángel; Ivanova, Svetlana; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España
Noble metal-free catalyst or catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid are proposed in this study as a proposal to solve one of the great disadvantages of this reaction of using preferably noble metal-based catalysts. The catalytic activity of six MnO2 crystal structures is studied as alternative. The obtained results showed a strong connection between catalytic activity the type of MnO2 structure organization and redox behavior. Among all tested catalysts, ϵ-MnO2 showed the best performance with an excellent yield of 74 % of 2,5-furandicarboxylic acid at full -hydroxymethylfurfural conversion.
Multifunctional sustainable carbon catalyst for glucose to fructose isomerization reaction
(Wiley, 2025-04-23) Bounoukta, Charf Eddine; Lara, Beatriz; Delgado Martín, Gabriel; Domínguez Leal, María Isabel; Penkova, Anna Dimitrova; Centeno Gallego, Miguel Ángel; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía
Two series of functionalized activated carbons have been prepared and used for the glucose to fructose isomerization reaction. Alkali earth chlorides and alkali halides have been chosen for the functionalization with the final goal to study the effect of cation and anion variation on isomerization activity. A part of the samples has been subjected to an activation procedure giving rise to the formation of new active sites of a distinct type and composition. The active site nature and density greatly influenced the reaction mechanism, giving rise to combined pathways catalyst with increased activity and fructose selectivity. The functionalization with MgCl2 resulted in a very stable and performant catalyst with an optimal fructose yield of 33% at 140 °C in only 20 min reaction time and during four cycles of reutilization.
Mechanistic Insights into the Conversion of Glucose to Formic Acid over Vanadium-based Catalyst
(Elsevier, 2025-06-01) Álvarez-Hernández, Débora; Ivanova, Svetlana; Centeno Gallego, Miguel Ángel; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España
The catalytic oxidation of biomass-derived compounds represents a promising and sustainable pathway for the production of valuable chemicals, such as formic acid, which is a key candidate for hydrogen storage and CO₂-neutral energy applications. This study investigates the selective oxidation of glucose to formic acid using vanadium oxide supported on titania (VOx/TiO₂) as the catalytic system. This paper elucidates the reaction mechanism and analyzes the product distribution over time under controlled experimental conditions. The system exhibited selective glucose conversion, with formic acid emerging as the primary product, followed by intermediates such as arabinose, glyceraldehyde, acetic acid, and formaldehyde. Mechanistic studies suggested that the selective formation of formic acid proceeds via successive C1–C2 bond cleavage assisted by the peroxo species of vanadium. These findings highlight the key role of molecular and activated oxygen in the reaction pathway, while excluding the direct decomposition pathways for formic acid. This mechanistic insight and the role of vanadium-based peroxo species formed on the catalyst surface provide a critical foundation for optimizing catalyst design for biomass conversion processes.
Pursuing efficient systems for glucose transformation to levulinic acid: Homogeneous vs. heterogeneous catalysts and the effect of their co-action
(Elsevier, 2022-06-15) Bounoukta, Charf Eddine; Megías Sayago, Cristina; Ivanova, Svetlana; Ammari, Fatima; Centeno Gallego, Miguel Angel; Odriozola Gordón, José Antonio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia e Innovación (MICIN). España
Exploring available catalytic systems to understand their behavior is a must to properly design efficient catalysts aiming to definitively drive biomass from laboratory to industrial scale. Glucose transformation to levulinic acid involves cascade reactions with specific requirements, different active sites in each case and secondary reactions hard to avoid which are intrinsically linked to the catalyst’s nature and reaction conditions. In the present work, homogeneous, heterogeneous and heterogeneous/homogeneous catalysts are considered with the unique goal of improving levulinic acid yield while understanding the catalytic behaviour of cost-effective catalysts. The choice of the catalytic systems and the effect of the main reaction parameters on activity and selectivity is studied and discussed.
Interfacial Chemistry Limits the Stability of Deep Blue Perovskite LEDs Revealed by Operando Characterization
(American Chemical Society, 2025) Mirabelli, A. J.; Kammlander, B.; Lu, Y.; Varma, R. M.; Gu, Q. C.; Radetzky, K.; Selby, T. A.; Liu, T. J.; Riva, S.; Wei, Z. M.; Anaya Martín, Miguel; Stranks, S. D.; Física de la Materia Condensada; Swedish Research Council; Swedish Energy Agency; European Research Council (ERC); European Union (UE). H2020; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Engineering and Physical Sciences Research Council (UK); Royal Society (UK); Tata Group; Diamond Light Source. UK
To commercialize lead halide perovskites as light-emitting diodes (LEDs), the operational device lifetime needs to be drastically improved. For this to be achieved, an understanding of degradation behavior under bias is crucial. Herein, we perform operando measurements of the structural, chemical, and electronic changes using synchrotron-based grazing-incidence wide-angle X-ray scattering and hard X-ray photoelectron spectroscopy on full-stack deep blue mixed bromide/chloride lead halide perovskite LEDs. While a clear drop in optoelectronic performance is recorded under electrical bias, the accompanying X-ray scattering data reveals only minor changes in structural properties. However, photoelectron spectroscopy reveals substantial chemical changes at the electron-injecting interface after bias is applied, including the formation of unwanted metallic lead and a new chlorine species that is not in the perovskite structure. These operando approaches give important structural and interfacial perspectives to reveal the degradation mechanisms in these LEDs and highlight the need to address the top electron-injecting interface to realize step-changes in operational stability.
Hard X‑ray Photoelectron Spectroscopy Probing Fe Segregation during the Oxygen Evolution Reaction
(ACS Publications, 2024-10) Longo, Filippo; Lloreda Jurado, Pedro Javier; Gil-Rostra, Jorge; Gonzalez-Elipe, Agustín R.; Yubero, Francisco; Thomä, Sabrina L J
NiFe electrocatalysts are among the most active phases for water splitting with regard to the alkaline oxygen evolution reaction (OER). The interplay between Ni and Fe, both at the surface and in the subsurface of the catalyst, is crucial to understanding such outstanding properties and remains a subject of debate. Various phenomena, ranging from the formation of oxides/(oxy)hydroxides to the associated segregation of certain species, occur during the electrochemical reactions and add another dimension of complexity that hinders the rational design of electrodes for water splitting. In this work, we have developed the procedure for the quantification of chemical depth profiling by XPS/HAXPES measurements and applied it to two NiFe electrodes with different porosities. The main outcome of this study is related to the surface reconstruction of the electrodes during the OER, followed at two different depths by means of X-ray photoelectron spectroscopy. We find that Fe initially segregates at the surface when exposed to ambient conditions, resulting in the formation of an inactive FeOx phase. In addition, the porosity of the catalyst plays a significant role in the segregation process and thus in the performance of the electrode. In particular, the higher porosity of the nanostructured sample is responsible for a more pronounced diffusion of Fe from the subsurface to the surface with a more effective suppression of the activity of the Ni1–xFexOOH phase. These results highlight the importance of the fact that the chemical state of the surface of a multielement system is a snapshot in time, dependent on both external parameters, such as the applied potential and the adjacent electrolyte, and the underlying bulk properties accessible with HAXPES.
Microstructural control by freeze-casting of CaO architectures for improved and stable thermochemical energy storage performance
(Elsevier, 2025-07-30) Amghar, Nabil; Ivorra-Martinez, Juan; Perejón Pazo, Antonio; Hanaor, Dorian; Gurlo, Aleksander; Ramírez Rico, Joaquín; Pérez Maqueda, Luis Allan; Sánchez Jiménez, Pedro Enrique; Química Inorgánica; Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España
This study investigates the development of porous calcium-based monoliths via freeze-casting (FC) as a novel approach for thermochemical energy storage, particularly within the Calcium Looping (CaL) process. The freeze-casting technique enabled the fabrication of scaffolds with controlled porosity using polyvinyl alcohol (PVA) as a binder. Experimental results demonstrated that freeze-cast monoliths exhibited superior multicycle performance under various carbonation and calcination conditions. The FC-CaCO3 monolith achieved the highest residual conversion of 68.1 % under mild vacuum calcination conditions (780 °C, 0.1 bar CO2), significantly surpassing other configurations. Tests conducted in an inert atmosphere also yielded favorable results, with a conversion of 56.1 %, outperforming equivalent raw powder samples. The enhanced performance is attributed to improved CO2 interaction with the porous structure, mitigating sintering effects and preserving active surface area. Morphological observations by X-ray tomography and SEM confirmed limited particle sintering after multiple cycles, maintaining a reactive surface that supported consistent conversion rates. The pore size distribution of the material evolves upon cycling resulting in an increased microporosity, while the pore network maintains a low tortuosity (τ ~ 1.5–2.0). The addition of dopants such as ZrO2 and SiO2 did not enhance performance, as the monoliths' inherent structure provided sufficient stability. These findings highlight freeze-casting as a promising method for creating advanced porous materials suitable for energy storage applications.
Graphene exfoliation in cyrene for the sustainable production of microsupercapacitors
(Institute of Physics Publishing Ltd., 2025-04-22) Moreira, Pedro; Carvalho, Davide; Abreu, Rodrigo; Alba Carranza, María Dolores; Ramírez Rico, Joaquín; Fortunato, Elvira; Martins, Raúl A.; Pinto, Joana V.; Carlos, Emanuel; Coelho, João; Física de la Materia Condensada; Fundaçao para a Ciencia e a Tecnologia (FCT); Junta de Andalucía; European Union
Graphene and its composites have attracted much attention for applications in energy storage systems. However, the toxic solvents required for the exfoliation process have hampered the exploitation of its properties. In this work, graphene dispersions are obtained via liquid phase exfoliation (LPE) of graphite in cyrene, an environmentally friendly solvent with solubility parameters like those of N-methyl-2-pirrolidone. The obtained dispersions with a concentration of 0.2 mg ml−1 comprised multilayered graphene sheets with lateral sizes in the hundreds of nanometers, as confirmed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Mixing the obtained dispersions with ethanol made it possible to collect the graphene, which was redispersed in 2-Propanol. This active material was used to fabricate supercapacitor electrodes using a scalable spray deposition method on carbon nanotube (CNT) current collectors with the aid of vinyl masks. The device, tested with a PVA/LiCl gel electrolyte, achieved a specific capacitance of 3.4 mF cm−2 (0.015 mA cm−2). In addition, the devices show excellent cycling stability (>10 000 cycles at 0.5 mA cm−2) and good mechanical properties, losing less than 10% of initial capacitance after 1000 bending cycles. This work demonstrates the adaptability of liquid-phase exfoliation to produce graphene sustainably, providing the proof-of-concept for further 2D materials processing and green microsupercapacitor (MSC) fabrication.
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; Física Atómica, Molecular y Nuclear; 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.; 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; 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; 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; 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; 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; Física de la Materia Condensada; 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; Química Inorgánica; 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.

Examinar

Envíos recientes