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2021


New Trends in Nanoclay-Modified Sensors


Pavon, E; Martin-Rodriguez, R; Perdigon, AC; Alba, MD
Inorganics, 9 (2021) 43
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT ▼

Nanoclays are widespread materials characterized by a layered structure in the nano-scale range. They have multiple applications in diverse scientific and industrial areas, mainly due to their swelling capacity, cation exchange capacity, and plasticity. Due to the cation exchange capacity, nanoclays can serve as host matrices for the stabilization of several molecules and, thus, they can be used as sensors by incorporating electroactive ions, biomolecules as enzymes, or fluorescence probes. In this review, the most recent applications as bioanalyte sensors are addressed, focusing on two main detection systems: electrochemical and optical methods. Particularly, the application of electrochemical sensors with clay-modified electrodes (CLME) for pesticide detection is described. Moreover, recent advances of both electrochemical and optical sensors based on nanoclays for diverse bioanalytes' detection such as glucose, H2O2, organic acids, proteins, or bacteria are also discussed. As it can be seen from this review, nanoclays can become a key factor in sensors' development, creating an emerging technology for the detection of bioanalytes, with application in both environmental and biomedical fields.


Junio, 2021 | DOI: 10.3390/inorganics9060043

Unveiling mechanochemistry: Kinematic-kinetic approach for the prediction of mechanically induced reactions


Gil-González, E.; Rodríguez-Laguna, M.d.R.; Sánchez-Jiménez, P.E.; Perejón, A.; Pérez-Maqueda, L.A.
Journal of Alloys and Compounds, 866 (2021) 158925
Reactividad de Sólidos

ABSTRACT ▼

Mechanochemistry has attracted a lot of attention over the last few decades with a rapid growth in the number of publications due to its unique features. However, very little is known about how mechanical energy is converted into chemical energy. Most of the published works using mechanochemistry neglect the required attention to the experimental parameters and their effect over the resulting products, what makes extremely difficult to reproduce the results from lab to lab. Moreover, if it is taken into consideration the broad range of experimental conditions used in different studies, it is quite difficult to compare results and set optimum conditions. As a result, mechanochemistry is generally viewed as a "black box". The aim of this work is to provide some insight into mechanochemistry. Thus, a simple kinematic-kinetic approach that allows the full parametrization of mechanically induced reactions is proposed. In an analogous way to thermally activated process, it is shown that kinetic modeling can serve to parametrize and model mechanically induced reactions as a function of the milling parameters with great reliability, thereby gaining prediction capability. As a way of example, this methodology has been applied for the first time to the mechanochemical reaction of Co and Sb to form CoSb3, a skutterudite-type thermoelectric material. Moreover, the universality of this methodology has also been validated with data from the literature. A key feature of the proposed kinematic-kinetic approach is that it can be extrapolated to other mechanically induced reactions, either inorganic or organic. 


Junio, 2021 | DOI: 10.1016/j.jallcom.2021.158925

Thermal behaviour of the different parts of almond shells as waste biomass


Garzon, E; Arce, C; Callejon-Ferre, AJ; Perez-Falcon, JM; Sanchez-Soto, PJ
Journal of Thermal Analysis and Calorimetry, (2021)
Materiales Avanzados

ABSTRACT ▼

The main aim of this study is to investigate the thermal behaviour of the different parts of almond shells produced in an almond industry as a waste biomass. For this purpose, several experiments have been conducted under laboratory conditions. After removing the mature almonds, the waste raw materials subject of this study were treated with distilled water (10 min) and separated in several parts. Taking into account their physical characteristics, they were: (a) complete shells: exocarp, mesocarp and endocarp without grinding (Sample C); (b) ground samples of complete shells, sieved under 0.2 mm (Sample M); (c) hard layers of the endocarp (Sample E); (d) internal layers of the endocarp (Sample I); and (e) mature drupes (Sample P) or skin, being constituted by the flexible part of green colour (fresh form) or yellow (after drying). The thermal behaviour of all these sample materials has been investigated using a laboratory furnace, with determination of ash contents and mass loss by progressive heating (120 min of holding time). Elemental and DTA-TG/DTG analyses of selected sample materials have been carried out. Although a complete study can be very complex, a first approach has been performed in this investigation. Results on thermal decomposition of this biomass waste have been presented to emphasize the main differences between sample materials of almond shells. These results have demonstrated the influence of several parameters, such as the particle size, and previous treatments in the thermal behaviour of the different parts of the almond shells, as showed in this investigation. Structural analysis of almond shells allowed to determine lignin, cellulose and hemicellulose. From the lignin content, it has been predicted the higher heating value (18.24 MJkg(-1)) of this waste as by-product of industrial interest. Other linear correlations to calculate this parameter have been applied with similar results in all these samples.


Junio, 2021 | DOI: 10.1007/s10973-021-10940-x

Features of coupled AgBr/WO3 materials as potential photocatalysts


Puga, F.; Navío, J.A.; Hidalgo, M.C.
Journal of Alloys and Compounds, 867 (2021) 159191
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT ▼

AgBr/WO3 composite photocatalysts with different selected molar AgBr/WO3 ratios were prepared and widely characterized by XRD, N2-adsorption, SEM, TEM, UV–visible/DRS and XPS techniques. The samples were tested using rhodamine B (RhB) or caffeine, under two illumination conditions (UV and visible light). Although AgBr and WO3 pristine materials have relatively low band gap values (2.6 eV and 2.8 eV, respectively), they exhibit low or no photocatalytic activity under visible light, at least for caffeine degradation. This fact may be mainly related to a high recombination rate of photogenerated charge carriers in these samples. However, the coupling of both leads to a substantial improvement in the degradation of caffeine and RhB under both UV and visible lighting conditions. The increased photocatalytic activity found in the coupled systems with respect to the pristine materials can be attributed to the formation of a type II heterostructure in the coupled AgBr/WO3 samples. Our results show that for AgBr/WO3 coupled systems, kinetic degradation profiles have clear dependence on the molar percentages of the coupled pristine materials, as well as on the nature (sensitizing or not sensitizing effect) of the substrate. For caffeine photodegradation, the best performance was obtained when AgBr/WO3(10–15%) catalysts were used. The AgBr/WO3(20%) sample showed the best photocatalytic activity for rhodamine B degradation, exhibiting also excellent dark adsorption capacity (40–45%). Additionally, studies of activity in five consecutive tests showed a good RhB degradation during the successive reuses being involving a N-de-ethylation mechanism with the main O2•− radicals participation; relatively low mineralization percentages were observed, both under UV and visible light conditions. In these successive runs, no silver leaching to the medium was observed but a change from AgBr towards Ag2CO3 and/or AgxO was produced at the catalyst surface. These features should be known in the use of these systems as potential photocatalysts for practical applications.


Junio, 2021 | DOI: 10.1016/j.jallcom.2021.159191

Swelling layered minerals applications: A solid state NMR overview


Pavon, E; Alba, MD
Progress in Nuclear Magnetic Resonance Spectroscopy, 124 (2021) 99-128
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

ABSTRACT ▼

Swelling layered clay minerals form an important sub-group of the phyllosilicate family. They are characterized by their ability to expand or contract in the presence or absence of water. This property makes them useful for a variety of applications, ranging from environmental technologies to heteroge-neous catalysis, and including pharmaceutical and industrial applications. Solid State Nuclear Magnetic Resonance (SS-NMR) has been extensively applied in the characterization of these materials, providing useful information on their dynamics and structure that is inaccessible using other characterization methods such as X-ray diffraction. In this review, we present the key contributions of SS-NMR to the understanding of the mechanisms that govern some of the main applications associated to swelling clay minerals. The article is divided in two parts. The first part presents SS-NMR conventional applications to layered clay minerals, while the second part comprises an in-depth review of the information that SS-NMR can provide about the different properties of swelling layered clay minerals.


Junio, 2021 | DOI: 10.1016/j.pnmrs.2021.04.001

High-temperature solar-selective coatings based on Cr(Al)N. Part 1: Microstructure and optical properties of CrNy and Cr1-xAlxNy films prepared by DC/HiPIMS


Rojas, TC; Caro, A; Lozano, G.; Sanchez-Lopez, JC
Solar Energy Materials and Solar Cells, 223 (2021) 110951
Tribología y Protección de Superficies - Materiales Ópticos Multifuncionales

ABSTRACT ▼

In order to explore the potentialities of Cr1-x(Al)xNy materials in multilayer-based solar selective coatings (SSC) for high temperature applications (T > 500 °C), the optical behavior of Cr1-x(Al)xNy films is studied in this work. Two sets of layers (CrNy and Cr1-xAlxNy) were prepared by direct current (DC) and high-power impulse magnetron sputtering (HiPIMS) technology. The deposition parameters: N2 flux, HiPIMS frequency and aluminum sputtering power, were modified to get a wide variety of stoichiometries. The composition, morphology, phases and electronic structure of the films were characterized in depth. The optical behavior was determined by UV–Vis–NIR and FTIR spectroscopies, and the optical constants were obtained from the measured transmittance and reflectance spectra based on appropriate dielectric function models. Our results indicate that small changes in the layer composition influence the optical constants. In particular, a metallic-like behavior was obtained for CrNy layers with N vacancies (CrN0.95 and CrN0.67 films) while a semiconductor-like behavior was observed for CrN1.08. Thus, the CrNy films can be used as effective absorber layer in multilayer-based SSC, and namely, the CrN0.67 film as an IR reflector/absorber layer too. Likewise, the optical properties of Cr1-xAlxNy layers can also be tuned from metallic to semiconductor-like behavior depending on the chemical composition. Indeed, the absorption coefficients of Cr1-xAlxNy films with optimized Al content and N-vacancies are comparable to those reported for state-of-the-art materials such as TiAlN or TiAlCrN. In addition, a Cr0.96Al0.04N0.89 film was found to be a suitable IR reflector/absorber layer.


Mayo, 2021 | DOI: 10.1016/j.solmat.2020.110951

Mössbauer study of iron gall inks on historical documents


Lerf, A; Wagner, FE; Dreher, M; Espejo, T; Perez-Rodriguez, JL
Heritage Science, 9 (2021) 49

ABSTRACT ▼

Iron gall ink was used in the Western world as a permanent writing material already in late Roman times and throughout the Middle Ages, until it became obsolete in the twentieth century. There is much interest in experimental methods to determine the state of the ink and its degradation products on historical documents. Mossbauer spectroscopy with Fe-57 is such a method, and it has the particular advantage to be sensitive to the chemical bonding of iron, but this method has only rarely been applied to historical documents. In this paper we present Mossbauer data for two damaged documents from a Library in Granada and a handwritten German book from the eighteenth century. In addition to the inked parts of the manuscripts, ink-free parts were studied to determine the amount and chemical state of the iron in the papers. These new results are discussed in the context of previously published Mossbauer data. In one of the investigated documents Fe(II)-oxalate, FeC2O4 center dot 2H(2)O, was observed. The assignment of the various Fe3+ sites in the different documents is rather difficult and often there is a superposition of various species. Known forms of iron gallate are definitely not present on the inked papers. The observed ferric species can be remains of Fe3+ polyphenol complexes of the ink, complexes of Fe3+ with degradation products of the cellulose of the paper or gum arabic, or very small iron oxide or hydroxide nanoparticles.


Mayo, 2021 | DOI: 10.1186/s40494-021-00522-3

Synthesis and Characterization of a Nearly Single Bulk Ti2AlN MAX Phase Obtained from Ti/AlN Powder Mixture through Spark Plasma Sintering


Salvo, C; Chicardi, E; Poyato, R; Garcia-Garrido, C; Jimenez, JA; Lopez-Pernia, C; Tobosque, P; Mangalaraja, RV
Materials, 14 (2021) 2217
Reactividad de Sólidos

ABSTRACT ▼

MAX phases are an advanced class of ceramics based on ternary carbides or nitrides that combine some of the ceramic and metallic properties, which make them potential candidate materials for many engineering applications under severe conditions. The present work reports the successful synthesis of nearly single bulk Ti2AlN MAX phase (>98% purity) through solid-state reaction and from a Ti and AlN powder mixture in a molar ratio of 2:1 as starting materials. The mixture of Ti and AlN powders was subjected to reactive spark plasma sintering (SPS) under 30 MPa at 1200 degrees C and 1300 degrees C for 10 min in a vacuum atmosphere. It was found that the massive formation of Al2O3 particles at the grain boundaries during sintering inhibits the development of the Ti2AlN MAX phase in the outer zone of the samples. The effect of sintering temperature on the microstructure and mechanical properties of the Ti2AlN MAX phase was investigated and discussed.


Mayo, 2021 | DOI: 10.3390/ma14092217

Effect of the sulphonating agent on the catalytic behavior of activated carbons in the dehydration reaction of fructose in DMSO


Bounoukta, CE; Megias-Sayago, C; Ivanova, S; Penkova, A; Ammari, F; Centeno, MA; Odriozola, JA
Applied Catalysis A-General, 617 (2021) 118108
Química de Superficies y Catálisis

ABSTRACT ▼

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.


Mayo, 2021 | DOI: 10.1016/j.apcata.2021.118108

Effects of an Illite Clay Substitution on Geopolymer Synthesis as an Alternative to Metakaolin


Eliche-Quesada, D; Bonet-Martinez, E; Perez-Villarejo, L; Castro, E; Sanchez-Soto, PJ
Journal of Materials in Civil Engineering, 33 (2021) 04021072
Materiales Avanzados

ABSTRACT ▼

In this study, a calcined illite clay from Bailen, Jaen, Spain, was valorized as a substitute of metakaolin in the synthesis of new geopolymeric materials. The raw materials, raw clay and commercial kaolin, were pretreated at 750 degrees C (4 h). Several samples (0%-100% by weight of clay) were activated by mixing NaOH solution and sodium silicate solution. The specimens were cured (60 degrees C and 99% relative humidity) for 24 h, then demolded and kept at ambient conditions for 7, 28, and 90 days. The prepared geopolymers were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Physical, mechanical, and thermal properties were determined. The results indicated that the specimens based on the illite raw clay and metakaolin present an amorphous consolidated appearance, characteristic of the polycondensation reactions. The incorporation of up to 50% by weight of raw clay provided geopolymers with higher mechanical strength (39.6 MPa) and bulk density (1,455 kg/m(3)), lower apparent porosity (19.6%), and similar although slightly higher thermal conductivity (0.25 W/mK) than control geopolymers containing only metakaolin as a precursor after 28 days of curing. Control geopolymers presented compressive strength, bulk density, apparent porosity, and thermal conductivity of 23 MPa, 1,251 kg/m(3), 41.03% and 0.224 W/mk, respectively, at the same age of cured geopolymers. The mechanical properties increased with curing time due to a greater advance of the geopolymerization reaction. Therefore, this illite clay can be thermally activated together with metakaolin to obtain geopolymers with suitable technological properties. The results demonstrate that the finished materials can be used for construction applications.


Mayo, 2021 | DOI: 10.1061/(ASCE)MT.1943-5533.0003690

IR spectroscopic insights into the coking-resistance effect of potassium on nickel-based catalyst during dry reforming of methane


Azancot, L; Bobadilla, LF; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 285 (2021) 119822
Química de Superficies y Catálisis

ABSTRACT ▼

Dry reforming of methane (DRM) is an effective catalytic route for transforming CO2 and CH4 into valuable syngas and thus potentially attractive for mitigating the emission of environmental harmful gases. Therefore, it is crucial to develop rationally Ni-based catalysts highly resistant to coking and sintering. In this scenario, the addition of small amounts of potassium to nickel catalyst increases their resistance to coking during dry reforming of methane. Nonetheless, the specific role of potassium in these catalysts not have been fully understood and there are still important discrepancies between the different reported studies. This work provides a new approach on the anticoking nature of a K-promoted Ni catalyst by means of a combined IR spectroscopic study of in situ characterization by CO adsorption under static conditions and operando DRIFTS measurements under dynamic conditions of DRM reaction. The involved surface species formed during the reaction were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that the existence of Ni-K interfacial sites favours the gasification of carbonaceous deposits towards reverse Boudouard reaction and reduces the sticking probability of CO2 dissociative adsorption. Moreover, the presence of strongly Mg-O-K basic sites leads to the formation of carbonate intermediates that are subsequently reduced into CO gaseous towards the associative mechanism by RWGS reaction. These results provide a fundamental understanding of the relevant anticoking effect of potassium on Ni-based catalysts.


Mayo, 2021 | DOI: 10.1016/j.apcatb.2020.119822

Mechanochemically synthesized ternary chalcogenide Cu3SbS4 powders in a laboratory and an industrial mill


Dutkova, E; Sayagues, MJ; Fabian, M; Balaz, M; Achimovicova, M
Materials Letters, 291 (2021) 129566
Reactividad de Sólidos

ABSTRACT ▼

In this work, we demonstrate the use of elemental precursors (Cu, Sb, S) to synthesize famatinite Cu3SbS4 using a laboratory planetary ball milling and an industrial eccentric vibratory milling. Cu3SbS4 was prepared for 120 min and 180 min in laboratory and industrial mill, respectively, with the utilization of protective atmosphere. The Cu3SbS4 prepared in the laboratory and industrial mill with crystallite size 14 nm and 10 nm, respectively, was confirmed by both LeBail refinement of the X-ray powder diffraction data and transmission electron microscopy. The determined band gap energy 1.31 eV and 1.24 eV is blue-shifted relative to the bulk Cu3SbS4. The synthesis of Cu3SbS4 by a scalable milling process represents a prospective route for mass production of material with potential photovoltaic properties. In this work, we demonstrate the use of elemental precursors (Cu, Sb, S) to synthesize famatinite Cu3SbS4 using a laboratory planetary ball milling and an industrial eccentric vibratory milling. Cu3SbS4 was prepared for 120 min and 180 min in laboratory and industrial mill, respectively, with the utilization of protective atmosphere. The Cu3SbS4 prepared in the laboratory and industrial mill with crystallite size 14 nm and 10 nm, respectively, was confirmed by both LeBail refinement of the X-ray powder diffraction data and transmission electron microscopy. The determined band gap energy 1.31 eV and 1.24 eV is blue-shifted relative to the bulk Cu3SbS4. The synthesis of Cu3SbS4 by a scalable milling process represents a prospective route for mass production of material with potential photovoltaic properties. 


Mayo, 2021 | DOI: 10.1016/j.matlet.2021.129566

Toward Commercialization of Stable Devices: An Overview on Encapsulation of Hybrid Organic-Inorganic Perovskite Solar Cells


Aranda, Clara A.; Calio, Laura; Salado, Manuel
Crystals, 11 (2021) 519
Materiales Ópticos Multifuncionales

ABSTRACT ▼

Perovskite solar cells (PSCs) represent a promising technology for energy harvesting due to high power conversion efficiencies up to 26%, easy manufacturing, and convenient deposition techniques, leading to added advantages over other contemporary competitors. In order to promote this technology toward commercialization though, stability issues need to be addressed. Lately, many researchers have explored several techniques to improve the stability of the environmentally-sensitive perovskite solar devices. Challenges posed by environmental factors like moisture, oxygen, temperature, and UV-light exposure, could be overcome by device encapsulation. This review focuses the attention on the different materials, methods, and requirements for suitable encapsulated perovskite solar cells. A depth analysis on the current stability tests is also included, since accurate and reliable testing conditions are needed in order to reduce mismatching involved in reporting the efficiencies of PSC.


Mayo, 2021 | DOI: 10.3390/cryst11050519

Understanding the opportunities of metal-organic frameworks (MOFs) for CO2 capture and gas-phase CO2 conversion processes: a comprehensive overview


Gandara-Loe, J; Pastor-Perez, L; Bobadilla, LF; Odriozola, JA; Reina, TR
Reaction Chemistry & Engineering, 6 (2021) 787-814
Química de Superficies y Catálisis

ABSTRACT ▼

The rapid increase in the concentration of atmospheric carbon dioxide is one of the most pressing problems facing our planet. This challenge has motivated the development of different strategies not only in the reduction of CO2 concentrations via green energy alternatives but also in the capture and conversion of CO2 into value-added products. Metal-organic frameworks (MOFs) are a relatively new class of porous materials with unique structural characteristics such as high surface areas, chemical tunability and stability, and have been extensively studied as promising materials to address this challenge. This comprehensive review identifies the specific structural and chemical properties of MOFs that result in advanced CO2 capture capacities and fairly encouraging catalytic CO2 conversion behaviour. More importantly, we describe an interconnection among the unique properties of MOFs and the engineering aspects of these intriguing materials towards CO2 capture and conversion processes.


Mayo, 2021 | DOI: 10.1039/d1re00034a

Structural Evolution in Iron-Catalyzed Graphitization of Hard Carbons


Gomez-Martin, A; Schnepp, Z; Ramirez-Rico, J
Chemistry of Materials, 33 (2021) 3087-3097
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT ▼

Despite the recent interest in catalytic graphitization to obtain graphite-like materials from hard-carbon sources, many aspects of its mechanism are still poorly unknown. We performed a series of in situ experiments to study phase transformations during graphitization of a hard-carbon precursor using an iron catalyst at temperatures up to 1100 degrees C and ex situ total scattering experiments up to 2000 degrees C to study the structural evolution of the resulting graphitized carbon. Our results show that upon heating and cooling, iron undergoes a series of reductions to form hematite, magnetite, and wustite before forming a carbide that later decomposes into metallic iron and additional graphite and that the graphitization fraction increases with increasing peak temperature. Structural development with temperature results in decreasing sheet curvature and increased stacking, along with a decrease in turbostratic disorder up to 1600 degrees C. Higher graphitization temperatures result in larger graphitic domains without further ordering of the graphene sheets. Our results have implications for the synthesis of novel biomass-derived carbon materials with enhanced crystallinity.


Mayo, 2021 | DOI: 10.1021/acs.chemmater.0c04385

Synthesis of clay geopolymers using olive pomace fly ash as an alternative activator. Influence of the additional commercial alkaline activator used


Gomez-Casero, MA; Moral-Moral, FJ; Perez-Villarejo, L; Sanchez-Soto, PJ; Eliche-Quesada, D
Journal of Materials Research and Technology-JMR&T 12 (2021) 1762-1776
Materiales Avanzados

ABSTRACT ▼

In this research, the use of olive pomace fly ash (OPFA) as an alkaline source for the activation of calcined clays (CC) from Bailen (Jaen, Spain) was studied. The optimal composition was obtained for 70 wt % CC and 30 wt % OPFA. The physical, mechanical and thermal properties of control geopolymers that use water as a liquid medium have been studied and compared with geopolymers that use additional activating solutions as sodium or potassium hydroxide solutions (8 M), or a mixture of alkaline hydroxide and alkaline silicate solution (NaOH-Na2SiO3 or KOH-K2SiO3). The results showed that OPFA can be used as an alkaline activator, showing mechanical properties slightly lower than those obtained when additional alkaline hydroxide activating solutions were used. The best compressive strength was obtained for geopolymers that use alkaline silicates as an activating solution. However, the best thermal insulation properties were obtained for control geopolymers. The microstructural characteristics of the geopolymers were evaluated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM-EDS) that corroborate the formation of geopolymeric gel in all the specimens, being the amount of gel formed greater in samples using commercial potassium activating solutions. These results demonstrate the feasibility of using this type of waste, OPFA, as activating reagents in the manufacture of geopolymers or alkaline activated materials. The manufactured geopolymers can be used as compressed earth blocks for walls and partitions, since the specimens pursue mechanical properties that comply with current regulations, presenting better thermal insulation properties. 


Mayo, 2021 | DOI: 10.1016/j.jmrt.2021.03.102

LED-driven controlled deposition of Ni onto TiO2 for visible-light expanded conversion of carbon dioxide into C-1-C-2 alkanes


Sanz-Marco, A; Hueso, JL; Sebastian, V; Nielsen, D; Mossin, S; Holgado, JP; Bueno-Alejo, CJ; Balas, F; Santamaria, J
Nanoscale Advances
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

ABSTRACT ▼

Photocatalytic gas-phase hydrogenation of CO2 into alkanes was achieved over TiO2-supported Ni nanoparticles under LED irradiation at 365 nm, 460 nm and white light. The photocatalysts were prepared using photo-assisted deposition of Ni salts under LED irradiation at 365 nm onto TiO2 P25 nanoparticles in methanol as a hole scavenger. This procedure yielded 2 nm Ni particles decorating the surface of TiO2 with a nickel mass content of about 2%. Before the photocatalytic runs, Ni/TiO2 was submitted to thermal reduction at 400 °C in a 10% H2 atmosphere which induced O-defective TiO2−x substrates. The formation of oxygen vacancies, Ti3+ centers and metallic Ni sites upon photocatalytic CO2 hydrogenation was confirmed by operando EPR analysis. In situ XPS under reaction conditions suggested a strong metal–support interaction and the co-existence of zero and divalent Ni states. These photoactive species enhanced the photo-assisted reduction of CO2 below 300 °C to yield CO, CH4 and C2H6 as final products.


Abril, 2021 | DOI: 10.1039/d1na00021g

Electrochromic response and porous structure of WO3 cathode layers


Louloudakis, D; Mouratis, K; Gil-Rostra, J; Koudoumas, E; Alvarez, R; Palmero, A; Gonzalez-Elipe, AR
Electrochimica Acta, 376 (2021) 138049
Nanotecnología en Superficies y Plasma

ABSTRACT ▼

Maximizing the electrochromic response of tungsten oxide-based systems demands highly porous electrode layers that facilitate the incorporation of electrolyte cations during the reduction process. In this work, amorphous and porous WO3 thin films were grown on indium tin dioxide glass substrates by magnetron sputtering at oblique angles at two different plasma gas pressures. Remarkably, the film that showed higher porosity presented a worse electrochromic response in terms of durability, time response and charge density capacity. This result is analyzed and explained on the basis of the features of the porous structure of the films: While the typical nanostructure developed at low pressures possesses large and connected pore voids with few ramifications, the nanostructure generated at a higher pressure presents a rather sponge-like porous structure with numerous and small well-connected voids. A general discussion on the role of the porous structure and, particularly, on the accessible pore volume and area is carried out. It is concluded that not only the accessible pore volume, defining the volume of electrolyte that stays inside the layer, but also the accessible pore area, which defines the efficiency of the incorporation/release of Li+ cations within the electrode material, determine the efficiency and reversibility of the electrochromic response.


Abril, 2021 | DOI: 10.1016/j.electacta.2021.138049

Cu supported Fe-SiO2 nanocomposites for reverse water gas shift reaction


Gonzalez-Castano, M; de Miguel, JCN; Sinha, F; Wabo, SG; Klepel, O; Arellano-Garcia, H
Journal of CO2 Utilization, 46 (2021) 101493
Química de Superficies y Catálisis

ABSTRACT ▼

This work analyses the catalytic activity displayed by Cu/SiO2, Cu-Fe/SiO2 and Cu/FSN (Fe-SiO2 nanocomposite) catalysts for the Reverse Water Gas Shift reaction. Compared to Cu/SiO2 catalyst, the presence of Fe resulted on higher CO?s selectivity and boosted resistances against the constitution of the deactivation carbonaceous species. Regarding the catalytic performance however, the extent of improvement attained through incorporation Fe species strongly relied on the catalysts' configuration. At 30 L/gh and H-2:CO2 ratios = 3, the performance of the catalysts? series increased according to the sequence: Cu/SiO2 < Cu-Fe/SiO2 << Cu/FSN. The remarkable catalytic enhancements provided by Fe-SiO2 nanocomposites under different RWGS reaction atmospheres were associated to enhanced catalyst surface basicity's and stronger Cu-support interactions. The catalytic promotion achieved by Fe-SiO2 nanocomposites argue an optimistic prospective for nanocomposite catalysts within future CO2-valorising technologies.


Abril, 2021 | DOI: 10.1016/j.jcou.2021.101493

Nanofibrous Matrix of Defined Composition Sustains Human Induced Pluripotent Stem Cell Culture


Borrego-Gonzalez, S; de la Cerda, B; Diaz-Corrales, FJ; Diaz-Cuenca, A
ACS Applied Bio Materials, 4 (2021) 3035-3040
Materiales para Bioingeniería y Regeneración Tisular

ABSTRACT ▼

Human induced pluripotent stem cells (hiPSCs) represent the most promising biological material for regenerative medicine applications. In this work, a 3D solid nanofibrous matrix of defined composition (Colamigel-S) consisting of 97 wt % gelatin, 2.6 wt % atelocollagen, and 0.4 wt % laminin has been reproducibly processed and characterized and exhibits a homogeneous nanofibrillar network of high surface area, interconnected microcavities, and typical D-periodic collagen fibril nanostructural features. The purpose of the study was to test the performance of Colamigel-S as substrate for in vitro hiPSCs culture, finding that these cells efficiently attach and grow keeping their characteristic stem morphology and undifferentiated state.


Abril, 2021 | DOI: 10.1021/acsabm.0c00425

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