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2021


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

Dehydration of glucose to 5-Hydroxymethlyfurfural on bifunctional carbon catalysts


Bounoukta, CE; Megias-Sayago, C; Ammari, F; Ivanova, S; Monzon, A; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 286 (2021) 119938
Química de Superficies y Catálisis

ABSTRACT

The proposed study tries to reply on one important question concerning glucose dehydration: What is the role of bare or tandem Lewis/Bronsted acid sites in the reaction and which are better? A series of mono and bifunctional catalyst are designed and screened for the glucose dehydration reaction. The results clearly reveal that catalyst activity is a function of catalyst composition. The presence of Lewis sites the reaction toward first step isomerization, while the Brunsted acid dehydrate directly glucose to HMF via levoglucosane intermediate. This study proposed also a kinetic modelling of the included reactions and their contrast with the empirical observations.


Junio, 2021 | DOI: 10.1016/j.apcatb.2021.119938

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

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
Materiales Ópticos Multifuncionales - Tribología y Protección de Superficies

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

Fructose dehydration reaction over functionalized nanographitic catalysts in MIBK/H2O biphasic system


Martin, GD; Bounoukta, CE; Ammari, F; Dominguez, MI; Monzon, A; Ivanova, S; Centeno, MA
Catalysis Today, 366 (2021) 68-76
Química de Superficies y Catálisis

ABSTRACT

A series of functionalized nanographitic carbons is prepared, characterized and tested in fructose dehydration reaction to 5-hydroxymethylfurfural. The functionalization treatment was selected to introduce various Bro?nsted acid sites and to modify the textural and catalytic properties of the initial carbon material. Within the series, the sulfonated carbons present the most interesting catalytic behavior resulting in important selectivity to the desired product once the reaction variables were properly adjusted.


Abril, 2021 | DOI: 10.1016/j.cattod.2020.03.016

Enhancing the electrical conductivity of in-situ reduced graphene oxide-zirconia composites through the control of the processing routine


Lopez-Pernia, C; Morales-Rodriguez, A; Gallardo-Lopez, A; Poyato, R
Ceramics International, 47 (2021) 9382-9391
Reactividad de Sólidos

ABSTRACT

Graphene oxide (GO) was mixed with 3 mol% yttria tetragonal zirconia polycrystal (3YTZP) using two powder processing routines: a colloidal method in an aqueous solution and a combination of ultrasonication with highenergy planetary ball milling in wet conditions. Highly densified 3YTZP composites with reduced GO (rGO) were consolidated by Spark Plasma Sintering. The in-situ reduction of GO was successfully achieved during the high temperature sintering process and a detailed study of the restoration of the graphene structure in the sintered composites has been made by Raman spectroscopy. Although no differences between the composites prepared by the two processing methods were found in the distribution of the rGO throughout the 3YTZP matrix for high rGO contents (i.e. the composites with 5 and 10 vol% rGO), a better distribution of the graphene phase was found in the composites with 1 and 2.5 vol% rGO prepared by planetary ball milling. This result, together with a better reduction of the GO in these composites, led to the obtaining of rGO/3YTZP composites with a better behavior in terms of electrical conductivity: an electrical percolation threshold below 2.5 vol% rGO and a high electrical conductivity value (-610 S/m for 10 vol% rGO).


Abril, 2021 | DOI: 10.1016/j.ceramint.2020.12.069

Organophilization of acid and thermal treated sepiolite for its application in BTEX adsorption from aqueous solutions


Varela, CF; Pazos, MC; Alba, MD
Journal of Water Process Engineering, 40 (2021) 101949
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

Acid and thermal treated sepiolite was organophilized by cationic exchange with several alkylammonium cations (octylammonium, hexadecylammonium, tetradecyltrimethylammonium, and hexadecyltrimethylammonium). The adsorption capacity of BTEX from aqueous solutions was evaluated through the adsorption isotherms performed in batch. The results were analysed using three isotherm models: Freundlich, Langmuir and Dubinin-Radushkevich (D-R model). The behaviour of adsorption isotherm suggested the multilayer coverage on a heterogeneous surface, which is according to the Freundlich isotherm model. The thermodynamic analyse using the D-R model show that physical mechanisms govern the process. The maximum adsorption capacity of BTEX on the obtained materials was in the range values of 81.19 mg g(-1) - 1448.42 mg g(-)(1), which are higher than those reported up to now. The organo-sepiolite materials exhibit a high potential in the adsorption of BTEX compounds from aqueous solutions.


Abril, 2021 | DOI: 10.1016/j.jwpe.2021.101949

Novel procedure for studying laser-surface material interactions during scanning laser ablation cleaning processes on Cu-based alloys


Di Francia, E; Lahoz, R; Neff, D; Rico, V; Nuns, N; Angelini, E; Grassini, S
Applied Surface Science, 544 (2021) art. 178820
Nanotecnología en Superficies y Plasma

ABSTRACT

Laser ablation is an effective method to clean Cu-based alloys. A novel procedure of characterisation was developed involving O-18 isotopes evaluated by ToF-SIMS spectroscopy to assess the driving mechanisms of laser-surface interactions. The presence of re-oxidised compounds was detected, discerning between the oxygen from the corrosion layer and the one introduced by the interaction with the laser (that was generated in a controlled atmosphere of O-18 diluted in N-2). A set of samples treated with different laser conditions were characterised by FESEM and mu Raman. The results have shown that re-oxidation phenomenon can occur and its selectivity depends on the laser conditions.


Abril, 2021 | DOI: 10.1016/j.apsusc.2020.148820

Fluorinated and platinized Titania for Glycerol oxidation


Murcia, J.J.; Bautista, E; Ávila Martínez, E.G.; Rangel R.N.; Romero, R.; Cubillos Lobo, J.A.; Rojas Sarmiento, H.A.; Hernández, J.S.; Cárdenas, O.; Hidalgo, M.C.; Navío, J.A.; Baeza, R.
Materials Proceedings, 4 (2021) 37
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

In this research, photocatalysts based on TiO2 modified by fluorination and platinum addition were evaluated in the glycerol oxidation. These materials were characterized by different instrumental analysis techniques to determine the physicochemical properties. It was found that the surface modification lead to improve the materials absorption in the Visible region of the electromagnetic spectra and to increase the surface area of TiO2. By HPLC analysis was possible to observed that the photocatalysts 0.5% Pt-F-TiO2 showed the highest yield and selectivity towards glyceraldehyde (GAL). It was also observed that the increase in the platinum content until values of 2% had a negative effect in the effectiveness of fluorinated Titania in the glycerol photo-oxidation. The fluorination and platinum addition modify some physicochemical properties of TiO2, leading also to modify the reaction mechanism and selectivity during glycerol partial photo-oxidation and the dose of photocatalysts is an important reaction condition to obtain GAL and Dyhidroxyacetone (DHA) with yields above to 70%.


Abril, 2021 | DOI: 10.3390/IOCN2020-07792

Holmium phosphate nanoparticles as negative contrast agents for high-field magnetic resonance imaging: Synthesis, magnetic relaxivity study and in vivo evaluation


Gomez-Gonzalez, E; Caro, C; Martinez-Gutierrez, D; Garcia-Martin, ML; Ocana, M; Becerro, AI
Journal of Colloid and Interface Science, 587 (2021) 131-140
Materiales Coloidales

ABSTRACT

The increasing use of high magnetic fields in magnetic resonance imaging (MRI) scanners demands new contrast agents, since those used in low field instruments are not effective at high fields. In this paper, we report the synthesis of a negative MRI contrast agent consisting of HoPO4 nanoparticles (NPs). Three different sizes (27 nm, 48 nm and 80 nm) of cube-shaped NPs were obtained by homogeneous precipitation in polyol medium and then coated with poly(acrylic) acid (PAA) to obtain stable colloidal suspensions of HoPO4@PAA NPs in physiological medium (PBS). The transverse relaxivity (r2) of aqueous suspensions of the resulting NPs was evaluated at both 1.44 T and 9.4 T. A positive correlation between r2 values and field strength as well as between r2 values and particle size at both magnetic field strengths was found although this correlation failed for the biggest NPs at 9.4 T, likely due to certain particles aggregation inside the magnet. The highest r2 value (489.91 mM-1s−1) was found for the 48 nm NPs at 9.4 T. Toxicity studies demonstrated that the latter NPs exhibited low toxicity to living systems. Finally, in vivo studies demonstrated that HoPO4@PAA NPs could be a great platform for next-generation T2-weighted MRI contrast agents at high magnetic field.


Abril, 2021 | DOI: 10.1016/j.jcis.2020.11.119

Pb2+, Cd2+ and Hg2+ removal by designed functionalized swelling high-charged micas


Osuna, FJ; Pavon, E; Alba, MD
Science of The Total Environment, 764 (2021) 142811
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

The increasing accumulation of toxic heavy metals in the environment has generated the need of efficient removal systems, being the adsorption method the most popular one applied in aqueous solutions. Of particular concern is the case of Pb2+, Cd2+ and Hg2+ due to their high potential hazard. In this paper, we describe the feasibility of a new family of nanomaterials, swelling high charge micas, in the removal of these cations from aqueous solutions. Batch adsorption experiments were carried out in the as-made micas, NaMn, and after functionalization with ethylammonium, EA-Mn, and mercaptoethylammonium, MEA-Mn. The results have demonstrated that all of them are efficient heavy metal adsorbents, being Na-M2 the best adsorbent for Pb2+ and Cd2+, and, MEA-M2 for Hg2+.


Abril, 2021 | DOI: 10.1016/j.scitotenv.2020.142811

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

Zr and Fe on Pt/CeO2-MOx/Al2O3 catalysts for WGS reaction


Gonzalez-Castano, M; Ivanova, S; Centeno, MA; Ioanides, T; Arellano-Garcia, H; Odriozola, JA
International Journal of Hydrogen Energy, (2021)
Química de Superficies y Catálisis

ABSTRACT

By evaluating the functional modifications induced by Zr and Fe as dopants in Pt/CeO2‐MOx/Al2O3 catalysts (M = Fe and Zr), the key features for improving water gas shift (WGS) performance for these systems have been addressed. Pt/ceria intrinsic WGS activity is often related to improved H2 surface dynamics, H2O absorption, retentions and dissociation capacities which are influenced greatly by the support nature. Two metals, iron and zirconia, were chosen as ceria dopants in this work, either in separate manner or combined. Iron incorporation resulted in CO‐redox properties and oxygen storage capacities (OSC) improvement but the formation of Ce‐Fe solid solutions did not offer any catalytic benefit, while the Zr incorporation influenced in a great manner surface electron densities and shows higher catalytic activity. When combined both metals showed an important synergy evidenced by 30% higher CO conversions and attributed to greater surface electron densities population and therefore absorption and activity. This work demonstrates that for Pt/ceria catalysts OSC enhancement does not necessarily imply a catalytic promotion.


Marzo, 2021 | DOI: 10.1002/er.6646

The Complex Interplay of Lead Halide Perovskites with Their Surroundings


Galisteo-Lopez, JF; Calvo, ME; Miguez, H
Advanced Optical Materials, (2021) 2100133
Materiales Ópticos Multifuncionales

ABSTRACT

Photoexcitation of lead halide perovskites induces a restructuration of the material that simultaneously enhances its emission properties and triggers its degradation. These concomitant processes are strongly dependent on the surroundings of the perovskite, both while and after being processed, underlining the relevance the environment and the interfacial design have in the stability and performance of these materials and the devices based on them. This shocking observation reveals that when subjected to external illumination, lead halide perovskites undergo a number of photophysical processes that strongly modify their structure and thus their optoelectronic properties. Such photoinduced instability stems from a defective structure directly linked to the low-temperature and solution-processed fabrication routes generally employed to build perovskite solar cells with efficiencies comparable to state-of-the-art values. On the other hand, these same inexpensive and unsophisticated procedures make this material a promising component in energy conversion devices. Here, an analysis is provided regarding the different impact on the perovskite structure, hence on its optoelectronic performance, that the interaction with its surroundings has, providing specific examples that highlight this interplay, describing the kind of modification it induces, and listing the related effects on the optoelectronic properties that should be accounted for when characterizing them.


Marzo, 2021 | DOI: 10.1002/adom.202100133

Persistent luminescence of transparent ZnGa2O4:Cr3+ thin films from colloidal nanoparticles of tunable size dagger


Arroyo, E; Medran, B; Castaing, V; Lozano, G; Ocana, M; Becerro, AI
Journal of Materials Chemistry C, (2021)
Materiales Coloidales - Materiales Ópticos Multifuncionales

ABSTRACT

We report on the fabrication of ZnGa2O4:Cr3+ transparent thin films and the evaluation, for the first time in the literature, of their persistent red to NIR emission. For this purpose, we have used a simple and economic global strategy based on wet processing methods from colloidal nanospheres with uniform size. A microwave-assisted hydrothermal method was first developed for the synthesis of precursor particles, which allows size tuning from 300 nm to 30 nm through simple modification of the Zn2+ precursor and the Cr3+ content of the starting solutions. ZnGa2O4:Cr3+ transparent thin films over quartz substrates were then easily fabricated by spin coating, and their structural and optical characteristics were analyzed in detail after annealing at high temperature to elucidate the effect of processing temperature and particle size on the properties of the films. Indeed, our results indicate that high temperature annealing does not compromise the transparency of the films but improves their photoluminescence. In addition, the analysis reveals that persistence luminescence in our films is rather independent of the size of the precursor nanoparticles. Due to their transparency and persistent emission properties, films fabricated from colloidal suspensions of ZnGa2O4:Cr3+ nanoparticles show great potential for application in the fields of chemical sensing, information storage, labelling, and anti-counterfeiting technology.


Marzo, 2021 | DOI: 10.1039/d1tc00258a

Facile synthesis and characterization of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate nanocomposite for highly efficient removal of hazardous hexavalent chromium ions from water


Abdelghani Hsini, Yassine Naciri, Mohamed Benafqir, Zeeshan Ajmal, Nouh Aarab, Mohamed Laabd, J.A. Navío, F. Puga, Rabah Boukherroub, Bahcine Bakiz, Abdallah Albourine
Journal of Colloid and Interface Science, 585 (2021) 560-573
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

The present study describes the preparation of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate (BTCA-PANI@ZnP) nanocomposite via a facile two-step procedure. Thereafter, the as-prepared composite material adsorption characteristics for Cr(VI) ions removal were evaluated under batch adsorption. Kinetic approach studies for Cr(VI) removal, clearly demonstrated that the results of the adsorption process followed the pseudo second order and Langmuir models. The thermodynamic study indicated a spontaneous and endothermic process. Furthermore, higher monolayer adsorption was determined to be 933.88 mg g1 . In addition, the capability study regarding Cr(VI) ions adsorption over BTCA-PANI@ZnP nanocomposite clearly revealed that our method is suitable for large scale application. X-ray photoelectron spectroscopy (XPS) analysis confirmed Cr(VI) adsorption on the BTCA-PANI@ZnP surface, followed by its subsequent reduction to Cr(III). Thus, the occurrence of external mass transfer, electrostatic attraction and reduction phenomenon were considered as main mechanistic pathways of Cr(VI) ions removal. The superior adsorption performance of the material, the multidimensional characteristics of the surface and the involvement of multiple removal mechanisms clearly demonstrated the potential applicability of the BTCA-PANI@ZnP material as an effective alternative for the removal of Cr(VI) ions from wastewater.


Marzo, 2021 | DOI: 10.1016/j.jcis.2020.10.036

Solid-State Dewetting of Gold on Stochastically Periodic SiO2 Nanocolumns Prepared by Oblique Angle Deposition


Oliva-Ramirez, M; Wang, D; Flock, D; Rico, V; Gonzalez-Elipe, AR; Schaaf, P
ACS Applied Materials & Interfaces, 13 (2021) 11385-11395
Nanotecnología en Superficies y Plasma

ABSTRACT

Solid-state dewetting (SSD) on patterned substrates is a straightforward method for fabricating ordered arrays of metallic nanoparticles on surfaces. However, a drawback of this procedure is that the patterning of substrates usually requires time-consuming and expensive two-dimensional (2D) fabrication methods. Nanostructured thin films deposited by oblique angle deposition (OAD) present at the surface a form of stochastically arranged periodic bundles of nanocolumns that might act as a patterned template for fabricating arrays of nanoparticles by SSD. In this work, we explore this concept and investigate the effect of three different types of OAD SiO2 thin films on the SSD of Au deposited on their surface. We demonstrate that the size and spatial distribution of the particles can be tailored through the surface morphology of these OAD film substrates. It has been found that the SSD of the evaporated Au layer gives rise to a bimodal size distribution of particles. A majority of them appeared as mesoparticles with sizes.100 nm and the rest as nanoparticles with similar to 10 nm, respectively, located either on top of the nanocolumns following their lateral distribution (i.e., resulting from a patterning effect) or incorporated inside the open mesopores existing among them. Moreover, on the SiO2-OAD thin films where interconnected nanocolumnar bundles arrange in the form of discrete motifs, the patterning effect gave rise to the formation of approximately one Au mesoparticle per motif, which is one of the assets of patterned SSD. The morphological, optical (i.e., plasmon resonance), and crystalline structural characteristics of Au mesoparticles suggest that the interplay between a discontinuous nanocolumnar surface acting as a template and the poor adhesion of Au onto SiO2 are key factors for the observed template effect controlling the SSD on the surface of OAD thin films.


Marzo, 2021 | DOI: 10.1021/acsami.0c19327

Functionalized biochars as supports for Pd/C catalysts for efficient hydrogen production from formic acid


Santos, JL; Megias-Sayago, C; Ivanova, S; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 282 (2021) 119615
Química de Superficies y Catálisis

ABSTRACT

Biomass waste product was used to generate biochars as catalytic supports for selective hydrogen production from formic acid. The supports were obtained after pyrolysis in CO2 atmosphere of non-pretreated and che-mically ZnCl2 activated raw materials (vine shoot and crystalline cellulose). The support series includes materials with different textural properties and surface chemistry. The support nature and especially textural properties firstly affects significantly Pd size and dispersion and its interaction with the support and secondly influence in a great extent the catalytic behavior of the final material. The presence of prevailing mesoporous character appeared to be the most important parameter influencing formic acid dehydrogenation and overall hydrogen production.


Marzo, 2021 | DOI: 10.1016/j.apcatb.2020.119615

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