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2022


Electrocatalytic CO2 conversion to C-2 products: Catalysts design, market perspectives and techno-economic aspects


Ruiz-López, E; Gandara-Loe, J; Baena-Moreno, F; Reina, TR; Odriozola, JA
Renewable & Sustainable Energy Reviews, 161 (2022) 112329

ABSTRACT

The energy crisis caused by the incessant growth in global energy demand joint to its associated greenhouse emissions motivates the urgent need to control and mitigate atmospheric CO2 levels. Leveraging CO2 as carbon pool to produce value-added products represents a cornerstone of the circular economy. Among the CO2 utilization strategies, electrochemical reduction of CO2 conversion to produce fuels and chemicals is booming due to its versatility and end-product flexibility. Herein most of the studies focused on C-1 products although C-2 and C2+ compounds are chemically and economically more appealing targets requiring advanced catalytic materials. Still, despite the complex pathways for C2+ products formation, their multiple and assorted applications have motivated the search of suitable electrocatalysts. In this review, we gather and analyse in a comprehensive manner the progress made regarding C2+ products considering not only the catalyst design and the electrochemistry features but also techno-economic aspects in order to envisage the most profitable scenarios. This state-of-the-art analysis showcases that electrochemical reduction of CO2 to C-2 products will play a key role in the decarbonisation of the chemical industry paving the way towards a low-carbon future.


June, 2022 | DOI: 10.1016/j.rser.2022.112329

Enhanced photocatalytic activity of TiO2/WO3 nanocomposite from sonochemical-microwave assisted synthesis for the photodegradation of ciprofloxacin and oxytetracycline antibiotics under UV and sunlight


Moghni, N; Boutoumi, H; Khalaf, H; Makaoui, N; Colon, G
Journal of Photochemistry and Photobiology A-Chemistry, 428 (2022) 113848

ABSTRACT

The TiO2/WO3 photocatalysts were prepared by a simple assisted sonochemical -microwave combination. The wide surface and structural characterization of synthesized material confirmed that the adopted preparation method resulted in nanoparticulated crystallite anatase phase of TiO2 with a large surface area (> 200 m(2)/g), and the dispersion of WO3 on the surface of TiO2. The photoactivity was assessed for the photodegradation of ciprofloxacin (CIP) and oxytetracycline (OTC) antibiotics under UV and sunlight irradiation. The mineralization rate, toxicity assessment, pollutant concentration effect on photodegradation efficiency, and reusability potential under sunlight were all investigated. Results showed that TiO2 doped with 5 wt% of WO3 exhibited the best photocatalytic activity under UV (100% degradation) and solar light. Rate constants for CIP and OTC degradation showed that TiO2/WO3 significantly improved with respect to bare TiO2. The antibacterial study revealed that the photodegraded solutions became less toxic than the initial CIP and OTC solutions showing a significant decrease in the inhibition zone diameter and mineralization rates. The prepared TiO2/WO3 maintained high performances in the presence of high concentrations of pollutants as well as good stability after four consecutive uses. The increased photocatalytic activity is attributed to the incorporation of WO3, which extends the light absorption range and decreases the rate of electron -hole recombination.


June, 2022 | DOI: 10.1016/j.jphotochem.2022.113848

Design of Full-Temperature-Range RWGS Catalysts: Impact of Alkali Promoters on Ni/CeO2


Gandara-Loe, J; Zhang, Q; Villora-Pico, JJ; Sepulveda-Escribano, A; Pastor-Perez, L; Reina, TR
Energy & Fuels, 36 (2022) 6362-6373

ABSTRACT

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.


June, 2022 | DOI: 10.1021/acs.energyfuels.2c00784

Evidence of new Ni-O-K catalytic sites with superior stability for methane dry reforming


Azancot, L; Blay, V; Blay-Roger, R; Bobadilla, LF; Penkova, A; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 307 (2022) 121148

ABSTRACT

Liquid fuels produced via Fischer-Tropsch synthesis from biomass-derived syngas constitute an attractive and sustainable energy vector for the transportation sector. This study focuses on the role of potassium as a promoter in Ni-based catalysts for reducing coke deposition during catalytic dry reforming. The study provides a new structural link between catalytic performance and physicochemical properties. We identify new Ni-O-K chemical states associated with high stability in the reforming process, evidenced by different characterization techniques. The nickel particles form a core surrounded by a Ni-O-K phase layer (Ni@Ni-O-K) during the reduction of the catalyst. This phase likely presents an alkali-nickelate-type structure, in which nickel is stabilized in oxidation state + 3. The Ni-O-K formation induces essential changes in the electronic, physical, structural, and morphological properties of the catalysts, notably enhancing their long-term stability in dry reforming. This work thus provides new directions for designing more efficient catalysts for sustainable gas-to-liquids processes.


June, 2022 | DOI: 10.1016/j.apcatb.2022.121148

Reduction of N2O with hydrosilanes catalysed by RuSNS nanoparticles


Molinillo, P; Lacroix, B; Vattier, F; Rendon, N; Suarez, A; Lara, P
Chemical Communications

ABSTRACT

A series of RuSNS nanoparticles, prepared by decomposition of Ru(COD)(COT) with H-2 in the presence of an SNS ligand, have been found to catalyse the reduction of the greenhouse gas N2O to N-2 employing different hydrosilanes.


June, 2022 | DOI: 10.1039/d2cc01470j

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, (2022) 5023-5035

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.


June, 2022 | DOI: 10.1007/s10973-021-10940-x

Effect of Spatial Inhomogeneity on Quantum Trapping br


Esteso, V; Carretero-Palacios, S; Miguez, H
Journal of Physical Chemistry Letters, 13 (2022) 4513-4519

ABSTRACT

An object that is immersed in afluid and approaching a substrate mayfind apotential energy minimum at a certain distance due to the balance between attractive and repulsiveCasimir-Lifshitz forces, a phenomenon referred to as quantum trapping. This equilibriumdepends on the relative values of the dielectric functions of the materials involved. Herein, westudy quantum trapping effects in planar nanocomposite materials and demonstrate that they arestrongly dependent on the characteristics of the spatial inhomogeneity. As a model case, weconsider spherical particles embedded in an otherwise homogeneous material. We propose aneffective medium approximation that accounts for the effect of inclusions andfind that anunprecedented and counterintuitive intense repulsive Casimir-Lifshitz force arises as a result ofthe strong optical scattering and absorption size-dependent resonances caused by their presence. Our results imply that the properanalysis of quantum trapping effects requires comprehensive knowledge and a detailed description of the potential inhomogeneity(caused by imperfections, pores, inclusions, and density variations) present in the materials involved


June, 2022 | DOI: 10.1021/acs.jpclett.2c00807

Electron beam evaporated vs. magnetron sputtered nanocolumnar porous stainless steel: Corrosion resistance, wetting behavior and anti-bacterial activity


Bobaru, S; Rico-Gavira, V; Garcia-Valenzuela, A; Lopez-Santos, C; Gonzalez-Elipe, AR
Materials Today Communications, 31 (2022) 103266

ABSTRACT

Stainless steel (SS), widely used because of its outstanding corrosion protection properties, does not possess any particular anti-stain or anti-bacterial activity as required for household and sanitary applications. This work reports the fabrication of SS thin films that, keeping a similar corrosion resistance than the bulk material, presents hydrophobicity and anti-bacterial activity. These thin films are prepared at ambient temperature by physical vapor deposition (PVD), either electron beam evaporation (EBE) or magnetron sputtering (MS), at oblique angles (OAD). According to their scanning electron microcopy and atomic force microscopy analysis, the microstructure of the OAD-SS thin films consisted of tilted and separated nanocolumns defining a surface topology that, characterized by a high percentage of void space, varied with the deposition conditions and procedure, either EBE or MS. It has been shown that particularly the nanocolumnar MS-OAD thin films preserved and even improved the high corrosion resistance of compact SS, as determined by electrochemical analysis. Besides, all OAD-SS thin films depict hydrophobicity and a high antibacterial activity. These features, particularly remarkable for the MS-OAD thin films, have been related with their tip-like termination at the surface and the existence of large void spaces separating the nanocolumns. This topology appears to affect negatively the bacteria's deployment onto the surface and therefore the survival rate. Differences in the corrosion and antibacterial performance between EBE and MS-OAD thin films have been related with the specificities of these two PVD methods of thin film preparation. A relatively high abrasion resistance, as determined by abrasion tests, supports the use of MS-OAD thin films for the protection of commodity materials.


June, 2022 | DOI: 10.1016/j.mtcomm.2022.103266

Characterization of Re-Mo/ZSM-5 catalysts: How Re improves the performance of Mo in the methane dehydroaromatization reaction


Lopez-Martin, A; Sini, MF; Cutrufello, MG; Caballero, A; Colon, G
Applied Catalysis B-Environmental, 304 (2022) 120960

ABSTRACT

In this study, the promoting effect of rhenium addition as a co-dopant on Mo/ZSM-5 catalysts system has been analysed. Hence, bimetallic (Re-Mo/ZSM-5) catalysts have been synthesized using a sequential impregnation methodology. The catalytic performance for direct aromatization of methane reaction has been determined and correlated with their physical and chemical state combining multiple characterization techniques. An important synergy between Mo and Re, affected by the sequential impregnation, has been observed. Thus, Re1-Mo4/ZSM-5 in which Re has been incorporated first shows notably higher aromatic yields and stability against deactivation. Characterization results suggest that catalytic enhancement is due to the important effect of Re presence in close interaction with Mo. Improved evolution of ethane through C-C coupling would be correlated to this catalytic performance. As we discuss, Mo nature and location in the bimetallic systems are strongly conditioned by Re and the impregnation sequence and favours such intermediate step.


May, 2022 | DOI: 10.1016/j.apcatb.2021.120960

Synthesis and characterization of alkali-activated materials containing biomass fly ash and metakaolin: effect of the soluble salt content of the residue


Jurado-Contreras, S; Bonet-Martínez, E; Sánchez-Soto, PJ; Gencel, O; Eliche-Quesada, D
Archives of Civil and Mechanical Engineering, 22 (2022) 121

ABSTRACT

The present study investigates the production and characterization of alkali-activated bricks prepared with mixing metakaolin (MK) and biomass fly ash from the combustion of a mix of pine pruning, forest residues and energy crops (BFA). To use this low cost and high availability waste, different specimens were prepared by mixing MK with different proportions of BFA (25, 50 and 75 wt%). Specimens containing only metakaolin and biomass fly ash were produced for the purpose of comparison. Effects of the alkali content of biomass fly ash, after a washing pretreatment (WBFA), as well as the concentration of NaOH solution on the physical, mechanical and microstructural properties of the alkali-activated bricks were studied. It was observed that up to 50 wt% addition of the residue increases compressive strength of alkali-activated bricks. Alkalinity and soluble salts in fly ash have a positive effect, leading materials with the improved mechanical properties. Concentration of NaOH 8 M or higher is required to obtain optimum mechanical properties. The compressive strength increases from 23.0 MPa for the control bricks to 44.0 and 37.2 MPa with the addition of 50 wt% BFA and WBFA, respectively, indicating an increase of more than 60%. Therefore, the use of biomass fly ash provides additional alkali (K) sources that could improve the dissolution of MK resulting in high polycondensation. However, to obtain optimum mechanical properties, the amount of BFA cannot be above 50 wt%.


May, 2022 | DOI: 10.1007/s43452-022-00444-2

Versatile Ni-Ru catalysts for gas phase CO2 conversion: Bringing closer dry reforming, reverse water gas shift and methanation to enable end-products flexibility


Merkouri, LP; le Sache, E; Pastor-Perez, L; Duyar, MS; Reina, TR
Fuel, 315 (2022) 123097

ABSTRACT

Advanced catalytic materials able to catalyse more than one reaction efficiently are needed within the CO2 utilisation schemes to benefit from end-products flexibility. In this study, the combination of Ni and Ru (15 and 1 wt%, respectively) was tested in three reactions, i.e. dry reforming of methane (DRM), reverse water-gas shift (RWGS) and CO2 methanation. A stability experiment with one cycle of CO2 methanation-RWGS-DRM was carried out. Outstanding stability was revealed for the CO2 hydrogenation reactions and as regards the DRM, coke formation started after 10 h on stream. Overall, this research showcases that a multicomponent Ni-Ru/CeO2 -Al2O3 catalyst is an unprecedent versatile system for gas phase CO2 recycling. Beyond its excellent performance, our switchable catalyst allows a fine control of end-products selectivity.


May, 2022 | DOI: 10.1016/j.fuel.2021.123097

Neodymium doped lanthanide fluoride nanoparticles as contrast agents for luminescent bioimaging and X-ray computed tomography


Gonzalez-Mancebo, D; Becerro, AI; Calderon-Olvera, RM; Cantelar, E; Corral, A; Balcerzyk, M; De la Fuente, JM; Ocaña, M
Boletin de la Sociedad Española de Ceramica y Vidrio, 61 (2022) 540-549

ABSTRACT

The synthesis of uniform neodymium-doped lanthanum trifluoride nanoparticles with lenticular shape and a mean diameter around 45 nm by using a homogeneous precipitation method is reported. The luminescent properties of the synthesized samples in terms of their emission spectra and emission lifetime are analyzed as a function of the Nd content to find the optimum phosphor and its suitability for luminescent imaging in the second biological window. The X-ray attenuation properties of the optimum phosphor are evaluated to investigate their additional ability as contrast agent for X-ray computed tomography. Finally, the colloidal stability of the obtained nanoparticles in physiological medium and their cytotoxicity are also analyzed to assess their aptness for in vivo bioimaging applications. 


May, 2022 | DOI: 10.1016/j.bsecv.2021.07.004

Effect of sintering under CO+N-2/H-2 and CO2+air atmospheres on the physicochemical features of a commercial nano-YSZ


Colomer, M.T.; Simenas, M.; Banys, J.; Vattier, F.; Gagor, A.; Maczka, M.
Journal of Alloys and Compounds, 904 (2022) 163976

ABSTRACT

Given the need to process anodes and composites based on nano-YSZ in reducing or in air containing additional CO2 atmospheres for the fabrication of solid oxide fuel cells (SOFCs), and solid oxide electrolysis cells (SOECs), we have studied the effect of the exposure to CO+N2/H2 or CO2+air mixtures during sintering of YSZ green pellets, prepared from commercial nanopowders, on their structure, microstructure, chemical composition and their electrical properties. The reduced sample shows Raman bands at 1298 and 1605 cm−1 that are assigned to the D and G bands of carbon, respectively. The bands intensity ratio ID/IG indicates a larger content of disordered carbon. X-ray photoelectron spectroscopy (XPS) shows that C is present in the reduced samples as reduced carbon. However, the samples sintered in CO2+air present C as carbonate-type. Impedance spectroscopy reveals that the highest total conductivity is for the reduced samples in the whole range of studied temperatures. In addition, sintering in CO2+air causes a detrimental effect on the grain boundary conductivity and therefore, on the total electrical conductivity of YSZ. It can be due to the presence of impurities such as carbonates and oxidised or even, polymerised carbonaceous species located at those areas.


May, 2022 | DOI: 10.1016/j.jallcom.2022.163976

High temperature mechanical properties of polycrystalline Y2SiO5


Cabezas-Rodríguez, R; Ciria, D; Martínez-Fernandez, J; Dezanneau, G; Karolak, F; Ramirez-Rico, J
Boletin de la Sociedad Española de Ceramica y Vidrio, 61 (2022) S60-S68-228

ABSTRACT

The high temperature mechanical properties of polycrystalline Y2SiO5 were studied in compression at temperatures in the range of 1200-1400 degrees C, both in constant strain rate and constant stress experiments. To examine the effect of grain size on the plastic deformation, two routes were used for the synthesis and sintering of Y2SiO5: one of solid state reaction followed by conventional sintering in air, and one of sol-gel synthesis followed by spark-plasma sintering, resulting in starting grain sizes of 2.2 and 0.9 mu m, respectively. Ceramics obtained by these routes exhibited different high-temperature compression behavior: while the conventionally processed ceramic exhibited grain growth during mechanical testing and a stress exponent close to one, compatible with diffusional creep, the spark-plasma sintered ceramic showed no grain growth but significant cavitation, a stress exponent close to two and partially superplastic behavior. These results have implications for the design and lifetime assessment of rare earth silicate-based environmental barrier coatings. 


May, 2022 | DOI: 10.1016/j.bsecv.2021.09.008

Role of Surface Topography in the Superhydrophobic Effect-Experimental and Numerical Studies


Ibrahim, SH; Wejrzanowski, T; Przybyszewski, B; Kozera, R; Garcia-Casas, X; Barranco, A
Materials, 15 (2022) 3112

ABSTRACT

Within these studies, the effect of surface topography for hydrophobic coatings was studied both numerically and experimentally. Chemically modified polyurethane coating was patterned by application of a laser beam. A set of patterns with variously distant linear peaks and grooves was obtained. The cross section of the pattern showed that the edges of the peaks and grooves were not sharp, instead forming a rounded, rectangle-like shape. For such surfaces, experimental studies were performed, and in particular the static contact angle (SCA), contact angle hysteresis (CAH), and roll-off angle (ROA) were measured. Profilometry was used to create a numerical representation of the surface. Finite volume method was then applied to simulate the behavior of the water droplets. The model developed herewith enabled us to reproduce the experimental results with good accuracy. Based on the verified model, the calculation was extended to study the behavior of the water droplet on the simulated patterns, both spiked and rectangular. These two cases, despite a similar SCA of the water droplet, have shown extremely different ROA. Thus, more detailed studies were dedicated to other geometrical features of such topography, such as the size and distance of the surface elements. Based on the results obtained herewith, the future design of superhydrophobic and/or icephobic topography is discussed.


May, 2022 | DOI: 10.3390/ma15093112

The SrCO3/SrO system for thermochemical energy storage at ultra-high temperature


Amghar, N; Ortiz, C; Perejon, A; Valverde, JM; Maqueda, LP; Jimenez, PES
Solar Energy Materials and Solar Cells, 238 (2022) 111632

ABSTRACT

Thermochemical energy storage (TCES) has attracted interest in the last years due to the possibility of attaining high energy densities, seasonal storage capacity and greater efficiencies than currently commercial thermal energy storage systems using molten salts. This work analyses the potential of an ultra-high temperature TCES system based on the SrCO3/SrO system. The process relies upon the reversible decomposition of SrCO3 into SrO and CO2. As proposed in previous works for the integration of the Ca-Looping process to store energy in CSP plants, both the calcination (endothermic) and carbonation (exothermic) reactions are carried out in a closed CO2 loop. At these conditions, the required temperature to attain full calcination in short residence times is around 1400 degrees C whereas carbonation takes place at about 1200 degrees C. Using this process, the energy density potentially achievable by the storage material is very high (around 2000 MJ/m(3)) while the ultra-high carbonation temperature would improve thermoelectric efficiency. The enhancement of the multicycle performance of the SrCO3/SrO system using refractory additives is also explored. Even though current commercial CSP plants with tower technology cannot yet operate at these ultra-high temperatures, recent advances in the development of high-temperature solar receivers could allow operation at 1400 degrees C in the medium term. Finally, a conceptual model of the integration of the SrCO3/SrO system in a CSP plant supports higher overall efficiency and energy density, but lower solar-to-electric efficiency due to thermal losses.


May, 2022 | DOI: 10.1016/j.solmat.2022.111632

Analysis of the effect of cationic ratio Bi3+/Fe3+ on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method


Palomino-Resendiz, RL; Bolarin-Miro, AM; Pedro-Garcia, F; Sanchez-De Jesus, F; Espinos-Manzorro, JP; Cortes-Escobes-Escobedo, CA
Ceramics International, 48 (2022) 14746-14753

ABSTRACT

This study examined the effects of the cationic ratio of Bi3+/Fe3+ via X-ray photoelectron spectroscopy (XPS) on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method. X-ray diffraction revealed the successful synthesis of single-phase BiFeO3 powder after annealing the sonicated material at 723 K. The powder was composed of agglomerates of rounded particles with a mean particle size of 35 nm. XPS was performed to determine the Bi3+/Fe3+ ratio as a function of the heat treatment process and its relationship with secondary phases, which can modulate the magnetic properties of the nano powders. The cationic ratio obtained by XPS confirmed that the powders obtained at 623 and 923 K have excess Bi3+ and Fe3+, respectively, which induces the formation of Bi24Fe2O39 and Bi2Fe4O9 as the majority phases. Powder annealing at 723 K revealed a ferromagnetic order with specific magnetization of 1.8 Am-2/kg. This ferromagnetic behavior was preserved after applying spark plasma sintering (SPS) at 923 K. By contrast, conventional sintering at 1023 K promotes antiferromagnetic order. In addition, the dielectric properties of the ceramic material of the sintered powders showed a behavior related to a typical ferroelectric material.


May, 2022 | DOI: 10.1016/j.ceramint.2022.02.011

Insights into the structural and physicochemical properties of Zn-Bi-O composites for efficient photodegradation of caffeic acid, rhodamine B and methyl orange


F.Puga; J.A.Navío; J.M.Córdoba; F.Romero-Sarria; M.C.Hidalgo
Applied Surface Science, 581 (2022) 152351

ABSTRACT

Different Zn-Bi-O composites were synthesized following the starting chemical molar composition of ZnBi2O4 spinels by a sol–gel method, (ZnBiO)-SG, and its subsequent hydrothermal treatment, (ZnBiO)-HT. The acquired X-ray diffractograms after sequential thermal treatments at a programmed rate indicate that both precursors evolved, after calcination at 500 °C, to materials (ZnBiO) with different stoichiometry. The use of different characterization techniques (both FT-IR and TEM), allowed us to establish that, with the sol–gel process a mixed ZnO/Bi2O3 oxide is generated, while after hydrothermal process a ternary Zn-Bi-O oxide is formed, with small amounts of residual ZnO. The photocatalytic properties of the synthesized samples were evaluated using Caffeic acid, Rhodamine B and Methyl Orange as model substrates. It can be concluded that both catalysts showed excellent photocatalytic activity for the degradation of trans-caffeic acid under both UV and visible illumination. The leaching process (in particular of zinc), which is produced with the illumination time (in particular under UV illumination) in the presence of oxygen, raises the hypothesis of a foreseeable formation of complexes (photochemically stable or unstable) of caffeic acid with Zn2+ and Bi3+ ions. The plausible donor/acceptor interactions between the toxic molecules studied and the Zn2+ and Bi3+ ions, could condition the degradation processes, by means of a photoassisted process that would take place both, in the heterogeneous (photocatalytic) and homogeneous (photoassisted) phases. For the degradation processes of Rhodamine B and Methyl Orange, additional experimental conditions are studied that significantly improved their photocatalytic degradation.


April, 2022 | DOI: 10.1016/j.apsusc.2021.152351

Ionomer-Free Nickel-Iron bimetallic electrodes for efficient anion exchange membrane water electrolysis


Lopez-Fernandez, E; Gomez-Sacedon, C; Gil-Rostra, J; Espinos, JP; Gonzalez-Elipe, AR; Yubero, F; De Lucas-Consuegra, A
Chemical Engineering Journal, 433 (2022) 133774

ABSTRACT

A bottleneck for the deployment of the Anion Exchange Membrane Water Electrolysis (AEMWE) is the manufacturing of efficient and long lasting anodes and cathodes for the cells. Highly performant bimetallic Ni/Fe catalyst films with various atomic ratios have been prepared by magnetron sputtering in an oblique angle configuration (MS-OAD) and used as anodes for AEMWE. Electrocatalytic experiments in a small three-electrode cell and a thorough analysis of the electrode properties with various physico-chemical characterization tech-niques have been used to select the nanostructured anode catalyst which, depicting an optimized Ni/Fe ratio, presents the maximum activity for the oxygen evolution reaction. These anode layers are then scale-up for their integration in an AEMWE cell where the influence of assembly conditions and the effect of adding an ionomer to the anodes have been studied. The obtained results have demonstrated the outstanding properties of the fabri-cated bimetallic films in terms of activity, stability, and operation under ionomer-free conditions. Current density values around 400 and 600 mA cm(-2) at 40??& nbsp;and 60 C (2.0 V), respectively, much higher than those obtained with pure Ni, were obtained with an optimized membrane electrode assembly. The high yield obtained with these electrodes gains further relevance when considering that the current yield per unit mass of the anodic active phase catalyst (i.e., 1086 mA mg(-1) at 2.0 V and 40??) is the highest among equivalent values reported in literature. The possibilities and prospects of the use of bimetallic catalyst films prepared by MS-OAD for AEMWE are discussed.


April, 2022 | DOI: 10.1016/j.cej.2021.133774

Enhanced up-conversion photoluminescence in fluoride-oxyfluoride nanophosphor films by embedding gold nanoparticles


Ngo, TT; Lozano, G; Miguez, H
Materials Advances (2022)

ABSTRACT

Owing to their unique non-linear optical character, lanthanide-based up-converting materials are potentially interesting for a wide variety of fields ranging from biomedicine to light harvesting. However, their poor luminescent efficiency challenges the development of technological applications. In this context, localized surface plasmon resonances (LSPRs) have been demonstrated as a valuable strategy to improve light conversion. Herein, we utilize LSPR induced by gold nanoparticles (NPs) to enhance up-conversion photoluminescence (UCPL) in transparent, i.e. scattering-free, films made of nanophosphors formed by fluoride–oxyfluoride host matrix that feature high thermal stability. Transparency allows excitation by an external source without extinction losses caused by unwanted diffuse reflection. We provide a simple method to embed gold NPs in films made of YF/YOF:Yb3+,Er3+ UC nanophosphors, via preparation of a viscous paste composed of both UC nanophosphors and colloidal gold NPs, reducing complexity in sample fabrication. The dimensions of gold NPs are such that their associated LSPR matches spectrally with the green emission band of the Er3+ doped nanophosphors. In order to demonstrate the benefits of plasmonic nanoparticles for UCPL in nanophosphor films, we provide a careful analysis of the structural properties of the composite thin films along with precise characterization of the impact of the gold NPs on the photophysical properties of UC nanophosphors.


April, 2022 | DOI: 10.1039/D2MA00068G

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