26 results on '"Hermenegildo García"'
Search Results
2. Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO2 Hydrogenation
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Bogdan Jurca, Lu Peng, Ana Primo, Alvaro Gordillo, Amarajothi Dhakshinamoorthy, Vasile I. Parvulescu, and Hermenegildo García
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graphitic carbon ,CO2 methanation ,alloy nanoparticles ,Chemistry ,QD1-999 - Abstract
Starting from the reported activity of Co-Fe nanoparticles wrapped onto graphitic carbon (Co-Fe@C) as CO2 hydrogenation catalysts, the present article studies the influence of a series of metallic (Pd, Ce, Ca, Ca, and Ce) and non-metallic (S in various percentages and S and alkali metals) elements as Co-Fe@C promoters. Pd at 0.5 wt % somewhat enhances CO2 conversion and CH4 selectivity, probably due to H2 activation and spillover on Co-Fe. At similar concentrations, Ce does not influence CO2 conversion but does diminish CO selectivity. A 25 wt % Fe excess increases the Fe-Co particle size and has a detrimental effect due to this large particle size. The presence of 25 wt % of Ca increases the CO2 conversion and CH4 selectivity remarkably, the effect being attributable to the CO2 adsorption capacity and basicity of Ca. Sulfur at a concentration of 2.1% or higher acts as a strong poison, decreasing CO2 conversion and shifting selectivity to CO. The combination of S and alkali metals as promoters maintain the CO selectivity of S but notably increase the CO2 conversion. Overall, this study shows how promoters and poisons can alter the catalytic activity of Co/Fe@C catalysts, changing from CH4 to CO. It is expected that further modulation of the activity of Co/Fe@C catalysts can serve to drive the activity and selectivity of these materials to any CO2 hydrogenation products that are wanted.
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- 2022
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3. Turning Carbon Dioxide and Ethane into Ethanol by Solar-Driven Heterogeneous Photocatalysis over RuO2- and NiO-co-Doped SrTiO3
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Larissa O. Paulista, Josep Albero, Ramiro J. E. Martins, Rui A. R. Boaventura, Vítor J. P. Vilar, Tânia F. C. V. Silva, and Hermenegildo García
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heterogeneous thermo-photocatalysis ,solar fuels synthesis ,hybrid perovskite catalyst ,double doping approach ,CO2 photoconversion ,ethane upgrading ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
The current work focused on the sunlight-driven thermo-photocatalytic reduction of carbon dioxide (CO2), the primary greenhouse gas, by ethane (C2H6), the second most abundant element in shale gas, aiming at the generation of ethanol (EtOH), a renewable fuel. To promote this process, a hybrid catalyst was prepared and properly characterized, comprising of strontium titanate (SrTiO3) co-doped with ruthenium oxide (RuO2) and nickel oxide (NiO). The photocatalytic activity towards EtOH production was assessed in batch-mode and at gas-phase, under the influence of different conditions: (i) dopant loading; (ii) temperature; (iii) optical radiation wavelength; (vi) consecutive uses; and (v) electron scavenger addition. From the results here obtained, it was found that: (i) the functionalization of the SrTiO3 with RuO2 and NiO allows the visible light harvest and narrows the band gap energy (ca. 14–20%); (ii) the selectivity towards EtOH depends on the presence of Ni and irradiation; (iii) the catalyst photoresponse is mainly due to the visible photons; (iv) the photocatalyst loses > 50% efficiency right after the 2nd use; (v) the reaction mechanism is based on the photogenerated electron-hole pair charge separation; and (vi) a maximum yield of 64 μmol EtOH gcat−1 was obtained after 45-min (85 μmol EtOH gcat−1 h−1) of simulated solar irradiation (1000 W m−2) at 200 °C, using 0.4 g L−1 of SrTiO3:RuO2:NiO (0.8 wt.% Ru) with [CO2]:[C2H6] and [Ru]:[Ni] molar ratios of 1:3 and 1:1, respectively. Notwithstanding, despite its exploratory nature, this study offers an alternative route to solar fuels’ synthesis from the underutilized C2H6 and CO2.
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- 2021
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4. Vapor-Phase Photocatalytic Overall Water Splitting Using Hybrid Methylammonium Copper and Lead Perovskites
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Teresa García, Rocío García-Aboal, Josep Albero, Pedro Atienzar, and Hermenegildo García
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hybrid perovskite ,photocatalysis ,water splitting ,hydrogen production ,Chemistry ,QD1-999 - Abstract
Films or powders of hybrid methylammonium copper halide perovskite exhibit photocatalytic activity for overall water splitting in the vapor phase in the absence of any sacrificial agent, resulting in the generation of H2 and O2, reaching a maximum production rate of 6 μmol H2 × g cat−1h−1 efficiency. The photocatalytic activity depends on the composition, degreasing all inorganic Cs2CuCl2Br2 perovskite and other Cl/Br proportions in the methylammonium hybrids. XRD indicates that MA2CuCl2Br2 is stable under irradiation conditions in agreement with the linear H2 production with the irradiation time. Similar to copper analogue, hybrid methylammonium lead halide perovskites also promote the overall photocatalytic water splitting, but with four times less efficiency than the Cu analogues. The present results show that, although moisture is strongly detrimental to the photovoltaic applications of hybrid perovskites, it is still possible to use these materials as photocatalysts for processes requiring moisture due to the lack of relevance in the photocatalytic processes of interparticle charge migration.
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- 2020
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5. Alteration of the Mitochondrial Effects of Ceria Nanoparticles by Gold: An Approach for the Mitochondrial Modulation of Cells Based on Nanomedicine
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Patricia Gutiérrez-Carcedo, Sergio Navalón, Rafael Simó, Xavier Setoain, Carolina Aparicio-Gómez, Ibane Abasolo, Victor Manuel Victor, Hermenegildo García, and José Raúl Herance
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mitochondrial function ,ceria nanoparticles ,gold-supported ceria nanoparticles ,antioxidant ,triphenylphosphonium gold-supported ceria nanoparticles ,Chemistry ,QD1-999 - Abstract
Ceria nanoparticles are cell compatible antioxidants whose activity can be enhanced by gold deposition and by surface functionalization with positive triphenylphosphonium units to selectively target the mitochondria. The antioxidant properties of these nanoparticles can serve as the basis of a new strategy for the treatment of several disorders exhibiting oxidative stress, such as cancer, diabetes or Alzheimer’s disease. However, all of these pathologies require a specific antioxidant according with their mechanism to remove oxidant species excess in cells and diminish their effect on mitochondrial function. The mechanism through which ceria nanoparticles neutralize oxidative stress and their effect on mitochondrial function have not been characterized yet. In the present study, the mitochondria antioxidant effect of ceria and ceria-supported gold nanoparticles, with or without triphenylphosphonium functionalization, was assessed in HeLa cells. The effect caused by ceria nanoparticles on mitochondria function in terms of mitochondrial membrane potential (∆Ψm), adenosine triphosphate (ATP) production, nuclear respiratory factor 1 (NRF1) and nuclear factor erythroid–2–like 1 (NFE2L1) was reversed by the presence of gold. Furthermore, this effect was enhanced when nanoparticles were functionalized with triphenylphosphonium. Our study illustrates how the mitochondrial antioxidant effect induced by ceria nanoparticles can be modulated by the presence of gold.
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- 2020
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6. Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice
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Alejandra Rendón-Patiño, Antonio Domenech-Carbó, Ana Primo, and Hermenegildo García
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superlattice ,2d materials ,electrocatalytic ,Chemistry ,QD1-999 - Abstract
Evidence by selected area diffraction patterns shows the successful preparation of large area (cm × cm) MoS2/graphene heterojunctions in coincidence of the MoS2 and graphene hexagons (superlattice). The electrodes of MoS2/graphene in superlattice configuration show improved catalytic activity for H2 and O2 evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS2/graphene heterojunction with random stacking.
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- 2020
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7. Palladium Supported on Porous Chitosan–Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate
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Aicha Anouar, Nadia Katir, Abdelkrim El Kadib, Ana Primo, and Hermenegildo García
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liquid hydrogen carriers ,formate as hydrogen carrier ,catalyst for hydrogen generation ,palladium as catalyst for hydrogen generation ,chitosan–graphene oxide as catalyst support ,Organic chemistry ,QD241-441 - Abstract
Adsorption of Pd(NH3)42+ in preformed chitosan−graphene oxide (CS-GO) beads and their subsequent reduction with NaBH4 afford well-dispersed, high dispersion (~21%) of uniformly sized Pd nanoparticles (~1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by ammonium formate decomposition. The optimal GO proportion of 7 wt% allows reaching, at 60 °C, a turnover frequency above 2200 h−1—being outstanding among the highest values reported for this process to date. Interestingly, no formation of CO or CH4 was detected. The catalyst did not leach, although it underwent gradual deactivation, probably caused by the increase in the Pd average size that became over 3 nm after three uses. Our results are relevant in the context of efficient on-board hydrogen generation from liquid organic hydrogen carriers in transportation.
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- 2019
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8. Encapsulation of Metal Nanoparticles within Metal–Organic Frameworks for the Reduction of Nitro Compounds
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Sergio Navalón, Mercedes Álvaro, Amarajothi Dhakshinamoorthy, and Hermenegildo García
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metal–organic frameworks ,metal nanoparticles ,nitro compounds ,reduction reaction ,Organic chemistry ,QD241-441 - Abstract
Nitro group reduction is a reaction of a considerable importance for the preparation of bulk chemicals and in organic synthesis. There are reports in the literature showing that incorporation of metal nanoparticles (MNPs) inside metal−organic frameworks (MOFs) is a suitable strategy to develop catalysts for these reactions. Some of the examples reported in the literature have shown activity data confirming the superior performance of MNPs inside MOFs. In the present review, the existing literature reports have been grouped depending on whether these MNPs correspond to a single metal or they are alloys. The final section of this review summarizes the state of the art and forecasts future developments in the field.
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- 2019
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9. Quality Improvement of Few-Layers Defective Graphene from Biomass and Application for H2 Generation
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Jinbao He, Aicha Anouar, Ana Primo, and Hermenegildo García
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defective graphene ,chitosan pyrolysis ,alginate pyrolysis ,graphene from biomass ,Chemistry ,QD1-999 - Abstract
Pyrolysis of filmogenic natural polymers gives rise to the formation of films of few-layers defective, undoped, and doped graphenes with low electrical conductivity (3000 to 5000 Ω/sq). For the sake of valorization of biomass wastes, it would be of interest to decrease the density of structural defects in order to increase the conductivity of the resulting few-layers graphene samples. In the present study, analytical and spectroscopic evidence is provided showing that by performing the pyrolysis at the optimal temperature (1100 °C), under a low percentage of H2, a significant decrease in the density of defects related to the presence of residual oxygen can be achieved. This improvement in the quality of the resulting few-layers defective graphene is reflected in a decrease by a factor of about 3 or 5 for alginic acid and chitosan, respectively, of the electrical resistance. Under optimal conditions, few-layers defective graphene films with a resistance of 1000 Ω /sq were achieved. The electrode made of high-quality graphene prepared at 1100 °C under Ar/H2 achieved a H2 production of 3.62 µmol with a positive applied bias of 1.1 V under LED illumination for 16 h.
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- 2019
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10. Graphene-Based Materials as Efficient Photocatalysts for Water Splitting
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Josep Albero, Diego Mateo, and Hermenegildo García
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defective graphene ,photocatalysis ,solar fuels ,hydrogen generation ,facet-oriented nanoparticles ,Organic chemistry ,QD241-441 - Abstract
Photocatalysis has been proposed as one of the most promising approaches for solar fuel production. Among the photocatalysts studied for water splitting, graphene and related materials have recently emerged as attractive candidates due to their striking properties and sustainable production when obtained from biomass wastes. In most of the cases reported so far, graphene has been typically used as additive to enhance its photocatalytic activity of semiconductor materials as consequence of the improved charge separation and visible light harvesting. However, graphene-based materials have demonstrated also intrinsic photocatalytic activity towards solar fuels production, and more specifically for water splitting. The photocatalytic activity of graphene derives from defects generated during synthesis or their introduction through post-synthetic treatments. In this short review, we aim to summarize the most representative examples of graphene based photocatalysts and the different approaches carried out in order to improve the photocatalytic activity towards water splitting. It will be presented that the introduction of defects in the graphenic lattice as well as the incorporation of small amounts of metal or metal oxide nanoparticles on the graphene surface improve the photocatalytic activity of graphene. What is more, a simple one-step preparation method has demonstrated to provide crystal orientation to the nanoparticles strongly grafted on graphene resulting in remarkable photocatalytic properties. These two features, crystal orientation and strong grafting, have been identified as a general methodology to further enhance the photocatalytic activity in graphenebased materials for water splitting. Finally, future prospects in this filed will be also commented.
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- 2019
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11. Polystyrene as Graphene Film and 3D Graphene Sponge Precursor
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Alejandra Rendón-Patiño, Jinan Niu, Antonio Doménech-Carbó, Hermenegildo García, and Ana Primo
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graphene ,polystyrene ,3D graphene sponges ,electrochemistry ,Chemistry ,QD1-999 - Abstract
Polystyrene as a thin film on arbitrary substrates or pellets form defective graphene/graphitic films or powders that can be dispersed in water and organic solvents. The materials were characterized by visible absorption, Raman and X-ray photoelectron spectroscopy, electron and atomic force microscopy, and electrochemistry. Raman spectra of these materials showed the presence of the expected 2D, G, and D peaks at 2750, 1590, and 1350 cm−1, respectively. The relative intensity of the G versus the D peak was taken as a quantitative indicator of the density of defects in the G layer.
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- 2019
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12. Carbon Nanohorns Modified with Conjugated Terthienyl/Terthiophene Structures: Additives to Enhance the Performance of Dye-Sensitized Solar Cells
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Daniel Iglesias, Pedro Atienzar, Ester Vázquez, María Antonia Herrero, and Hermenegildo García
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carbon nanohorns ,dye-sensitized solar cells ,terthienyl dyes ,terthienylphenylene vinylene dyes ,Chemistry ,QD1-999 - Abstract
A series of carbon nanohorns (CNHs) constituted by the aggregation of about 2000 individual conical graphene tubes (diameters from 2 nm to 5 nm and a length of 40–50 nm) that have been modified with dyes of two, three, or four terthienyl groups has been prepared by adsorbing the corresponding dye on the CNH. Persistent inks in o-dichlorobenzene (o-DCB) of these dye-CNH conjugates were obtained by laser irradiation of o-DCB suspensions of the dye-CNH solids. These inks were used in combination or not with N719 dye for the preparation of dye-sensitized solar cells (DSSC) of TiO2. It was measured that the terthienyl dye with the largest conjugation deposited on the CNH additively increased the performance of an analogous TiO2 cell from an efficiency of 4.07% to 6.24%. This result shows the potential of dye-modified CNHs as additives in the construction of more efficient DSSCs.
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- 2017
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13. Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice
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Ana Primo, Hermenegildo García, Antonio Doménech-Carbó, Alejandra Rendón-Patiño, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), and Generalitat Valenciana
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Materials science ,business.industry ,Graphene ,General Chemical Engineering ,Superlattice ,2d materials ,Stacking ,Heterojunction ,Overpotential ,Electrocatalytic ,law.invention ,lcsh:Chemistry ,QUIMICA ORGANICA ,lcsh:QD1-999 ,law ,Electrode ,biological sciences ,health occupations ,Water splitting ,Optoelectronics ,bacteria ,General Materials Science ,Selected area diffraction ,business - Abstract
[EN] Evidence by selected area diffraction patterns shows the successful preparation of large area (cm x cm) MoS2/graphene heterojunctions in coincidence of the MoS2 and graphene hexagons (superlattice). The electrodes of MoS2/graphene in superlattice configuration show improved catalytic activity for H-2 and O-2 evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS2/graphene heterojunction with random stacking., This research was funded by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-68653-CO2-R1) and Generalitat Valenciana (Prometeo 2017-083).
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- 2020
14. Vapor-Phase Photocatalytic Overall Water Splitting Using Hybrid Methylammonium Copper and Lead Perovskites
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Rocío García-Aboal, Pedro Atienzar, Josep Albero, Hermenegildo García, Teresa García, and Ministerio de Economía y Competitividad (España)
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Materials science ,hydrogen production ,General Chemical Engineering ,hybrid perovskite ,Halide ,chemistry.chemical_element ,02 engineering and technology ,Methylammonium lead halide ,010402 general chemistry ,01 natural sciences ,water splitting ,Article ,lcsh:Chemistry ,chemistry.chemical_compound ,QUIMICA ORGANICA ,General Materials Science ,Hybrid perovskite ,Photocatalysis ,Water splitting ,Perovskite (structure) ,Hydrogen production ,021001 nanoscience & nanotechnology ,Copper ,0104 chemical sciences ,chemistry ,Chemical engineering ,lcsh:QD1-999 ,0210 nano-technology ,photocatalysis ,Photocatalytic water splitting - Abstract
Films or powders of hybrid methylammonium copper halide perovskite exhibit photocatalytic activity for overall water splitting in the vapor phase in the absence of any sacrificial agent, resulting in the generation of H2 and O2, reaching a maximum production rate of 6 &mu, mol H2 ×, g cat&minus, 1h&minus, 1 efficiency. The photocatalytic activity depends on the composition, degreasing all inorganic Cs2CuCl2Br2 perovskite and other Cl/Br proportions in the methylammonium hybrids. XRD indicates that MA2CuCl2Br2 is stable under irradiation conditions in agreement with the linear H2 production with the irradiation time. Similar to copper analogue, hybrid methylammonium lead halide perovskites also promote the overall photocatalytic water splitting, but with four times less efficiency than the Cu analogues. The present results show that, although moisture is strongly detrimental to the photovoltaic applications of hybrid perovskites, it is still possible to use these materials as photocatalysts for processes requiring moisture due to the lack of relevance in the photocatalytic processes of interparticle charge migration.
- Published
- 2020
15. Influence of the Polarity of the Electric Field on Electrorheometry
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Samir H. Sadek, Francisco J. Galindo-Rosales, J. Hermenegildo García-Ortiz, and Ingeniería Mecánica y Diseño Industrial
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Materials science ,Polarity (physics) ,Rheometer ,02 engineering and technology ,01 natural sciences ,Electrorheological fluid ,Electric field ,electrorheology ,0103 physical sciences ,Newtonian fluid ,General Materials Science ,Instrumentation ,Complex fluid ,Fluid Flow and Transfer Processes ,capillary breakup extensional electrorheometry (CaBEER) ,010304 chemical physics ,Process Chemistry and Technology ,General Engineering ,Mechanics ,extensional flow ,021001 nanoscience & nanotechnology ,Breakup ,Computer Science Applications ,Simple shear ,dielectric liquid bridge ,0210 nano-technology - Abstract
Uniaxial extensional flow is a canonical flow typically used in rheological characterization to provide complementary information to that obtained by imposing simple shear flow. In spite of the importance of having a full rheological characterization of complex fluids, publications on the rheological characterization of mobile liquids under extensional flow have increased significantly only in the last 20 years. In the case of the rheological characterization of electrorheological fluids, the situation is even more dramatic, as the ERFs have been exclusively determined under simple shear flow, where an electrorheological cell is attached to the rotational rheometer generating an electric field perpendicular to the flow direction and that does not allow for inverting the polarity. The very recent work published by Sadek et al., who developed a new electrorheological cell to be used with the commercial Capillary Breakup Extensional Rheometer (CaBER), allows for the very first time performing electrorheometry under extensional flow. By means of the same experimental setup, this study investigates the influence of the polarity of the imposed electric field on the filament thinning process of a Newtonian and an electrorheological fluid. Results show that a polarity against the gravity results in filament thinning processes that live longer or reach a stable configuration at lower intensities of the applied electric field.
- Published
- 2019
16. Nanometric Cu-ZnO Particles Supported on N-Doped Graphitic Carbon as Catalysts for the Selective CO2 Hydrogenation to Methanol
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Lu Peng, Bogdan Jurca, Alberto Garcia-Baldovi, Liang Tian, German Sastre, Ana Primo, Vasile Parvulescu, Amarajothi Dhakshinamoorthy, and Hermenegildo Garcia
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heterogeneous catalysis ,CO2 hydrogenation ,N-doped graphene ,methanol synthesis ,Chemistry ,QD1-999 - Abstract
The quest for efficient catalysts based on abundant elements that can promote the selective CO2 hydrogenation to green methanol still continues. Most of the reported catalysts are based on Cu/ZnO supported in inorganic oxides, with not much progress with respect to the benchmark Cu/ZnO/Al2O3 catalyst. The use of carbon supports for Cu/ZnO particles is much less explored in spite of the favorable strong metal support interaction that these doped carbons can establish. This manuscript reports the preparation of a series of Cu-ZnO@(N)C samples consisting of Cu/ZnO particles embedded within a N-doped graphitic carbon with a wide range of Cu/Zn atomic ratio. The preparation procedure relies on the transformation of chitosan, a biomass waste, into N-doped graphitic carbon by pyrolysis, which establishes a strong interaction with Cu nanoparticles (NPs) formed simultaneously by Cu2+ salt reduction during the graphitization. Zn2+ ions are subsequently added to the Cu–graphene material by impregnation. All the Cu/ZnO@(N)C samples promote methanol formation in the CO2 hydrogenation at temperatures from 200 to 300 °C, with the temperature increasing CO2 conversion and decreasing methanol selectivity. The best performing Cu-ZnO@(N)C sample achieves at 300 °C a CO2 conversion of 23% and a methanol selectivity of 21% that is among the highest reported, particularly for a carbon-based support. DFT calculations indicate the role of pyridinic N doping atoms stabilizing the Cu/ZnO NPs and supporting the formate pathway as the most likely reaction mechanism.
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- 2024
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17. Quality Improvement of Few-Layers Defective Graphene from Biomass and Application for H2 Generation
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Hermenegildo García, Jinbao He, Aicha Anouar, Ana Primo, Ministerio de Economía y Competitividad (España), Generalitat Valenciana, and Ministerio de Ciencia, Innovación y Universidades (España)
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Materials science ,General Chemical Engineering ,Conductivity ,Article ,defective graphene ,law.invention ,lcsh:Chemistry ,chemistry.chemical_compound ,Defective graphene ,QUIMICA ORGANICA ,Graphene from biomass ,Electrical resistance and conductance ,Electrical resistivity and conductivity ,law ,graphene from biomass ,Alginate pyrolysis ,General Materials Science ,chitosan pyrolysis ,Alginic acid ,Graphene ,Doping ,alginate pyrolysis ,lcsh:QD1-999 ,chemistry ,Chemical engineering ,Electrode ,Chitosan pyrolysis ,Pyrolysis - Abstract
Pyrolysis of filmogenic natural polymers gives rise to the formation of films of few-layers defective, undoped, and doped graphenes with low electrical conductivity (3000 to 5000 Ω/sq). For the sake of valorization of biomass wastes, it would be of interest to decrease the density of structural defects in order to increase the conductivity of the resulting few-layers graphene samples. In the present study, analytical and spectroscopic evidence is provided showing that by performing the pyrolysis at the optimal temperature (1100 °, C), under a low percentage of H2, a significant decrease in the density of defects related to the presence of residual oxygen can be achieved. This improvement in the quality of the resulting few-layers defective graphene is reflected in a decrease by a factor of about 3 or 5 for alginic acid and chitosan, respectively, of the electrical resistance. Under optimal conditions, few-layers defective graphene films with a resistance of 1000 Ω /sq were achieved. The electrode made of high-quality graphene prepared at 1100 °, C under Ar/H2 achieved a H2 production of 3.62 µ, mol with a positive applied bias of 1.1 V under LED illumination for 16 h.
- Published
- 2019
18. Gold Nanoparticles Supported on Ceria Nanoparticles Modulate Leukocyte–Endothelium Cell Interactions and Inflammation in Type 2 Diabetes
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Pedro Díaz-Pozo, Francisco Canet, Abdessamad Grirrane, Sandra Lopez-Domenech, José Raul Herance, Nadezda Apostolova, Clara Luna-Marco, Susana Rovira-Llopis, Miguel Marti, Carlos Morillas, Milagros Rocha, Hermenegildo Garcia, and Victor M. Victor
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gold-ceria nanoparticle ,ROS ,diabetes ,inflammation ,atherosclerosis ,Therapeutics. Pharmacology ,RM1-950 - Abstract
Gold-ceria nanoparticles (Au/CeO2) are known to have antioxidant properties. However, whether these nanoparticles can provide benefits in type 2 diabetes mellitus (T2D) remains unknown. This work aimed to study the effects of Au/CeO2 nanoparticles at different rates of gold purity (10, 4.4, 1.79 and 0.82) on leukocyte–endothelium interactions and inflammation in T2D patients. Anthropometric and metabolic parameters, leukocyte–endothelium interactions, ROS production and NF-κB expression were assessed in 57 T2D patients and 51 healthy subjects. T2D patients displayed higher Body Mass Index (BMI) and characteristic alterations in carbohydrate and lipid metabolism. ROS production was increased in leukocytes of T2D patients and decreased by Au/CeO2 at 0.82% gold. Interestingly, Au/CeO2 0.82% modulated leukocyte–endothelium interactions (the first step in the atherosclerotic process) by increasing leukocyte rolling velocity and decreasing rolling flux and adhesion in T2D. A static adhesion assay also revealed diminished leukocyte–endothelium interactions by Au/CeO2 0.82% treatment. NF-κB (p65) levels increased in T2D patients and were reduced by Au/CeO2 treatment. Cell proliferation, viability, and apoptosis assays demonstrated no toxicity produced by Au/CeO2 nanoparticles. These results demonstrate that Au/CeO2 nanoparticles at 0.82% exert antioxidant and anti-inflammatory actions in the leukocyte–endothelium interaction of T2D patients, suggesting a protective role against the appearance of atherosclerosis and cardiovascular diseases when this condition exists.
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- 2022
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19. Phosphorus-Rich Ruthenium Phosphide Embedded on a 3D Porous Dual-Doped Graphitic Carbon for Hydrogen Evolution Reaction
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Aicha Anouar, Antonio Doménech-Carbó, and Hermenegildo Garcia
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ruthenium electrocatalysts ,metal phosphides ,ruthenium diphosphide ,dual-doped graphitic carbon ,hydrogen evolution reaction ,Chemistry ,QD1-999 - Abstract
Metal phosphides have recently emerged as promising electrocatalysts for hydrogen evolution reaction (HER). Herein, we report the synthesis of ruthenium diphosphide embedded on a dual-doped graphitic carbon by pyrolyzing chitosan beads impregnated with ruthenium chloride and phosphorus pentoxide. The as-synthesized RuP2@N-P-C displays a good electrocatalytic activity in acidic, neutral and alkaline media. We show that the HER activity of the electrocatalyst can be tuned by varying the concentration of Li+ cations. Co-diffusion effects on H+ exerted by Li+ on HER in the porous carbon matrix have been observed.
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- 2022
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20. Graphitic Carbon Nitride as Visible-Light Photocatalyst Boosting Ozonation in Wastewater Treatment
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Amarajothi Dhakshinamoorthy, Antón López-Francés, Sergio Navalon, and Hermenegildo Garcia
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carbon nitride ,organic pollutants ,ozone ,photocatalysis ,visible light ,Chemistry ,QD1-999 - Abstract
Light can boost ozone efficiency in advanced oxidation processes (AOPs), either by direct ozone photolysis with UV light or by using a photocatalyst that can be excited with UV-Vis or solar light. The present review summarizes literature data on the combination of ozone and the g-C3N4 photocatalyst for the degradation of probe molecules in water, including oxalic, p-hydroxybenzoic and oxamic acids as well as ciprofloxacin and parabens. g-C3N4 is a metal-free visible-light photocatalyst based on abundant elements that establishes a synergistic effect with ozone, the efficiency of the combination of the photocatalysis and ozonation being higher than the sum of the two treatments independently. Available data indicate that this synergy derives from the higher efficiency in the generation of hydroxyl radicals due to the efficient electron quenching by O3 of photogenerated conduction band electrons in the g-C3N4 photocatalyst. Given the wide use of ozonizers in water treatment, it is proposed that their implementation with g-C3N4 photocatalysis could also boost ozone efficiency in the AOPs of real waste waters.
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- 2022
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21. α,β-Enone Borylation by Bis(Pinacolato)Diboron Catalyzed by Cu3(BTC)2 Using Cesium Carbonate as a Base
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Amarajothi Dhakshinamoorthy, Mercedes Alvaro, Abdullah M. Asiri, and Hermenegildo Garcia
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borylation ,2-cyclohexenone ,heterogeneous catalysis ,metal organic frameworks ,Chemistry ,QD1-999 - Abstract
Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) as a heterogeneous catalyst in the presence of cesium carbonate as a base is reported for the borylation of α,β-conjugated enones by bis(pinacolato)diboron (B2pin2). According to the hot-filtration test, Cu3(BTC)2 is acting as a heterogeneous catalyst. Further, Cu3(BTC)2 exhibits a wide substrate scope and can be reused in consecutive runs, maintaining a crystal structure as evidenced by powder X-ray diffraction (XRD). A suitable mechanism is also proposed for this transformation using Cu3(BTC)2 as catalyst.
- Published
- 2021
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22. Cobalt-Based Metal Organic Frameworks as Solids Catalysts for Oxidation Reactions
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Amarajothi Dhakshinamoorthy, Eva Montero Lanzuela, Sergio Navalon, and Hermenegildo Garcia
- Subjects
cobalt ,aerobic oxidation ,metal-organic frameworks ,heterogeneous catalysis ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Metal organic frameworks (MOFs) are porous crystalline solids whose frameworks are constituted by metal ions/nodes with rigid organic linkers leading to the formation of materials having high surface area and pore volume. One of the unique features of MOFs is the presence of coordinatively unsaturated metal sites in their crystalline lattice that can act as Lewis acid sites promoting organic transformations, including aerobic oxidation reactions of various substrates such as hydrocarbons, alcohols, and sulfides. This review article summarizes the existing Co-based MOFs for oxidation reactions organized according to the nature of substrates like hydrocarbon, alcohol, olefin, and water. Both aerobic conditions and peroxide oxidants are discussed. Emphasis is placed on comparing the advantages of using MOFs as solid catalysts with respect to homogeneous salts in terms of product selectivity and long-term stability. The final section provides our view on future developments in this field.
- Published
- 2021
- Full Text
- View/download PDF
23. Polyvinylidene Fluoride-Graphene Oxide Membranes for Dye Removal under Visible Light Irradiation
- Author
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Sabri Alyarnezhad, Tiziana Marino, Jalal Basiri Parsa, Francesco Galiano, Claudia Ursino, Hermenegildo Garcìa, Marta Puche, and Alberto Figoli
- Subjects
PVDF-GO membranes ,photocatalytic membranes ,triethyl phosphate ,GO nanosheets ,dye removal ,photocatalysis ,Organic chemistry ,QD241-441 - Abstract
In this study, polyvinylidene fluoride (PVDF)-graphene oxide (GO) membranes were obtained by employing triethyl phosphate (TEP) as a solvent. GO nanosheets were prepared and characterized in terms of scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), chemical analysis and inductively coupled plasma mass spectroscopy (ICP). Two different phase inversion techniques, Non-Solvent Induced Phase Separation (NIPS) and Vapour-Induced Phase Separation (VIPS)/NIPS, were applied to study the effect of fabrication procedure on the membrane structure and properties. Membranes were characterized by SEM, AFM, pore size, porosity, contact angle and mechanical tests, and finally tested for photocatalytic methylene blue (MB+) degradation under visible light irradiation. The effect of different pH values of dye aqueous solutions on the photocatalytic efficiency was investigated. Finally, the influence of NaCl salt on the MB+ photodegradation process was also evaluated.
- Published
- 2020
- Full Text
- View/download PDF
24. Solar Light Photocatalytic CO2 Reduction: General Considerations and Selected Bench-Mark Photocatalysts
- Author
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Ștefan Neațu, Juan Antonio Maciá-Agulló, and Hermenegildo Garcia
- Subjects
photocatalytic CO2 reduction ,solar fuels ,heterogeneous photocatalysis ,renewable energy ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
The reduction of carbon dioxide to useful chemicals has received a great deal of attention as an alternative to the depletion of fossil resources without altering the atmospheric CO2 balance. As the chemical reduction of CO2 is energetically uphill due to its remarkable thermodynamic stability, this process requires a significant transfer of energy. Achievements in the fields of photocatalysis during the last decade sparked increased interest in the possibility of using sunlight to reduce CO2. In this review we discuss some general features associated with the photocatalytic reduction of CO2 for the production of solar fuels, with considerations to be taken into account of the photocatalyst design, of the limitations arising from the lack of visible light response of titania, of the use of co-catalysts to overcome this shortcoming, together with several strategies that have been applied to enhance the photocatalytic efficiency of CO2 reduction. The aim is not to provide an exhaustive review of the area, but to present general aspects to be considered, and then to outline which are currently the most efficient photocatalytic systems.
- Published
- 2014
- Full Text
- View/download PDF
25. One-Step Preparation of Large Area Films of Oriented MoS2 Nanoparticles on Multilayer Graphene and Its Electrocatalytic Activity for Hydrogen Evolution
- Author
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Jinbao He, Cristina Fernández, Ana Primo, and Hermenegildo Garcia
- Subjects
molybdenum disulfide ,oriented nanoparticles ,multilayer graphene films ,hydrogen evolution ,electrocatalyst ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
MoS2 is a promising material to replace Pt-based catalysts for the hydrogen evolution reaction (HER), due to its excellent stability and high activity. In this work, MoS2 nanoparticles supported on graphitic carbon (about 20 nm) with a preferential 002 facet orientation have been prepared by pyrolysis of alginic acid films on quartz containing adsorbed (NH4)2MoS4 at 900 °C under Ar atmosphere. Although some variation of the electrocatalytic activity has been observed from batch to batch, the MoS2 sample exhibited activity for HER (a potential onset between 0.2 and 0.3 V vs. SCE), depending on the concentrations of (NH4)2MoS4 precursor used in the preparation process. The loading and particle size of MoS2, which correlate with the amount of exposed active sites in the sample, are the main factors influencing the electrocatalytic activity.
- Published
- 2018
- Full Text
- View/download PDF
26. Numerical Investigation of Dimensionless Parameters in Carangiform Fish Swimming Hydrodynamics
- Author
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Marianela Machuca Macías, José Hermenegildo García-Ortiz, Taygoara Felamingo Oliveira, and Antonio Cesar Pinho Brasil Junior
- Subjects
swimming fish ,quasi-propulsive efficiency ,Reynolds number ,Strouhal number ,slip number ,leading-edge vortex ,Technology - Abstract
Research into how fish and other aquatic organisms propel themselves offers valuable natural references for enhancing technology related to underwater devices like vehicles, propellers, and biomimetic robotics. Additionally, such research provides insights into fish evolution and ecological dynamics. This work carried out a numerical investigation of the most relevant dimensionless parameters in a fish swimming environment (Reynolds Re, Strouhal St, and Slip numbers) to provide valuable knowledge in terms of biomechanics behavior. Thus, a three-dimensional numerical study of the fish-like lambari, a BCF swimmer with carangiform kinematics, was conducted using the URANS approach with the k-ω-SST transition turbulence closure model in the OpenFOAM software. In this study, we initially reported the equilibrium Strouhal number, which is represented by St∗, and its dependence on the Reynolds number, denoted as Re. This was performed following a power–law relationship of St∝Re(−α). We also conducted a comprehensive analysis of the hydrodynamic forces and the effect of body undulation in fish on the production of swimming drag and thrust. Additionally, we computed propulsive and quasi-propulsive efficiencies, as well as examined the influence of the Reynolds number and Slip number on fish performance. Finally, we performed a vortex dynamics analysis, in which different wake configurations were revealed under variations of the dimensionless parameters St, Re, and Slip. Furthermore, we explored the relationship between the generation of a leading-edge vortex via the caudal fin and the peak thrust production within the motion cycle.
- Published
- 2024
- Full Text
- View/download PDF
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