Artículos SCI
2022
2022
Materiales de Diseño para la Energía y Medioambiente
Iron-catalyzed graphitization for the synthesis of nanostructured graphitic carbons
Hunter, RD; Ramirez-Rico, J; Schnepp, ZJournal of Materials Chemistry A, 10 (2022) 4489-4516
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![](https://icms.us-csic.es/sites/icms.us-csic.es/files/Ram-1.png)
Carbons are versatile and diverse materials that have numerous applications across energy and environmental sciences. Carbons with a graphitic structure are particularly appealing due to their high chemical stability, large surface areas and high thermal and electronic conductivity. Numerous methods exist to produce nanostructured graphitic carbons but some of these can be energy-intensive and/or have problems with scalability. One option that is being increasingly explored is the process of iron-catalyzed graphitization. This simply involves the pyrolysis of carbon-rich precursors in the presence of an iron catalyst and has been used to produce carbons with a wide range of structures and properties. This review will examine the current field of iron-catalyzed graphitization, with a focus on molecular organic or biomass precursors. Bio-derived precursors are particularly attractive as a potential option for sustainable production of graphitic carbons. We start with a brief introduction to some key carbon structures, the current applications in which they are employed and some of the key methods that have been developed to produce nanostructured graphitic carbons. We will then review the history of catalytic graphitization before evaluating the wide range of conditions and precursors that have been employed in catalytic graphitization. Finally, this review will investigate the current challenges facing iron-catalyzed graphitization, looking particularly at the limitations of the current understanding of the mechanistic aspects of graphitization, with a view to outlining where research in this field might progress.
Febrero, 2022 | DOI: 10.1039/d1ta09654k
Nanotecnología en Superficies y Plasma
Plasma assisted CO2 dissociation in pure and gas mixture streams with a ferroelectric packed-bed reactor in ambient conditions
Navascues, P; Cotrino, J; Gonzalez-Elipe, AR; Gomez-Ramirez, AChemical Engineering Journal, 430 (2022) 133066
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![](https://icms.us-csic.es/sites/icms.us-csic.es/files/1-s2_334.png)
Carbon dioxide decomposition is a challenging target to combat climate change. Nonthermal plasmas are advantageous for this purpose because they operate at ambient conditions and can be easily scaled-up. In this study, we attempt the CO2 splitting into CO and O-2 in a parallel plate packed-bed plasma reactor moderated with Lead Zirconate Titanate (PZT) as fermelectric component, achieving conversion rates and energy efficiencies higher than those obtained with BaTiO3 in our experimental device. The analysis of the reaction mechanisms with optical emission spectroscopy under various operating conditions has shown a direct correlation between energy efficiency and intensity of CO* emission bands. These results and those obtained with a LiNbO3 plate placed onto the active electrode suggest that high temperature electrons contribute to the splitting of CO2 through an enhancement in the formation of CO2+ intermediate species. Results obtained for CO2 + O-2 mixtures confirm this view and suggest that back recombination processes involving CO and O-2 may reduce the overall splitting efficiency. The study of mixtures of CO2 and dry air has proved the capacity of fermelectric packed-bed reactors to efficiently decompose CO2 with no formation of harmful NxOy subproducts in conditions close to those in real facilities. The found enhancement in energy efficiency with respect to that found for the pure gas decomposition supports that new reaction pathways involving nitrogen molecules are contributing to the dissociation reaction. We conclude that PZT moderated packed-bed plasma reactors is an optimum alternative for the decompositon of CO2 in real gas flows and ambient conditions.
Febrero, 2022 | DOI: 10.1016/j.cej.2021.133066
Reactividad de Sólidos
Effect of the Processing Parameters on the Porosity and Mechanical Behavior of Titanium Samples with Bimodal Microstructure Produced via Hot Pressing
Chavez-Vasconez, R; Lascano, S; Sauceda, S; Reyes-Valenzuela, M; Salvo, C; Mangalaraja, RV; Gotor, FJ; Arevalo, C; Torres, YMaterials, 15 (2022) 136
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Commercially pure (c.p.) titanium grade IV with a bimodal microstructure is a promising material for biomedical implants. The influence of the processing parameters on the physical, microstructural, and mechanical properties was investigated. The bimodal microstructure was achieved from the blends of powder particles with different sizes, while the porous structure was obtained using the space-holder technique (50 vol.% of ammonium bicarbonate). Mechanically milled powders (10 and 20 h) were mixed in 50 wt.% or 75 wt.% with c.p. titanium. Four different mixtures of powders were precompacted via uniaxial cold pressing at 400 MPa. Then, the specimens were sintered at 750 degrees C via hot pressing in an argon gas atmosphere. The presence of a bimodal microstructure, comprised of small-grain regions separated by coarse-grain ones, was confirmed by optical and scanning electron microscopies. The samples with a bimodal microstructure exhibited an increase in the porosity compared with the commercially available pure Ti. In addition, the hardness was increased while the Young's modulus was decreased in the specimens with 75 wt.% of the milled powders (20 h).
Enero, 2022 | DOI: 10.3390/ma15010136
Química de Superficies y Catálisis
Boosting water activation determining-step in WGS reaction on structured catalyst by Mo-doping
Garcia-Moncada, N; Jurado, L; Martinez-Tejada, LM; Romero-Sarria, F; Odriozola, JACatalysis Today, 383 (2022) 193-204
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Proton conductors Mo-Eu-Zr mixed oxide systems were synthesized and further mixed with a conventional Pt/CeO2/Al2O3 catalyst to develop a highly efficient water-gas-shift (WGS) catalyst. The designed catalyst, once structured, allows reach the equilibrium conversion at medium temperatures (similar to 350 degrees C) at 80 L.g(-1) h(-1) space velocity. The ability of the proton conductor to maintain an elevated water concentration at the metal-support interface by Grotthuss' mechanism boosts the catalytic activity in WGS reaction.
The Mo-containing proton conductor is extensively characterized allowing to establish the formation of molybdenum oxide phases nucleating on top of the Eu sites in Eu-Zr oxide solid solution. [MoO4](2-) to [Mo7O24](6-) clusters nucleates at low Mo contents resulting in a alpha-MoO3 layer on increasing its content. In presence of H-2, Mobronzes are formed from similar to 200 degrees C enhancing water concentration at the surfaces and boosting the catalytic activity in the WGS reaction. These results pave the way for developing lower volume WGS reactors.
Enero, 2022 | DOI: 10.1016/j.cattod.2020.06.003
Materiales de Diseño para la Energía y Medioambiente
The Response of Tomato Fruit Cuticle Membranes Against Heat and Light
Benitez, JJ; Moreno, AG; Guzman-Puyol, S; Heredia-Guerrero, JA; Heredia, A; Dominguez, EFrontiers in Plant Science, 12 (2022) 807723
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Two important biophysical properties, the thermal and UV-Vis screening capacity, of isolated tomato fruit cuticle membranes (CM) have been studied by differential scanning calorimetry (DSC) and UV-Vis spectrometry, respectively. A first order melting, corresponding to waxes, and a second order glass transition (T-g) thermal events have been observed. The glass transition was less defined and displaced toward higher temperatures along the fruit ripening. In immature and mature green fruits, the CM was always in the viscous and more fluid state but, in ripe fruits, daily and seasonal temperature fluctuations may cause the transition between the glassy and viscous states altering the mass transfer between the epidermal plant cells and the environment. CM dewaxing reduced the T-g value, as derived from the role of waxes as fillers. T-g reduction was more intense after polysaccharide removal due to their highly interwoven distribution within the cutin matrix that restricts the chain mobility. Such effect was amplified by the presence of phenolic compounds in ripe cuticle membranes. The structural rigidity induced by phenolics in tomato CMs was directly reflected in their mechanical elastic modulus. The heat capacity (Cp-rev) of cuticle membranes was found to depend on the developmental stage of the fruits and was higher in immature and green stages. The average Cp-rev value was above the one of air, which confers heat regulation capacity to CM. Cuticle membranes screened the UV-B light by 99% irrespectively the developmental stage of the fruit. As intra and epicuticular waxes contributed very little to the UV screening, this protection capacity is attributed to the absorption by cinnamic acid derivatives. However, the blocking capacity toward UV-A is mainly due to the CM thickness increment during growth and to the absorption by flavone chalconaringenin accumulated during ripening. The build-up of phenolic compounds was found to be an efficient mechanism to regulate both the thermal and UV screening properties of cuticle membranes.
Enero, 2022 | DOI: 10.3389/fpls.2021.807723
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