Tuning the Integration Rate of Ce(Ln)O2 Nanoclusters into Nanoparticulated ZrO2 Supports: When the Cation Size Matters

Three nanostructured catalysts with low total rare earth elements (REEs) content (i.e., 15 mol.%) were prepared by depositing CeO(2)or Ln(3+)-doped CeO2(Ln(3+)= Y(3+)or La3+; Ln/Ce = 0.15) on the surface of ZrO(2)nanoparticles, as nanometre-thick, fluorite-type clusters. These samples were subjected to successive reduction treatments at increasing temperatures, from 500 to 900 degrees C. A characterisation study by XPS was performed to clarify the diffusion process of cerium into the bulk of ZrO(2)crystallites upon reduction to yield Ce(x)Zr(1-x)O(2-delta)surface phases, and the influence of the incorporation of non-reducible trivalent REE cations, with sizes smaller (Y3+) and larger (La3+) than Ce(4+)and Ce3+. For all nanocatalysts, a reduction treatment at a minimum temperature of 900 degrees C was required to accomplish a significant cerium diffusion. Notwithstanding, the size of the dopant noticeably affected the extent of this diffusion process. As compared to the undoped ZrO2-CeO(2)sample, Y(3+)incorporation slightly hindered the cerium diffusion, while the opposite effect was found for the La3+-doped nanocatalyst. Furthermore, such differences in cerium diffusion led to changes in the surface and nanostructural features of the oxides, which were tentatively correlated with the redox response of the thermally aged samples

Tailoring CO2 adsorption and activation properties of ceria nanocubes by coating with nanometre-thick yttria layers

[EN] Ceria (CeO2) is a ubiquitous component in catalysts for environmental protection processes, especially those devoted to CO2 valorisation. Aimed at preparing ceria-based nanomaterials with enhanced CO2 adsorption and activation properties, both the surface acid-base and redox features of ceria nanocubes were modulated by a novel, simple, wet chemistry synthetic strategy consisting of their coating with yttria (Y2O3) layers of variable thickness in the nanometre scale. The as-synthesised samples were characterised with special attention to their surface basicity and reducibility. Characterisation results revealed that the surface doping with yttria not only improved both the reducibility at low temperature and CO2 adsorption capacity of ceria nanocubes, but also introduced a variety of basic sites with different strength. Finally, the careful control of the yttria layer thickness allowed to modulate these effects and thereby the ability of nanostructured ceria to adsorb and activate the CO2 molecule

Methanation of carbon dioxide over ceria-praseodymia promoted Ni-alumina catalysts. Influence of metal loading, promoter composition and alumina modifier

[EN] Two series of ceria-praseodymia promoted Ni-alumina catalysts were prepared from two different commercial modified alumina supports (3.5 wt% SiO2-Al2O3 and 4.0 wt% La2O3-Al2O3) by the incipient wetness impregnation method in two successive steps. The resulting materials were characterized in terms of their physicochemical properties by means of N2 physical adsorption at −196 °C, powder X-ray diffraction (XRD) and temperature programmed reduction with H2 (H2-TPR). Furthermore, the as-prepared catalysts were tested for the CO2 methanation reaction in a fixed-bed reactor at atmospheric pressure, gas hourly space velocity (GHSV) of 72,000 cm3·(h·gcat)−1 and CO2/H2 molar ratio of 1/4 over the temperature range from 25 up to 850 °C. The influence of the nominal Ni loading (3, 5 and 10 wt%), molar composition of the Ce/Pr mixed oxide promoter (80/20 and 60/40), and alumina modifier (silica and lanthana) on the catalytic performance was carefully analyzed. Among these three composition parameters, the alumina dopant and especially the Ni content appear to have by far a much more pronounced effect on both the CO2 conversion and CH4 selectivity as compared to the Ce/Pr mixed oxide composition. Specifically, from the catalytic tests the sample containing a 10 wt% Ni loading, a Ce/Pr mixed oxide promoter of 80/20 molar composition, and silica as modifier provides the highest catalytic activity in terms of CO2 conversion and CH4 selectivity. Such behaviour has been ascribed to a complex interplay between several factors, mainly the larger fraction of catalytically active β-type NiO specie

The educational e-portfolio: preliminary evidence of its relationship with student\u2019s self-efficacy and engagement

The educational use of portfolios has been increasing in the last few years, especially as technology has also developed electronic versions of portfolios. Although there is abundant information about their benefits and practice description, few studies provide empirical evidence of their implementation. The objective of this study was to provide initial evidence about the use of the portfolio in higher education. Concretely, we aimed 1) to explore the correlation between students’ performance on the portfolio and their performance on more traditional assessment methods 2) to explore whether student’s personal variables predict performance in key elements of the e-portfolio, such as individual reflections, and if these contribute to general academic performance in the course, and 3) to evaluate whether the use of the e-portfolio during a semester changes the students’ self-efficacy and engagement. For this purpose, an initial sample of 73 students were recruited, and an e-portfolio (based on Mahara) was implemented over a semester. The results showed that performance on the portfolio correlated with the score obtained on multiple choice tests. There was an increase in self-efficacy after one semester of e-portfolio implementation, and engagement proved to be an important predictor of the final course grade through the mediation of individual reflections. These results offer preliminary and promising evidence about the relationship of a specific element of e-portfolios, individual reflections with several variables related to academic achievement such as self-efficacy and engagement

Thermocatalytic CO2 Conversion over a Nickel-Loaded Ceria Nanostructured Catalyst: A NAP-XPS Study

Despite the increasing economic incentives and environmental advantages associated to their substitution, carbon-rich fossil fuels are expected to remain as the dominant worldwide source of energy through at least the next two decades and perhaps later. Therefore, both the control and reduction of CO2 emissions have become environmental issues of major concern and big challenges for the international scientific community. Among the proposed strategies to achieve these goals, conversion of CO2 by its reduction into high added value products, such as methane or syngas, has been widely agreed to be the most attractive from the environmental and economic points of view. In the present work, thermocatalytic reduction of CO2 with H-2 was studied over a nanostructured ceria-supported nickel catalyst. Ceria nanocubes were employed as support, while the nickel phase was supported by means a surfactant-free controlled chemical precipitation method. The resulting nanocatalyst was characterized in terms of its physicochemical properties, with special attention paid to both surface basicity and reducibility. The nanocatalyst was studied during CO2 reduction by means of Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS). Two different catalytic behaviors were observed depending on the reaction temperature. At low temperature, with both Ce and Ni in an oxidized state, CH4 formation was observed, whereas at high temperature above 500 degrees C, the reverse water gas shift reaction became dominant, with CO and H2O being the main products. NAP-XPS was revealed as a powerful tool to study the behavior of this nanostructured catalyst under reaction conditions

The use of voice notes as an efficient answer to students' doubts about their learning process

[EN] University teachers receive a large volume of e-mails from students, which implies a significant workload. The objective of this study was to determine if answering students' emails with voice notes would reduce the time spent by teachers on this task. In addition, the effect of the use of voice notes on students was assessed, specifically on academic engagement (UWES-S-17 scale) and on their expectations of the benefit derived from the use of this strategy. For this purpose, 60 students were evaluated before (Pre-test) and after (Post-test) the introduction of the voice notes by the teacher. Results showed that the students had very positive expectations, since they considered that this strategy would benefit their learning. In fact, students increased their satisfaction with the e-mail system. However, no significant improvements were observed on academic engagement or in the time spent by the teacher responding to e-mails. In conclusion, voice notes appear to be an appealing resource to answer students' e-mails, however, in order to the full potential of this tool, a long-term follow-up study would be necessary.[ES] El profesorado universitario recibe un gran volumen de emails provenientes del alumnado, lo que implica una importante carga de trabajo. El presente estudio planteó como objetivo determinar si la contestación a las dudas de aprendizaje del alumnado con notas de audio permitía disminuir el tiempo dedicado por el profesorado a esta tarea. Además, se evaluó su efecto sobre el alumnado, específicamente sobre su compromiso académico (escala UWES-S-17) y sobre sus expectativas del beneficio derivado de esta estrategia. Para ello 60 estudiantes fueron evaluados antes (Pre-test) y después (Post-test) de la introducción de las notas de audio por parte del docente. Los resultados muestran que los estudiantes tienen expectativas muy positivas, ya que consideran que esta estrategia puede beneficiar su aprendizaje. De hecho, se registró un aumento de la satisfacción con el sistema de correo electrónico. Sin embargo, no se redujo el número de horas dedicadas por el profesorado a contestar emails ni se registró un aumento en el compromiso académico. En conclusión, las notas de audio parecen un recurso muy prometedor para contestar a las dudas del alumnado por email, sin embargo, para poder evaluar todos los beneficios derivados sería necesario realizar un estudio de seguimiento a largo plazo.Nos gustaría agradecer a la Universidad de Zaragoza (Vicerrectorado de Política Académica) por la financiación del presente estudio (PIIDUZ_21_130).Ferrer-Pérez, C.; Blanco-Gandía, M.; Montagud-Romero, S.; Sánchez-Pérez, N.; López-Crespo, G. (2022). Empleo de las notas de audio como respuesta eficiente a las dudas del alumnado sobre su proceso de aprendizaje. Editorial Universitat Politècnica de València. 1256-1263. https://doi.org/10.4995/INRED2022.2022.157971256126

Enhanced Artificial Enzyme Activities on the Reconstructed Sawtoothlike Nanofacets of Pure and Pr-Doped Ceria Nanocubes

In this work, a simple one-step thermal oxidation process was established to achieve a significant surface increase in {110} and {111} nanofacets on well-defined, pure and Pr-doped, ceria nanocubes. More importantly, without changing most of the bulk properties, this treatment leads to a remarkable boost of their enzymatic activities: from the oxidant (oxidase-like) to antioxidant (hydroxyl radical scavenging) as well as the paraoxon degradation (phosphatase-like) activities. Such performance improvement might be due to the thermally generated sawtoothlike {111} nanofacets and defects, which facilitate the oxygen mobility and the formation of oxygen vacancies on the surface. Finally, possible mechanisms of nanoceria as artificial enzymes have been proposed in this manuscript. Considering the potential application of ceria as artificial enzymes, this thermal treatment may enable the future design of highly efficient nanozymes without changing the bulk composition.This work has been supported by the Ministry of Science, Innovation and Universities of Spain with Reference Numbers of ENE2017-82451-C3-2-R, MAT2016-81118-P and MAT2017-87579-R. The research projects funded by the Natural Science Foundation of Shandong Province (Grant ZR2017LB028), Key R&D Program of Shandong Province (Grant 2018GSF118032), and Fundamental Research Funds for the Central Universities (Grant 18CX02125A) in China are also acknowledged. TEM/STEM data were obtained at DMEUCA node of the Spanish Unique Scientific and Technological Infrastructure (ICTS) of Electron Microscopy of Materials ELECMIM. M. Tinoco thanks the FPU Scholarship Program (Grant AP2010-3737) from Ministry of Education of Spain. H. Pan is grateful for financial support (Grant 201406140130) from the Chinese Scholarship Council to accomplish her Ph.D. study at the University of Cadiz (Spain). J. M. Gonzalez, G. Blanco, and X. Chen are also grateful for the financial support from the joint project (Proyectos Integradores, Grant PI20201) in IMEYMAT of the University of Cadiz

Carbon integral honeycomb monoliths as support of copper catalysts in the Kharasch–Sosnovsky oxidation of cyclohexene

Carbon integral honeycomb monoliths prepared from a natural coal were employed as support of copper catalysts for organic synthetic purposes. In particular good to excellent yields (60–100% as function of the carboxylic acid employed) were obtained in the preparation of allylic esters by the Kharasch–Sosnovsky oxidation of cyclohexene. Different characterization techniques such as chemical analysis by Inductively Coupled Plasma Spectroscopy, nitrogen physisorption, X-ray Diffraction with Rietveld analysis, X-ray Photoelectron and Raman Spectroscopies, Temperature-Programmed Reduction and Scanning Electron Microscopy allowed finding that key parameters such as textural properties, degree of copper precursor decomposition and active phase homogeneity and dispersion can be modulated as function of a simple synthetic variable: the method used to dry the monoliths after impregnation with the metal precursor, either conventional or using microwaves. The results obtained allow understanding the key role of the nature and chemical surrounding (O2 anions or OH groups) of Cu2+ ions in the catalytic activity in the reaction investigated as well as the operating deactivation mechanisms. The use of the structured catalysts here proposed also opens up an interesting alternative to homogeneous catalysis in the field of organic synthesis