Thermodynamic studies of anion adsorption at the Pt(111) electrode surface from glycolic acid solutions

Kinetic glycolic acid (GA) oxidation and thermodynamic glycolate adsorption have been studied on Pt single crystal electrodes. The voltammetric profiles of Pt(111), Pt(100), and Pt(110) in 0.1 M GA are shown, and the effect of the inclusion of steps on the Pt(111) surface has been studied by cyclic voltammetry. For Pt(111) electrode, different concentrations and sweep rates have been applied, revealing that both adsorption and oxidation processes take place. By establishing the appropriate conditions, a complete thermodynamic analysis has been performed by using the electrode potential and the charge as independent variables. Total charge density curves, surface pressure at total charge density and at constant electrode potential were determined to calculate the Gibbs excess and the charge number at constant electrode potential for glycolate adsorption on Pt(111). Maximum glycolate coverage on the surface reaches a value of ∼6.0 × 1014 ions/cm2. Spectroscopic results show the formation of CO2 during the oxidation of glycolic acid, indicating that the cleavage of the C–C bond occurs during the oxidation process.The work was carried out under the financial support by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013)

Concepciones de niños y niñas sobre la inteligencia ¿Qué papel se otorga a las funciones ejecutivas y a la autorregulación?

Intelligence is a construct of notable impact in our sociocultural context, related to a wide range of conceptual and operational definitions which originate positions that highlights cognitive and abstract elements and emotional and social skills, as well was perspectives that are focused on processes underlying the intelligent performance, such as in the case of executive functions (EFs), which are configured as cognitive processes that make it possible the self-regulation (Miyake & Friedman, 2012). Similarly, there are approaches that give intelligence a relevant and predictive role of school performance, an aspect strengthened by the psychometric perspective, where the concept of intelligence has been closely linked to learning. In this line, we also find the classical perspective of crystallized Intelligence of Cattell (1943), which refers to the knowledge acquired through educational and cultural processes. The aim of this study is to know the conceptualizations of intelligence of children aged 8-12, the features they give to them, and the assessment of their own intellectual capacities. The data analysis was carried out through the grounded theory and the results mainly show that participants attribute components referred to the management of school contents and quantitative performance to intelligence. Moreover, the answers show elements related to EFs and self-regulation not only when considering the meaning of the construct, but also while characterizing and evaluating the intelligence performance.La inteligencia constituye un constructo de notable impacto en nuestro contexto sociocultural, evidenciado en un amplio desarrollo de definiciones conceptuales y operacionales, donde surgen aseveraciones que van desde privilegiar elementos de tipo cognitivo y abstracto, a elementos emocionales y sociales, hasta perspectivas que se enfocan en los procesos que subyacen al desempeño inteligente, como es el caso de las funciones ejecutivas (FE), las cuáles se configuran como procesos cognitivos que posibilitan la autorregulación (Miyake & Friedman, 2012). De igual modo, existen enfoques que otorgan a la inteligencia un rol relevante y predictivo del rendimiento escolar, aspecto fortalecido por la perspectiva psicométrica donde el concepto de inteligencia se ha vinculado estrechamente con el aprendizaje. En esta línea, también encontramos la perspectiva clásica de inteligencia cristalizada de Cattell (1943), la cual hace alusión al conocimiento adquirido a través de procesos educativos y culturales. El objetivo de este estudio fue conocer las concepciones que niñas y niños, de edades comprendidas entre 8 y 12 años, otorgan al concepto de inteligencia, las características que le atribuyen y la valoración que hacen de las propias capacidades intelectuales. El análisis de los datos se llevó a cabo mediante la teoría fundamentada y los resultados evidencian principalmente que los participantes atribuyen al constructo de inteligencia componentes referidos al manejo de contenidos escolares y al rendimiento cuantitativo; además de poner en manifiesto elementos relacionados con las FE y la autorregulación no sólo en la significación que hacen del constructo, sino también al caracterizar y valorar el desempeño inteligente

Concepciones de niños y niñas sobre la inteligencia ¿Qué papel se otorga a las funciones ejecutivas y a la autorregulación?

Intelligence is a construct of notable impact in our sociocultural context, related to a wide range of conceptual and operational definitions which originate positions that highlights cognitive and abstract elements and emotional and social skills, as well was perspectives that are focused on processes underlying the intelligent performance, such as in the case of executive functions (EFs), which are configured as cognitive processes that make it possible the self-regulation (Miyake & Friedman, 2012). Similarly, there are approaches that give intelligence a relevant and predictive role of school performance, an aspect strengthened by the psychometric perspective, where the concept of intelligence has been closely linked to learning. In this line, we also find the classical perspective of crystallized Intelligence of Cattell (1943), which refers to the knowledge acquired through educational and cultural processes. The aim of this study is to know the conceptualizations of intelligence of children aged 8-12, the features they give to them, and the assessment of their own intellectual capacities. The data analysis was carried out through the grounded theory and the results mainly show that participants attribute components referred to the management of school contents and quantitative performance to intelligence. Moreover, the answers show elements related to EFs and self-regulation not only when considering the meaning of the construct, but also while characterizing and evaluating the intelligence performance.La inteligencia constituye un constructo de notable impacto en nuestro contexto sociocultural, evidenciado en un amplio desarrollo de definiciones conceptuales y operacionales, donde surgen aseveraciones que van desde privilegiar elementos de tipo cognitivo y abstracto, a elementos emocionales y sociales, hasta perspectivas que se enfocan en los procesos que subyacen al desempeño inteligente, como es el caso de las funciones ejecutivas (FE), las cuáles se configuran como procesos cognitivos que posibilitan la autorregulación (Miyake & Friedman, 2012). De igual modo, existen enfoques que otorgan a la inteligencia un rol relevante y predictivo del rendimiento escolar, aspecto fortalecido por la perspectiva psicométrica donde el concepto de inteligencia se ha vinculado estrechamente con el aprendizaje. En esta línea, también encontramos la perspectiva clásica de inteligencia cristalizada de Cattell (1943), la cual hace alusión al conocimiento adquirido a través de procesos educativos y culturales. El objetivo de este estudio fue conocer las concepciones que niñas y niños, de edades comprendidas entre 8 y 12 años, otorgan al concepto de inteligencia, las características que le atribuyen y la valoración que hacen de las propias capacidades intelectuales. El análisis de los datos se llevó a cabo mediante la teoría fundamentada y los resultados evidencian principalmente que los participantes atribuyen al constructo de inteligencia componentes referidos al manejo de contenidos escolares y al rendimiento cuantitativo; además de poner en manifiesto elementos relacionados con las FE y la autorregulación no sólo en la significación que hacen del constructo, sino también al caracterizar y valorar el desempeño inteligente

The breaking of the C-C bond in ethylene glycol oxidation at the Pt(111) electrode and its vicinal surfaces

Ethylene glycol (EG) oxidation has been studied on Pt(111) and its vicinal surfaces in acidic media by cyclic voltammetry and infrared spectroscopy. Even at Pt(111) the C-C bond is readily broken and CO is formed at low potentials. Both types of steps catalyze the EG oxidation to CO2, being the {110} steps the most catalytic for the splitting of the C-C bond. Spectroscopic results show that glycolic acid and oxalic acid are produced mainly at the close-packed terraces.Financial support by MICINN (project No. CTQ2010-16271)

On the oxidation mechanism of C1-C2 organic molecules on platinum. A comparative analysis

The rational design of better electrocatalysts for the oxidation of C1–C2 organic molecules requires the detailed knowledge of their oxidation mechanism. Pt single crystals are powerful tools to study, in a simple way, the surface structure effect on the different reaction pathways. Here, the oxidation mechanism of these molecules is compared so that the knowledge gained with the simpler mechanism is transferred in the analysis of the more complex ones. The goal is to design strategies so that the platinum electrodes improve their performance in their oxidation by the appropriate modification with other elements by attacking the bottlenecks in the reaction mechanism.Financial support from Ministerio de Ciencia e Innovación (Project no. PID2019-105653GB-100 and FJC2018-038607-I) and Generalitat Valenciana (Projects PROMETEO/2020/063 and CDEIGENT/2019/018) is acknowledged

Weakening the C – C bond: On the behavior of glyoxylic acid on Pt(111) and its vicinal surfaces

Adsorption and oxidation of glyoxylic acid (GA) on platinum single crystals were investigated by spectroelectrochemical techniques. Among basal planes, Pt(111) is taken as a model surface for reactivity studies in order to point out the Csingle bondC bond breaking. For a standard GA concentration (0.1 M), self-poisoning by adsorbed CO (COads) is the main process dominating the positive-going sweep. The presence of (110) steps on (111) terraces contribute in the Csingle bondC bond cleavage, leading to CO formation, while (100) steps do not show a significant effect. Poison stripping allows GA oxidation in a lower potential range in the negative-going sweep. By working with different GA concentrations (10− 5–0.1 M), surface blockage is hindered, pointing out an alternative reaction pathway, where GA is oxidized in a poison-free surface. Fourier transform infrared spectroscopy (FTIR) experiments allowed the identification of CO2, formic (FA) and oxalic acid (OA) as main products of GA oxidation. We highlight an activity peak at 0.01 M GA, concomitant to the presence of CO2 absorption bands at lower potentials (0.2 V). The formation of CO2 at potentials where CO cannot be oxidized suggests a change in the preferential reaction pathway, where GA is completely oxidized through an active intermediate distinct to COads.This work was carried out under financial support of MICINN (project no. CTQ2013-44083-P). R.M.H. acknowledges support from Generalitat Valenciana under Santiago Grisolia Program (GRISOLIA/2013/008)

On the oxidation of isopropanol on platinum single crystal electrodes. A detailed voltammetric and FTIR study

Isopropanol oxidation is studied on platinum single crystals using electrochemical techniques and FTIR spectroscopy at different isopropanol concentrations. Isopropanol oxidation is found to be facilitated by the presence of adsorbed OH on the electrode surface, which reacts with an isopropanol molecule to yield the adsorbed alkoxide. Thus, when sulfuric acid is used as the supporting electrolyte instead of perchloric acid, oxidation currents diminish drastically since sulfate hinders OH adsorption. Kinetic measurements reveal that the chemical reaction between adsorbed OH and isopropanol is the rate-determining step in the mechanism. Voltammetric and FTIR experiments show that acetone is the major product of the reaction. On the Pt(111) surface, acetone is produced exclusively, and oxidation currents are controlled by diffusion since, on this electrode, acetone is not adsorbed and the adsorbed OH mobility is high. The adsorption of acetone-related species on the Pt(110) surface, which partially block the surface, leads to slightly lower currents. On the other hand, the Pt(100) electrode is the one showing significant rates for the C–C bond cleavage, yielding adsorbed CO and other species. Although this route is a minor path, the surface blockage by these species leads to a significant diminution of the currents.This research was funded by Ministerio de Ciencia e Innovación (Spain) grant number PID2019-105653 GB-I00) and Generalitat Valenciana (Spain) grant number PROMETEO/2020/063. RMAA acknowledges the financial support from Generalitat Valenciana (CDEIGENT/2019/018). DSM thanks the Government of Argelia for the award of a doctoral fellowship to support her studies at the University of Alicante

Understanding the electrochemical hydrogenation of acetone on Pt single crystal electrodes

The heterogeneous upgrading of biomass by means of electrocatalytic hydrogenation is an attractive way to refine products for industrial and pharmaceutical purposes. Also, the efficient electrochemical reduction of carbonyl compounds can act as hydrogen vectors, and therefore energy vectors. In this manuscript, we render further fundamental insights into the electrochemical reduction of acetone as a model molecule of carbonyl compounds. The structural sensitivity of the reaction is demonstrated by using platinum single crystal electrodes with low Miller indices and stepped electrodes with (110) terraces and either (111) or (100) monoatomic steps. Among the basal planes, Pt(110) is the only one active for the electroreduction of acetone. The inclusion of (111) steps on the (110) terraces does not significantly alter the behavior of Pt(110), but increasing the (100) step density has been observed to decrease the activity. We attribute this different performance to a geometrical effect of the active sites. By using different supporting electrolytes, we have found that sulfate competes with acetone for the surface sites, thus modifying the adlayer interfacial structure and hampering acetone reactivity.This research was funded by Ministerio de Ciencia e Innovación (Spain) grant number PID2019-105653GB-I00), Generalitat Valenciana (Spain) grant number PROMETEO/2020/063. RMAA. acknowledges the financial support from Generalitat Valenciana (CDEIGENT/2019/018)

Evidence of Local pH Changes during Ethanol Oxidation at Pt Electrodes in Alkaline Media

Local changes of the interfacial pH can significantly affect the rate and mechanism during the course of an electrodic reaction. For instance, different pH values will have a significant effect on the equilibrium properties of both solution and surface species, altering the reactions kinetics. Ethanol oxidation at platinum electrodes in alkaline media involves the fast consumption of OH− species that will change the local pH at the electrode surface, decreasing the reaction rate. In this study, the local pH change during ethanol oxidation in alkaline media is accomplished by using rotating ring-disc electrode (RRDE) experiments. The current at the ring when polarized at the onset of hydrogen evolution serves as a measure of the local pH in the vicinity of the electrode. The results show that the current at the ring at 0.1 V (vs. RHE) becomes more negative during ethanol oxidation, owing to a change in the equilibrium potential of the hydrogen evolution reaction caused by a change in the local pH.Financial support from Aalto University, Academy of Finland, MINECO, and Generalitat Valenciana through projects CTQ2013–44083-P and PROMETEOII/2014/013 is acknowledged