Electrocatalysis on shape-controlled metal nanoparticles: Progress in surface cleaning methodologies

The use of shape-controlled metal nanoparticles has produced not only a clear enhancement in the electrocatalytic activity of different reactions of interest but also a better understanding of the effect of the surface structure on nanoscaled materials. However, it is well-accepted that a correct understanding of the correlations between shape/surface structure and electrochemical reactivity indispensably requires the use of clean surfaces. In this regard, and considering that most of the synthetic methodologies available in the literature for the preparation of these shaped metal nanoparticles employ capping agents, the development of effective surface cleaning methodologies able to remove such capping agents from the surface of the corresponding nanoparticles, becomes an extremely important prerequisite to subsequently evaluate their electrocatalytic properties for any reaction of interest. Consequently, in this contribution, we summarize the most relevant advances about surface cleaning procedures applied to different shaped metal nanoparticles for electrocatalytic purposes. It is worth mentioning that this work will only include contributions in which the surface cleanness of the samples is specifically evaluated using well-established electrochemical tools.This work has been financially supported by the MINECO of Spain through project CTQ2013-48280-C3-3-R. JSG acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante

Surface structured platinum electrodes for the electrochemical reduction of carbon dioxide in imidazolium based ionic liquids

The direct CO2 electrochemical reduction on model platinum single crystal electrodes Pt(hkl) is studied in [C2mim+][NTf2−], a suitable room temperature ionic liquid (RTIL) medium due to its moderate viscosity, high CO2 solubility and conductivity. Single crystal electrodes represent the most convenient type of surface structured electrodes for studying the impact of RTIL ion adsorption on relevant electrocatalytic reactions, such as surface sensitive electrochemical CO2 reduction. We propose here based on cyclic voltammetry and in situ electrolysis measurements, for the first time, the formation of a stable adduct [C2mimH–CO2−] by a radical–radical coupling after the simultaneous reduction of CO2 and [C2mim+]. It means between the CO2 radical anion and the radical formed from the reduction of the cation [C2mim+] before forming the corresponding electrogenerated carbene. This is confirmed by the voltammetric study of a model imidazolium-2-carboxylate compound formed following the carbene pathway. The formation of that stable adduct [C2mimH–CO2−] blocks CO2 reduction after a single electron transfer and inhibits CO2 and imidazolium dimerization reactions. However, the electrochemical reduction of CO2 under those conditions provokes the electrochemical cathodic degradation of the imidazolium based RTIL. This important limitation in CO2 recycling by direct electrochemical reduction is overcome by adding a strong acid, [H+][NTf2−], into solution. Then, protons become preferentially adsorbed on the electrode surface by displacing the imidazolium cations and inhibiting their electrochemical reduction. This fact allows the surface sensitive electro-synthesis of HCOOH from CO2 reduction in [C2mim+][NTf2−], with Pt(110) being the most active electrode studied.This work has been partially financed by Generalitat Valenciana through Ayudas para la realización de proyectos de I+D para grupos de investigación emergentes (GV/2014/096) and by the MICINN (project CTQ2013-48280-C3-3-R)

Electrocatalytic studies on imidazolium based ionic liquids: defining experimental conditions

The number of publications devoted to studying electrochemical reactions in room temperature ionic liquids (RTILs) is constantly growing, but very few of them have been devoted to defining proper experimental conditions to obtain reproducible electrochemical results. In this work, we demonstrate that the combination of a proper RTIL purification treatment and a filtered Ar gas stream allow us to obtain featureless voltammograms in [C4mim][BF4], [C4mim][NTf2], and [C4m2im][NTf2], which otherwise present signals associated with different types of impurities such as water and some minor electroactive impurities acquired during the RTIL synthesis process. Moreover, we demonstrate that bubbling Ar, or another inert gas, through the electrolyte in order to purge O2 dissolved in RTILs is one of the major sources of water and O2 impurities incorporated in RTILs within the electrochemical cell. To overcome this source of water uptake, we have incorporated a gas stream purification filter before the gas reaches the RTIL in the electrochemical cell. To illustrate the effect of these impurities in relevant electrocatalytic studies, we study the electrocatalytic reduction of CO2 on Pt nanoparticles and the key role of an appropiate filter when the CO2 gas stream is bubbled within imidazolium based RTILs. Our cyclic voltammetric studies point out that CO2 electroreduction on Pt nanoparticles only presents activity in [C4mim][NTf2] and [C4m2im][NTf2], thus suggesting that the C-2 position on the imidazolium ring is not the key position in CO2 electrochemical reduction. In contrast, the same Pt nanoparticles are inactive towards CO2 electroreduction in [C4mim][BF4], which is a more hydrophilic RTIL.The authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) (projects CTQ2013-48280-C3-3-R and CTQ2016-76231-C2-2-R) (AEI/FEDER, UE) and from the CNRS (projet Défi Instrumentation aux limites 2015). J. S.-G. acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante (UATALENTO16-02). C. M. S.-S. acknowledges financial support from the University of Alicante, visiting researcher grant INV16-15

Sessile Biofouling on Electrolytic Carbonated Structures: Stages of Colonization and Succession

The ecological succession has been widely studied by means of biofouling assemblages among different substrates, and mainly targeted in early stages on artificial ones. The present study focuses on biofouling that colonizes carbonated structures, a material similar to the natural substrate produced by the electrolysis of seawater, which is relatively very little studied. We have observed the colonization of sessile macrofouling of the port of Alicante (SE Spain, Western Mediterranean) on two types of substrates (electrolytic carbonated and steel) over 12 months of succession. The assemblages of both substrates have been analyzed by means of diversity indexes and multivariate analysis (PERMANOVA and SIMPER) in order to see the differences over time. The carbonated substrate has presented a community with higher values of biological diversity, structure and complexity, although the differences in species composition between substrates are not evident during all immersion periods. Thus, these results seem to indicate that, even after 12 months of immersion, communities are still in a dynamic successional stage.This research forms part of the ThinkInAzul program and was funded by Ministerio de Ciencia e Innovación with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (THINKINAZUL/2021/014)

Early colonization of sessile megabenthos on electrolytic carbonated structures (Alicante's harbor, Western Mediterranean)

Biofouling in different artificial substrata was done to determine the differences in biofouling assemblages among different substrates. However, studies on biofouling on natural substrates like electrolytic carbonated ones are lacking. These substrates have a great potential for coral reef restoration in tropical areas and for biofilter construction. Thus, this study was done to examine the colonization of sessile macrofouling in the port of Alicante (SE Spain, Western Mediterranean) on two types of substrata: electrolytic carbonated and bare steel (as control) over three months of immersion (October 2019–January 2020). The community diversity was studied through different biotic parameters and abundance of assemblages, and preference of organisms according to their status and functional group (active filter feeders). Univariate and multivariate analyses (PERMANOVA and SIMPER) were also done to examine the differences between carbonate and control substrata. The carbonated substrate had a more structured community and higher abundance, recruitment, and diversity indexes than the bare steel. Moreover, filter feeders (Porifera, Bivalvia, and Ascidiacea) were more abundant, and most of them only appeared in the carbonated substrate. These results show the potential of carbonated structures as biofilters.This study forms part of the ThinkInAzul program and was supported by Ministerio de Ciencia e Innovación with funding from European Union NextGenerationEU (PRTRC17.I1) and by Generalitat Valenciana (THINKINAZUL/2021/014)

Dual-plate gold-gold microtrench electrodes for generator-collector voltammetry without supporting electrolyte

A gold-gold dual-plate microtrench electrode system based on two oppositely placed gold surfaces with 5 mm length, 17 μm average depth, and 6 μm inter-electrode gap is employed in generator-collector configuration in a four-electrode cell (counter electrode, reference electrode, and two independent working electrodes denoted “generator” – with scanning potential – and “collector” – with fixed potential). The dual-plate microtrench electrodes were investigated for (i) the reduction of Ru(NH3)6 3+, (ii) the oxidation of ferrocenemethanol, and (iii) the oxidation of iodide in aqueous media, all as a function of supporting electrolyte concentration. It is shown that due to the inter-electrode feedback character of the generator-collector currents, well-defined steady state sensor responses are obtained for the collector electrode even in the absence of added electrolyte. The variation in the mass transport limited steady state current (measured at the collector electrode) with addition/removal of supporting electrolyte remains low (compared to unexpectedly stronger effects caused by the switch between reduction and oxidation conditions at the collector electrode). Microtrench electrode systems are suggested for sensing applications without/with varying levels of supporting electrolyte.</p

Influence of Bitartrate Ion Concentration in the Copper Electrodeposition Onto a Polycrystalline Gold Electrode

In the present work, the influence of the concentration of bitartrate ions (HT) on the copper electrodeposition process was analyzed. The study was carried out from an aqueous solution containing 0.001 M of CuX (where X = (NO3–)2 ,(Cl–)2, SO42–) and x M KHT (where x = 0.005 M, 0.01 M, and 0.015 M). From voltammetric and chronoamperometric studies, the results indicate that copper electrodeposition is a diffusion-controlled process. The current density transients were well described through a kinetic mechanism involving capacitive and faradaic contributions. The diffusion coefficient values of Cu1+ and Cu2+ result to be similar at the different concentration values of potassium bitartrate used in this work. This work is licensed under a Creative Commons Attribution 4.0 International License

Platinum Recovery Techniques for a Circular Economy

Platinum and other metals are very scarce materials widely used in the energy and transportation sector among other sectors. Obtaining Platinum is becoming more difficult due to its scarcity on earth and because of the high amount of energy and water used for its extraction. In this regard, the recycling of platinum is necessary for sustainable technologies and for reaching a circular economy towards this expensive and rare metal. Conventional methods for platinum recycling make use of enormous amounts of energy for its recovery, which makes them not very attractive for industry implementation. Furthermore, these processes generate very toxic liquid streams and gas wastes that must be further treated, which do not meet the green environmental point of view of platinum recycling. Consequently, new advanced technologies are arising aiming to reach very high platinum recovery rates while being environmentally friendly and making a huge reduction of energy use compared with the conventional methods. In this review, conventional platinum recovery methods are summarized showing their limitations. Furthermore, new and promising approaches for platinum recovery are reviewed to shed light on about new and greener ways for a platinum circular economyEl platino y otros metales son materiales muy escasos ampliamente utilizados en el sector de la energía y el transporte, entre otros sectores. La obtención de platino es cada vez más difícil debido a su escasez en la tierra y por la gran cantidad de energía y agua que se utiliza para su extracción. En este sentido, el reciclaje de platino es necesario para tecnologías sostenibles y para alcanzar una economía circular hacia este metal caro y raro. Los métodos convencionales para el reciclaje del platino utilizan enormes cantidades de energía para su recuperación, lo que los hace poco atractivos para su implementación en la industria. Además, estos procesos generan corrientes líquidas muy tóxicas y desechos gaseosos que deben tratarse más, que no cumplen con el punto de vista ambiental verde del reciclaje de platino. Como consecuencia, Están surgiendo nuevas tecnologías avanzadas con el objetivo de alcanzar tasas de recuperación de platino muy altas, al mismo tiempo que son respetuosas con el medio ambiente y reducen enormemente el uso de energía en comparación con los métodos convencionales. En esta revisión, se resumen los métodos convencionales de recuperación de platino mostrando sus limitaciones. Además, se revisan enfoques nuevos y prometedores para la recuperación de platino para arrojar luz sobre formas nuevas y más ecológicas para una economía circular de platin

Realización de un congreso online para fomentar la participación y aprendizaje en reuniones científicas

Los congresos científicos son una herramienta tan valiosa como infrautilizada en el aprendizaje para estudiantes de tercer ciclo y es que, desgraciadamente, éstos no son aprovechados al máximo puesto que las intervenciones en las que los estudiantes plantean dudas o preguntas son prácticamente nulas. Con el objetivo de fomentar la participación de los estudiantes en los congresos científicos, se ha organizado y realizado un congreso online para estudiantes de máster y doctorado en el programa interuniversitario "Electroquímica. Ciencia y Tecnología", empleando la herramienta Moodle. En este congreso, los alumnos han presentado comunicaciones científicas en formato póster y se han llevado a cabo discusiones científicas sobre estas contribuciones. Para fomentar la participación de los alumnos, se han otorgado certificados de participación y premios al estudiante más participativo y al mejor póster. El congreso ha sido evaluado por parte de los participantes mediante una encuesta, con el fin de obtener un feedback para una posible próxima edición del congreso

Celebración del I Congreso Online de Jóvenes Investigadores, herramienta científica de presente y futuro

Históricamente, los congresos científicos son, y han sido, uno de los mecanismos más efectivos para la difusión y el debate del conocimiento. A pesar de ello, un ambiente altamente formal no es el más idóneo para que los estudiantes de tercer ciclo saquen el máximo rendimiento, relegándolos a un segundo plano y anulando prácticamente su participación. Con el reto de propiciar la intervención de los estudiantes de máster y doctorado, fundamentalmente a través de planteamiento de preguntas, se ha organizado y celebrado el I Congreso Online de Jóvenes Investigadores en Electroquímica. Enmarcado en los programas interuniversitarios de máster y doctorado de “Electroquímica. Ciencia y Tecnología”, y mediante la herramienta Moodle, los estudiantes han participado en el congreso mediante comunicaciones en formato de póster. Además, han podido mantener discusiones científicas y expresar sus dudas e inquietudes hacia el trabajo de sus compañeros. Para implicar al alumno, se han otorgado certificados de participación y varios premios, uno de ellos otorgado por los propios estudiantes mediante un sistema de votación. En previsión de próximas ediciones del congreso se hizo una encuesta de satisfacción y sugerencias entre los participantes