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

Industrial synthesis of cysteine derivatives

Comunicación presentada en European Research Conference: "Organic Electrochemistry: Moving Towards Clean and Selective Synthesis", Agelonde-La Londe Les Maures, April 15-19, 1998

Estudio de factibilidad para la elaboración de la harina integral a base de la semilla de Espelta en Latacunga, provincia de Cotopaxi y su comercialización.

La espelta es un cereal antiguo que se cultiva desde hace 7.000 años atrás, se considera la base de todos los trigos existentes en la actualidad. El valor nutritivo de la espelta es superior al trigo, su sabor es dulce y muy gustoso, no contiene grasas saturadas, es de fácil digestión. La espelta es un cereal que se adapta a climas duros, húmedos y fríos, su espiga es aplanada cuyos frutos tienen color tostado claro, los principales países productores de este cereal son en la actualidad: Alemania, Suiza y Francia. Se trata de un cereal bien tolerado por las personas alérgicas al trigo, el cultivo no necesita de químicos para eliminar plantas indeseadas, la dureza de su vaina la protege frente a las plagas. La harina integral de espelta se obtiene mediante un proceso de molienda y tamizado de la semilla. La harina de Espelta, con los ingredientes necesarios sirve para elaborar panes, galletas, fideos, cakes, tortas, coladas, etc., que serán un complemento nutritivo para el organismo. Toda la información para el estudio se la obtuvo a base de investigación por internet, libros, enciclopedias y personas especializadas en la elaboración de harina, etc. El objetivo es obtener una harina integral a base de la semilla de espelta, por medio de un proceso de molienda y tamizado, para dar a conocer los nutrientes, vitaminas y minerales que contiene.Con el desarrollo de la investigación y sus resultados se llegó a la conclusión de que esta semilla no es muy conocida en la población ecuatoriana y por esta razón se desconocen sus nutrientes, vitaminas y minerales, que sirven como un complemento en la nutrición, mejoran la vitalidad y el buen funcionamiento del organismo. El tema de tesis favorecerá a los panificadores y a toda la comunidad en general, es decir, niños, jóvenes, adultos y personas de la tercera edad, ellos contarán con un producto saludable y nutritivo

Editorial of the special issue on advanced electrochemical technologies for environmental applications

This special issue of Separation and Purification Technology gathers 27 articles, which are related to keynotes and oral or poster presentations at the 2nd European Workshop of Electrochemical Engineering entitled ‘New Bridges for a New Knowledge on Electrochemical Engineering’. The workshop was held from 1st to 5th October 2017 in Barcelona (Spain), as a Joint Event of the 10th World Congress of Chemical Engineering (WCCE10). This congress was promoted by the World Chemical Engineering Council (WCEC), the European Federation of Chemical Engineering (EFCE) and the European Society of Biochemical Engineering Sciences (ESBES) to approach researchers and specialists in all areas of chemical engineering and to improve their strategy for the development of innovative processes that will be vital for the society of tomorrow. The joint event was promoted by the Working Party on Electrochemical Engineering (WPEE) of the EFCE and co-organized with the Spanish Excellence Network on Environmental and Energy Applications of the Electrochemical Technology (thus being the 2nd Workshop of E3TECH Network). It took place at Fira de Barcelona, one of the most important trade fair institutions in Europe

Electrochemical synthesis at pre-pilot scale of 1-phenylethanol by cathodic reduction of acetophenone using a solid polymer electrolyte

The pre-pilot scale synthesis of 1-phenylethanol was carried out by the cathodic hydrogenation of acetophenone in a 100 cm2 (geometric area) Polymer Electrolyte Membrane Electrochemical Reactor. The cathode was a Pd/C electrode. Hydrogen oxidation on a gas diffusion electrode was chosen as anodic reaction in order to take advantage of the hydrogen evolved during the reduction. This hydrogen oxidation provides the protons needed for the synthesis. The synthesis performed with only a solid polymer electrolyte, spe, has lower fractional conversion although a higher selectivity than that carried out using a support–electrolyte–solvent together with a spe. However, the difference between these two cases is rather small and since the work-up and purification of the final product are much easier when only a spe is used, this last process was chosen for the pre-pilot electrochemical synthesis of 1-phenylethanol.This work was financially supported by MICINN (Feder) of Spain through the project CTQ2010-20347

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)

Electrochemical reduction of CO2 to formate on nanoparticulated Bi-Sn-Sb electrodes

Human activities during the last century have increased the concentration of greenhouse gases in Earth's atmosphere, mainly carbon dioxide (CO2), and the impacts of climate change around the world are becoming more damaging. Therefore, scientific research is needed to mitigate the consequences of atmospheric CO2, and, among others, the electrochemical CO2 conversion to useful chemicals is one of the most interesting alternatives. Herein, different Bi, Sn and Sb systems were synthesised as nanoparticles, supported on carbon (Vulcan XC-72R) and finally used to manufacture electrodes. The Bi-Sn-Sb nanoparticulated systems and their corresponding electrodes were characterised by TEM, XPS, ICP-OES and SEM. Electrochemical reduction of CO2 to formate was performed in an electrochemical H-type cell in a CO2-saturated KHCO3 and KCl solution. The Bi-Sn-Sb electrodes exhibited good activity and selectivity for the CO2 reduction towards formate. Particularly, Bi95Sb05/C and Bi80Sn10Sb10/C electrodes showed improved stability compared to previous works, keeping values of formate efficiency over 50 % after 24 h.This research was funded by the MICINN Spanish Ministry, through the projects CTQ2016-76231-C2-2-R (AEI/FEDER, UE) and PID2019-108136RB-C32

Electrochemical softening of concentrates from an electrodialysis brackish water desalination plant: Efficiency enhancement using a three-dimensional cathode

The electrochemical softening method to remove hardness from water has not been applied in desalination practice due to a high cathodic area requirement. In this work, the use of a 3D stainless steel wool cathode is proposed to overcome this technical limitation. An extensive comparison between the 3D cathode and a 2D Ti mesh has been presented, showing higher hardness removal for the 3D one. Experiments have been conducted with waters similar to concentrates derived from a brackish water treatment by electrodialysis. In addition, the method has been proved to be efficient for different water compositions in terms of hardness, alkalinity or the presence of an anti-scalant. The main influencing parameters (flow rate and current density) have been studied and it can be concluded that lower flow rates (below 1.2 L h−1) give rise to a better efficiencies and 100 A m−2 is the optimum current density. Moreover, the precipitate was characterised by SEM, EDX and XRD showing that Ca2+ is removed as calcite and aragonite (CaCO3), whereas Mg2+ is precipitated as brucite (Mg(OH)2). Finally, long-term experiments revealed that the 3D stainless steel cathode has a better performance than the 2D Ti mesh, but only at short times

Electrocatalytic hydrogenation of acetophenone using a Polymer Electrolyte Membrane Electrochemical Reactor

The use of a solid polymeric electrolyte, spe, is not commonly found in organic electrosynthesis despite its inherent advantages such as the possible elimination of the electrolyte entailing simpler purification processes, a smaller sized reactor and lower energetic costs. In order to test if it were possible to use a spe in industrial organic electrosynthesis, we studied the synthesis of 1-phenylethanol through the electrochemical hydrogenation of acetophenone using Pd/C 30 wt% with different loadings as cathode and a hydrogen gas diffusion anode. A Polymer Electrolyte Membrane Electrochemical Reactor, PEMER, with a fuel cell structure was chosen to carry out electrochemical reduction with a view to simplifying an industrial scale-up of the electrochemical process. We studied the influence of current density and cathode catalyst loading on this electroorganic synthesis. Selectivity for 1-phenylethanol was around 90% with only ethylbenzene and hydrogen detected as by-products.This work has been financially supported by MICINN (Feder) of Spain through the project CTQ2010-20347

Preparation of Poly(Vinyl) Alcohol/Chitosan Hybrid Membranes Doped with Graphene Nanosheets

The development of ion exchange membrane technology has allowed its introduction in many industrial sectors, such as electrodialysis and electrolysis. Nowadays, membranes are the crucial element in electrochemical energy conversion and storage devices. This work is aimed at examining new eco-friendly membranes materials to improve structural, mechanical, electrical and barrier properties. A simple and ecological synthesis of alkaline anion exchange membranes based on a mixed matrix membrane of chitosan (CS) and poly(vinyl) alcohol (PVA) – CS:PVA polymeric matrix – was developed by using a 50:50 wt. % ratio. The CS:PVA matrix was modified with variable loadings of graphene pristine sheets (GPH) ranging between 0,5 and 4.0 wt. %. The physico-chemical characterization of each of the membranes prepared was carried out in order to examine the topology, structure, thermal stability, surface chemistry, and water content (WC), as well as the ionic conductivity by using electrochemical impedance spectroscopy (EIS). Results revealed that the incorporation of graphene (GPH) into the CS:PVA polymeric matrix leads to the improvement of the thermal stability, and the ionic conductivity of the pristine polymeric matrix. The loading of 1.0 wt. % of GPH into CS:PVA was optimal in terms of specific ionic conductivity that is related to surface chemistry of the membrane, WC, and slight roughness of the membrane topology. The presence of GPH only provided a slight loss of crystallinity of the memebrane compared to the unmodified CS:PVA membrane, which also resulted in the reduction of water content with moderately GPH loadings. With regard to the ionic conductivity, an almost twofold increase was obtained compared to the pure CS:PVA for an optimal loading of 1.0 wt. %.The authors thank the Ministerio de Economía y Competitividad for its financial support (CTQ2013-48280-C3-3-R). Also, Jesús Iniesta gives thanks to Relaciones Internacionales for the PPI grant suppoted by the University of Alicante, Spain