Interface porosity in multilayered all-conducting polymer electrodes

Multilayered films made with at least two different electroactive polymers, in which the least conducting one acts as a dielectric and separates the layers made with the other, behave as efficient electrodes for electrochemical supercapacitors. In this work, we present a simple strategy to develop improved multilayered electrodes with structured interfaces by enhancing the porosity of the dielectric. This has been achieved by growing sodium chloride crystals onto a conducting polymer layer and, after generation of all required layers using the layer-by-layer electrodeposition technique, salt crystals have been eliminated by water etching. Results from morphological and topographical studies on single-layered poly(3,4-ethylenedioxythiophene) (PEDOT), poly(N-methylpyrrole) (PNMPy), and poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (COP), as well as electrochemical investigations on bi-layered films with enhanced porosity at the interface between the two layers, have been used to design new four-layered electrodes. These consist in two layers of PEDOT separated by two layers of nanosegregated COP with a porous interface in the middle. Although the properties of the new four-layered electrodes improve due to the porous interface, the highest specific capacitance corresponds to the two-layered electrode in which two PEDOT layers are separated by an ultra-porous interface.Postprint (author's final draft

Nanophase-segregation in the dielectric layer enhances the charge storage capacity of polymeric electrochemical supercapacitors

Properties related with the charge storage capacity have been evaluated for three-layered films made with two sheets of poly(3,4-ethylenedioxythiophene) separated by a sheet of poly(N-methylpyrrole) or poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (3l-PEDOT/PNMPy or 3l-PEDOT/P(EDOT-co-NMPy), respectively). The most distinctive trend of the copolymer, which shows electrochemical properties intermediate between those of the two homopolymers, is the formation of a biphasic structure, EDOT- and NMPy-rich blocks organizing separately. The ability to exchange charge reversibly is higher for 3l-PEDOT/P(EDOT-co-NMPy) than for 3l-PEDOT/PNMPy, the electroactivity and electrostability of such two 3-layered films being significantly better than that of single-layered PEDOT. Advantages of 3l-PEDOT/P(EDOT-co-NMPy) are mainly based on the nanophase-segregated structure of the copolymer. Thus, the intermediate layer can be considered as random disposition of ultrathin dielectrics having nanometric length and width. In terms of charge storage, the intermediate layer of 3l-PEDOT/P(EDOT-co-NMPy) can be viewed as a thin reservoir filled of heterogeneously distributed nanometric supercapacitors that are connected in series among them and in parallel to the PEDOT layers. The superiority of 3l-PEDOT/P(EDOT-co-NMPy) as organic electrochemical supercapacitor compared to other 3-layered systems, has been proved by powering a red LED bulb.Peer ReviewedPostprint (author's final draft

UV assisted photo reactive polyether-polyesteramide resin for future applications in 3D printing

Among additive manufacturing, photocuring 3D printing technologies are very relevant because of its high printing speed and high precision. However, the limited performance of photosensitive thermoset polymers is the bottleneck for the application of photocuring 3D printing in some fields, particularly in the biomedical sector. Thus, the development of biodegradable and biocompatible materials is highly desirable and of utmost importance. In this work, a biodegradable and non-cytotoxic thermoset polymer for photocuring 3D printing is reported. It consists of an unsaturated polyesteramide bearing phenylalanine, 2-butene-1,4-diol and fumarate building blocks, which is photocured under UV irradiation using a low molecular weight poly(ethylene glycol) diacrylate as crosslinker. The main characteristics of the new thermoset are: (1) very high volumetric and mechanical integrity stabilities, comparable to that of photocured epoxides; (2) very high degradation temperature; (3) very low water absorption capacity; (4) relatively fast enzymatic degradation, reaching 16.5% after 3¿months; and (5) non-cytotoxic response in presence of epithelial cells, even when soluble molecular fragments coming from biodegradation are considered. These properties favor the future utilization of the new polyether-polyesteramide resin in the manufacturing of more sustainable products via 3D printing methods, such as stereolithography, that uses UV sources.Postprint (published version

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Postprint (published version

Degradació d’herbicides s-triazínics mitjançant processos electroquímics d’oxidació avançada

SUMMARY: advanced oxidation processes are nowadays, an effective treatment for waste water polluted with agrochemicals or persistent pollutants, and also are environmentally friendly methods. In the present thesis three herbicides have been studied, atrazine, desmetrine and cyanazine , commonly used to treat crops to remove weeds. These treatments are based on oxidation processes in electrolytic cell with an anode of boron-doped diamond (BDD) and a stainless steel cathode or an oxygen diffusion cathode. BDD anode has been very effective for this purpose since it has a high resistence in many media and has a high oxygen overpotential. Studied conditions for the degradation were carried out taking into account the influence of the pH of the medium, temperature and the presence of catalysts. The methods applied are anodic oxidation, electro- photo and photo electro- Fenton. In the case of Fenton treatment, the necessary hydrogen peroxide to take place the Fenton reaction has been electrogenerated with an air diffusion cathode. In the photo electro -Fenton method, the solution was irradiated with a UV black light lamp. The results demonstrate that the most effective method in all cases is the photo electro-method, because there is a synergy between the oxidizing power of electro- Fenton method and the degradation capacity of ultraviolet radiation on some degradation intermediates. The study also comprises a tracking of all intermediates generated during mineralization by spectrophotometric and chromatographic techniques , and a kinetic study for every herbicide . Finally a degradation pathway is proposed for the three herbicides consistent with experimental results.RESUMEN: Los procesos de oxidación avanzada son hoy en día, un tratamiento efectivo para la eliminación de contaminantes persistentes de las aguas residuales, a la vez que son medioambientalmente compatibles. En la presente tesis doctoral se ha hecho el estudio de la degradación de tres herbicidas s-triazínicos, la atrazina, la desmetrina y la cianacina, de uso habitual para el tratamiento de cultivos, para eliminar las malas hierbas que hacen disminuir la producción en plantaciones de carácter extensivo. Los tratamientos aplicados se basan en procesos de oxidación en celda electrolítica con un ánodo de diamante dopado con boro (BDD) y un cátodo de acero inoxidable o de difusión de oxígeno. El ánodo de BDD se ha mostrado muy eficaz para esta finalidad puesto que posee una elevada resistencia en diversos medios y posee un elevado sobrepotencial al desprendimiento de oxígeno. Las condiciones estudiadas para la degradación se han efectuado teniendo en cuenta la influencia del pH de medio, la temperatura y la presencia de catalizadores. Los métodos aplicados han sido la oxidación anódica, electro-Fenton y foto electro-Fenton. En al caso de los tratamientos Fenton, el peróxido de hidrógeno necesario para que tenga lugar la reacción de Fenton se ha electrogenerado con un cátodo de difusión de aire. En el método foto electro-Fenton, se irradió la solución a tratar con una lámpara UV de luz negra. Los resultados obtenidos demuestran que el tratamiento más eficaz es en todos los casos el método foto electro-Fenton, por existir una sinergia entre el poder oxidante del método electro-Fenton y la capacidad degradativa de la radiación ultravioleta sobre ciertos intermedios de degradación generados. El estudio comprende un seguimiento de todos los intermedios generados durante la mineralización mediante técnicas cromatográficas y espectrofotométricas, así como un estudio cinético para cada uno de los compuestos estudios, siguiendo todos ellos cinéticas de pseudo primer orden. Finalmente se ha propuesto un camino de degradación para los tres herbicidas coherente con los resultados experimentales obtenidos

Interface porosity in multilayered all-conducting polymer electrodes

Multilayered films made with at least two different electroactive polymers, in which the least conducting one acts as a dielectric and separates the layers made with the other, behave as efficient electrodes for electrochemical supercapacitors. In this work, we present a simple strategy to develop improved multilayered electrodes with structured interfaces by enhancing the porosity of the dielectric. This has been achieved by growing sodium chloride crystals onto a conducting polymer layer and, after generation of all required layers using the layer-by-layer electrodeposition technique, salt crystals have been eliminated by water etching. Results from morphological and topographical studies on single-layered poly(3,4-ethylenedioxythiophene) (PEDOT), poly(N-methylpyrrole) (PNMPy), and poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (COP), as well as electrochemical investigations on bi-layered films with enhanced porosity at the interface between the two layers, have been used to design new four-layered electrodes. These consist in two layers of PEDOT separated by two layers of nanosegregated COP with a porous interface in the middle. Although the properties of the new four-layered electrodes improve due to the porous interface, the highest specific capacitance corresponds to the two-layered electrode in which two PEDOT layers are separated by an ultra-porous interface

Nanophase-segregation in the dielectric layer enhances the charge storage capacity of polymeric electrochemical supercapacitors

Properties related with the charge storage capacity have been evaluated for three-layered films made with two sheets of poly(3,4-ethylenedioxythiophene) separated by a sheet of poly(N-methylpyrrole) or poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (3l-PEDOT/PNMPy or 3l-PEDOT/P(EDOT-co-NMPy), respectively). The most distinctive trend of the copolymer, which shows electrochemical properties intermediate between those of the two homopolymers, is the formation of a biphasic structure, EDOT- and NMPy-rich blocks organizing separately. The ability to exchange charge reversibly is higher for 3l-PEDOT/P(EDOT-co-NMPy) than for 3l-PEDOT/PNMPy, the electroactivity and electrostability of such two 3-layered films being significantly better than that of single-layered PEDOT. Advantages of 3l-PEDOT/P(EDOT-co-NMPy) are mainly based on the nanophase-segregated structure of the copolymer. Thus, the intermediate layer can be considered as random disposition of ultrathin dielectrics having nanometric length and width. In terms of charge storage, the intermediate layer of 3l-PEDOT/P(EDOT-co-NMPy) can be viewed as a thin reservoir filled of heterogeneously distributed nanometric supercapacitors that are connected in series among them and in parallel to the PEDOT layers. The superiority of 3l-PEDOT/P(EDOT-co-NMPy) as organic electrochemical supercapacitor compared to other 3-layered systems, has been proved by powering a red LED bulb.Peer Reviewe

Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode

The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O2-diffusion cathode for H2O2 generation. The main oxidizing species are OH radicals formed at the BDD surface in all treatments and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF. A poor mineralization was attained using AO-H2O2 by the slow oxidation of persistent by-products with OH at the BDD surface. The synergistic action of OH in the bulk enhanced the degradation rate in EF, although almost total mineralization was only achieved in PEF due to the additional OH generation and photolysis of intermediates by UVA irradiation. The effect of current, pH and herbicide concentration on the mineralization degree and mineralization current efficiency of each EAOP was examined. Desmetryne decay always followed a pseudo first-order kinetics, being more rapidly destroyed in the sequence AO-H2O2 < EF < PEF. In all EAOPs, ammeline and cyanuric acid were identified as persistent heteroaromatic by-products and oxamic and formic acids were detected as generated carboxylic acids. The generation of cyanuric acid mainly by oxidation with OH at the BDD surface is the predominant path for desmetryne degradation. The initial nitrogen of desmetryne yielded NO 3 ion in low proportion and NHþ4 ion in much lesser extent, suggesting that its major part was lost as volatile N-derivatives.Peer ReviewedPostprint (published version

Degradation of atrazine by electrochemical advanced oxidation processes using a boron-doped diamond anode

Solutions of 30 mg L-1 of the herbicide atrazine have been degraded by environmentally friendly electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) using a small open and cylindrical cell with a boron-doped diamond (BDD) anode. AO has been carried out either with a stainless steel cathode or an O2 diffusion cathode able to generate H2O2. Hydroxyl radicals (•OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF are the main oxidants. All treatments yielded almost overall mineralization, although the rate for total organic carbon (TOC) removal is limited by the oxidation of persistent byproducts with •OH at the BDD surface. In AO, TOC abatement is enhanced by parallel electrochemical reduction of organics at the stainless steel cathode, while in PEF, it also increases from additional photolysis of intermediates by UVA light under the synergistic action of •OH in the bulk. The effect of current and pH on the degradative behavior of EAOPs has been examined to determine their optimum values. Atrazine decay always follows a pseudo-first-order reaction, being more rapidly destroyed from •OH in the bulk than at the BDD surface. Aromatic intermediates such as desethylatrazine, desethyldesisopropylatrazine, and cyanuric acid and short linear carboxylic acids such as formic, oxalic, and oxamic have been identified and quantified by reversed-phase and ion-exclusion HPLC, respectively. Released inorganic ions such as Cl-, NO3-, and NH4 + have been followed by ionic chromatography.Peer ReviewedPostprint (published version

Degradation of atrazine by electrochemical advanced oxidation processes using a boron-doped diamond anode

Solutions of 30 mg L-1 of the herbicide atrazine have been degraded by environmentally friendly electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) using a small open and cylindrical cell with a boron-doped diamond (BDD) anode. AO has been carried out either with a stainless steel cathode or an O2 diffusion cathode able to generate H2O2. Hydroxyl radicals (•OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF are the main oxidants. All treatments yielded almost overall mineralization, although the rate for total organic carbon (TOC) removal is limited by the oxidation of persistent byproducts with •OH at the BDD surface. In AO, TOC abatement is enhanced by parallel electrochemical reduction of organics at the stainless steel cathode, while in PEF, it also increases from additional photolysis of intermediates by UVA light under the synergistic action of •OH in the bulk. The effect of current and pH on the degradative behavior of EAOPs has been examined to determine their optimum values. Atrazine decay always follows a pseudo-first-order reaction, being more rapidly destroyed from •OH in the bulk than at the BDD surface. Aromatic intermediates such as desethylatrazine, desethyldesisopropylatrazine, and cyanuric acid and short linear carboxylic acids such as formic, oxalic, and oxamic have been identified and quantified by reversed-phase and ion-exclusion HPLC, respectively. Released inorganic ions such as Cl-, NO3-, and NH4 + have been followed by ionic chromatography.Peer Reviewe