Electrochemical synthesis of polypyrrole doped with graphene oxide and its electrochemical characterization as membrane material

Polypyrrole (PPy) doped with graphene oxide (GO) has been electrochemically obtained by potentiostatic synthesis and its electrochemical behavior as membrane material has been studied for the first time. Fourier transform infrared spectroscopy with attenuated total reflection showed the formation of the hybrid material due to presence of PPy and GO bands. Field emission scanning electron microscopy micrographs showed the effective incorporation of GO sheets and the formation of a 3-D porous material with high surface area. Scanning electrochemical microscopy of PPy/GO films showed positive feedback close to the ideal conducting behavior, indicating a good electroactivity. Electrochemical impedance spectroscopy (EIS) was employed to measure the electrochemical properties of the coatings by two-, three-, and four-electrode configurations. The electronic conductivity of PPy/GO film, measured between two metallic conductors, was 4.7·10−6 S/cm. Its ionic conductivity was superior (1.6·10−3 S/cm) due to the high porosity of the material as demonstrated by cyclic voltammetry and EIS measurements, where the PPy/GO film was employed as a free-standing membrane. The diffusion-migration rate of tetramethylammonium chloride was very similar to sodium chloride when present in the same concentration, which indicated no influence of the size of the electrolyte conductor due to the high porosity. © 2016 Elsevier B.V. All rights reserved.Authors wish to thank the Spanish Ministerio de Ciencia e Innovacion (contract CTM2011-23583) for the financial support. J. Molina is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for the Programa VALi+D Postdoctoral Fellowship (APOSTD/2013/056). A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for her FPI fellowship. Electron Microscopy Service of the UPV (Universitat Politecnica de Valencia) is gratefully acknowledged for help with FESEM and EDX characterization.Molina Puerto, J.; Bonastre Cano, JA.; Fernández Sáez, J.; Del Río García, AI.; Cases Iborra, FJ. (2016). Electrochemical synthesis of polypyrrole doped with graphene oxide and its electrochemical characterization as membrane material. Synthetic Metals. 220:300-310. https://doi.org/10.1016/j.synthmet.2016.06.028S30031022

Chemical and electrochemical study of fabrics coated with reduced graphene oxide

Polyester fabrics coated with reduced graphene oxide (RGO) have been obtained and later characterized by means of chemical and electrochemical techniques. X-ray photoelectron spectroscopy showed a decrease of the oxygen content as well as an increase of the sp2 fraction after chemical reduction of graphene oxide (GO). The electrical conductivity was measured by electrochemical impedance spectroscopy (EIS) and showed a decrease of 5 orders of magnitude in the resistance (¿) when GO was reduced to RGO. The phase angle also changed from 90° for PES-GO (capacitative behavior) to 0° for RGO coated fabrics (resistive behavior). In general an increase in the number of RGO layers produced an increase of the conductivity of the fabrics. EIS measurements in metal/sample/electrolyte configuration showed better electrocatalytic properties and faster diffusion rate for RGO specimens. Scanning electrochemical microscopy was employed to test the electroactivity of the different fabrics obtained. The sample coated with GO was not conductive since negative feedback was obtained. When GO was reduced to RGO the sample behaved like a conducting material since positive feedback was obtained. Approach curves indicated that the redox mediator had influence on the electrochemical response. The Fe(CN)63¿/4¿ redox mediator produced a higher electrochemical response than Ru(NH3)63+/2+ one.Authors thank to the Spanish Ministerio de Ciencia e Innovacion (contract CTM2011-23583) and Universitat Politecnica de Valencia (Vicerrectorado de Investigacion PAID-06-10 contract 003-233) for the financial support. J. Molina is grateful to the Conselleria d'Educacio (Generalitat Valenciana) for the FPI fellowship. A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for the FPI fellowship. J.C. Galvan is gratefully acknowledged for help with EIS measurements and data analysis.Molina Puerto, J.; Fernández Sáez, J.; Del Río García, AI.; Bonastre Cano, JA.; Cases Iborra, FJ. (2013). Chemical and electrochemical study of fabrics coated with reduced graphene oxide. Applied Surface Science. 279:46-54. https://doi.org/10.1016/j.apsusc.2013.04.020S465427

Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes

The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300 ¿g cm -2 was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt-Pani-Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion. © 2012 Elsevier B.V.Authors thank to the Spanish Ministerio de Ciencia e Innovacion and European Union Funds (FEDER) (contracts CTM2010-18842-C02-02 and CTM2011-23583) and Universitat Politecnica de Valencia (Vicerrectorado de Investigacion PAID-06-10 contract 003-233) for the financial support. J. Molina is grateful to the Conselleria d'Educacio (Generalitat Valenciana) for the FPI fellowship. A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for the FPI fellowship.Molina Puerto, J.; Fernández Sáez, J.; Del Río García, AI.; Bonastre Cano, JA.; Cases Iborra, FJ. (2012). Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes. Applied Surface Science. 258:6246-6256. doi:10.1016/j.apsusc.2012.02.150S6246625625

Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods

Reduced graphene oxide (RGO) has been synthesized on Pt wires by means of a potentiodynamic method between +0.6 V and -1.4'V for 20 scans. Cyclic voltammetry characterization of the coatings showed the typical capacitative behavior of graphene. Pt nanoparticles were synthesized on Pt-RGO electrodes by means of potentiostatic methods and a comparison between different synthesis potentials (-0.16, 0, +0.2 and +0.4 V) for the same synthesis charge (mC.cm(-2)) was established. The electrodes obtained were characterized in 0.5 M H2SO4 solution to observe the characteristic oxidation and reduction processes of the Pt surface. A 0.5 M H2SO4/0.5 M CH3OH solution was used to measure the catalytic properties of the deposits against methanol oxidation. The most appropriate potential to perform the synthesis was 0 V followed by -0.16 V and +0.2 V. The morphology of the coatings varied depending on the potential applied as observed by scanning electron microscopy. Alternate current methods were also used to synthesize Pt nanoparticles and compare the results with the traditional potentiostatic method. Different frequencies were used: 0.1, 1, 10, 100, 1000 and 10000 Hz. Alternate current synthesis is more efficient than traditional potentiostatic methods, obtaining more electroactive coatings with less effective synthesis time. (C) 2014 Elsevier Inc. All rights reserved.Authors wish to thank to the Spanish Ministerio de Ciencia e Innovacion (contract CTM2011-23583) and Universitat Politecnica de Valencia (Vicerrectorado de Investigacion PAID-06-10 contract 003-233) for the financial support. J. Molina is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for the Programa VALi+D Postdoctoral Fellowship. A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for the FPI fellowship.Molina Puerto, J.; Fernández Sáez, J.; Del Río García, AI.; Bonastre Cano, JA.; Cases Iborra, FJ. (2014). Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods. Materials Characterization. 89:56-68. https://doi.org/10.1016/j.matchar.2014.01.003S56688

Study of the electrical properties of novel hybrid organic-inorganic conducting textiles of polypyrrole-phosphotungstate-polyester using electrochemical impedance spectroscopy

The electrical properties of novel hybrid organic-inorganic conducting fabrics of polyester (PES) coated with polypyrrole-PW12O 40 3- (PPy-POM) have been tested for dry samples and specimens immersed in different pH solutions (1, 7, and 13). Electrical properties changes were measured by means of electrochemical impedance spectroscopy (EIS). This study showed that organic-inorganic PES-PPy-POM conducting textiles act as electronic conductors with semiconducting nature. The electrical conductivity was measured for different temperatures and a value of 44.4 meV was obtained for the activation energy by means of Arrhenius model. Samples immersed in solution increased their conductivity in more acid solutions due to polypyrrole protonation. As acidity increased protonation and oxidation state of polypyrrole chains increased, and a greater diffusion of counter-ions was observed since the hybrid conducting textiles presented a more swollen and porous structure. Counter-ion exchange was higher in more acid solutions since more charge was needed to compensate the positive charge of more oxidized polypyrrole chains. A catalytic effect might be expected for the H+ reduction for this new organic-inorganic electrode material in acid media. © 2011 Elsevier B.V. All rights reserved.Peer Reviewe

Rh-mediated C1-polymerization: copolymers from diazoesters and sulfoxonium ylides

In this paper, we present new results obtained in our investigations of Rh-catalyzed C1 (co)polymerization reactions using carbene units as monomers. We demonstrate here, for the first time, the use of transition metal catalysts in carbene polymerization using sulfur ylides as the carbene monomer precursors. Furthermore, we show that it is possible to generate unique diblock copolymers from sulfoxonium ylides and diazoesters as the respective carbene monomer precursors. This constitutes an entirely new approach to the synthesis of functional copolymers. The copolymerization reactions were successful, and high-Mw poly(methylene)-poly(ester carbene) copolymers were obtained with a diblock-syndiotactic microstructure in decent yields. These copolymers can be used as blending agents to mix polyethylene or polymethylene with poly(ethyl 2-ylidene-acetate). The copolymer properties are highly dependent on the functional-group content. Model studies and investigations on the influence of the catalyst structure on the obtained polymer yields provide insights into the catalyst activation and deactivation processes operative under the applied reaction conditions

Influence of cell design and electrode materials on the decolouration of dyeing effluents

Electrochemical techniques are applied in different textile processes, including wastewater treatment, as they are clean and generally operate at room temperature. In the current work, doped SnO2 electrodes (Ti/SnO2-Sb-Pt) were prepared. They were used as anodes in two electrochemical cells (simple batch mode and batch recirculation mode) to achieve the removal of two reactive azo dyes (Remazol Black 133B and Procion Yellow H-EXL) in synthetic dyeing effluents. With these electrodes, both cells exhibit similar decolouration rates. In addition, the doped SnO2 electrodes are compared with Ti/Pt electrodes in order to establish the influence of electrode material. They were applied to the treatment of four synthetic effluents containing one of the following reactive azo dyes: Remazol Black 133B, Procion Yellow H-EXL, Procion Crimson H-EXL and Procion Navy H-EXL. It was stated that the decolouration is faster with Ti/Pt anodes than with the doped SnO2 ones, but these last electrodes generate lower amount of chloroform during the electrolysi

Electrochemical treatment of a synthetic wastewater containing a sulphonated azo dye. Determination of naphthalenesulphonic compunds produced as main by-products

The electrochemical treatment of wastewaters from textile industry is a promising technique for substances which are resistant to biodegradation. This paper deals with the electrochemical decolourisation/degradation of synthetic solutions containing a reactive dye, C.I. Reactive Orange 4. Oxidation, reduction and oxido-reduction processes were evaluated using Ti/SnO 2-Sb-Pt and stainless steel electrodes as anode and cathode, respectively. Electrolyses were performed at galvanostatic conditions in a filter press reactor. Decolourisation and degradation were followed by means of total organic carbon (TOC), chemical oxygen demand (COD) measurements and high performance liquid chromatography (HPLC). A higher mineralisation rate for oxidation was found whilst oxido-reduction process gave more oxidised species. The kinetics of decolourisation was of pseudo-first order in all cases. The reduction process was the slowest process to decolourise. Gas chromatography-mass spectrometry (GC-MS) was employed to investigate the main intermediate compounds, confirming the presence of 2-amino-1, 5-naphthalenedisulphonic acid (2A15NDS) in solution. When this compound was generated, it was gradually degraded during the oxidation and oxido-reduction processes indicating the feasibility and durability of Ti/SnO 2-Sb-Pt electrodes. However, during the electrochemical reduction process, this compound was continuously generated but it was not degraded. © 2011 Elsevier B.V.The authors would like to acknowledge the Spanish Ministry of Science and Innovation (MICINN) and European Union (FEDER funds) for the financial support (CTM2007-66570-C02-02 and CTM2010-18842-C02-02). A. I. del Rio thanks the Spanish Ministry of Science and Innovation (MICINN) for her F.P.I. grant awarding. J. Molina is grateful to the Conselleria d'Educacio (Generalitat Valenciana) for his FPI grant awarding.Del Río García, AI.; Fernández Sáez, J.; Molina Puerto, J.; Bonastre Cano, JA.; Cases Iborra, FJ. (2011). Electrochemical treatment of a synthetic wastewater containing a sulphonated azo dye. Determination of naphthalenesulphonic compunds produced as main by-products. Desalination. 273(2-3):428-435. doi:10.1016/j.desal.2011.01.070S4284352732-