Polyaniline/Montmorillonite Nanocomposites Obtained by In Situ Intercalation and Oxidative Polymerization in Cationic Modified-Clay (Sodium, Copper and Iron)

Polyaniline/montmorillonite nanocomposites (PANI/M) were obtained by intercalation of aniline monomer into M modified with different cations and subsequent oxidative polymerization of the aniline. The modified-clay was prepared by ion exchange of sodium, copper and iron cations in the clay (Na–M, Cu–M and Fe–M respectively). Infrared spectroscopy confirms the electrostatic interaction between the oxidized PANI and the negatively charged surface of the clay. X-ray diffraction analysis provides structural information of the prepared materials. The nanocomposites were characterized by transmission electron microscopy and their thermal degradation was investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites have higher thermal stability than pure PANI. The electrical conductivity of the nanocomposites increased between 12 and 24 times with respect to the pure M and this increase was dependent on the cation-modification. The electrochemical behavior of the polymers extracted from the nanocomposites was studied by cyclic voltammetry and a good electrochemical response was observed.This work was supported by the National Agency for the Development of University Research (ANDRU), the Directorate General of Scientific Research and Technological Development (DGRSDT) of Algeria. Ministerio de Economia y Competitividad and FEDER are also acknowledged (MAT2010-15273). The Generalitat Valenciana is also acknowledged (PROMETEO2013/038)

Electrodos de Diamante Dopado con Boro para el tratamiento electroquímico de aguas

Boron-doped diamond electrodes have emerged as anodic material due to their high physical, chemical and electrochemical stability. These characteristics make it particularly interesting for electrochemical wastewater treatments and especially due to its high overpotential for the Oxygen Evolution Reaction. Diamond electrodes present the maximum efficiency in pollutant removal in water, just limited by diffusion-controlled electrochemical kinetics. Results are presented for the elimination of benzoic acid and for the electrochemical treatment of synthetic tannery wastewater. The results indicate that diamond electrodes exhibit the best performance for the removal of total phenols, COD, TOC, and colour.Los electrodos de diamante dopados con boro han surgido como un nuevo material anódico debido a su propiedades como estabilidad física, química y electroquímica. Estas características hacen a estos electrodos especialmente interesantes para el tratamiento electroquímico de aguas residuales, debido sobre todo a su elevado sobrepotencial para la reacción de formación de oxígeno. Los electrodos de diamante presentan una eficiencia máxima para la eliminación de contaminantes en el agua, sólo limitada por la cinética del proceso electroquímico controlado por difusión. Se muestran algunos ejemplos como en la eliminación de ácido benzoico y en el tratamiento electroquímico de aguas sintéticas del curtido de pieles. Los resultados indican que los electrodos de diamante muestran el mejor rendimiento para la eliminación de fenoles, DQO, COT, y del color

Flexible ruthenium oxide-activated carbon cloth composites prepared by simple electrodeposition methods

This work focuses on the preparation of flexible ruthenium oxide containing activated carbon cloth by electrodeposition. Different electrodeposition methods have been used, including chronoamperometry, chronopotentiometry and cyclic voltammetry. The electrochemical properties of the obtained materials have been measured. The results show that the potentiostatic method allows preparing composites with higher specific capacitance than the pristine activated carbon cloth. The capacitance values measured by cyclic voltammetry at 10 mV s−1 and 1 V of potential window were up to 160 and 180 F g−1. This means an improvement of 82% and 100% with respect to the capacitance of the pristine activated carbon cloth. This excellent capacitance enhancement is attributed to the small particle size (4–5 nm) and the three-dimensional nanoporous network of the ruthenium oxide film which allows reaching very high degree of oxide utilization without blocking the pore structure of the activated carbon cloth. In addition, the electrodes maintain the mechanical properties of the carbon cloth and can be useful for flexible devices.Financial support by the Ministerio de Economía y Competitividad (MAT2010-15273) and Generalitat Valenciana and FEDER (PROMETEO/2009/047) projects are gratefully acknowledged. J.M.S. thanks Ministerio de Educación (SB2010-132)

Metal-free heteroatom-doped carbon-based catalysts for ORR. A critical assessment about the role of heteroatoms

Metal-free carbon-based catalysts have gained much attention during last years because of their interesting properties towards oxygen reduction reaction. Intrinsic parameters of carbon materials such as porosity, structural order, conductivity and defects have proved to have a strong influence in the catalytic activity of these materials. However, the highest differences in catalytic activity are obtained via doping with heteroatoms, being nitrogen the most remarkable in terms of activity and selectivity. One of the most challenging goals of the scientific community is to unravel the role of the functional groups in order to design an optimized material. However, the complexity of isolating one specific functionality, the difficult unambiguous characterization of the species and the influence of the intrinsic properties of the carbon materials, make the identification of the active sites a complex and controversial issue. This review presents a critical assessment about the role of heteroatoms on ORR from the analysis of the literature that combine both experimental work and computational modelling.The authors thank Ministerio de Ciencia, Innovación y Universidades and FEDER for financial support (Project RTI2018-095291-B-I00, ENE2017-90932-REDT and MAT2016-76595-R)

Few layers graphene-based electrocatalysts for ORR synthesized by electrochemical exfoliation methods

Graphene-based materials were synthesized by electrochemical exfoliation method (cathodic method) starting from a graphite sheet. In the established methodology, an initial immersion in H2SO4 was applied, followed by cathodic expansion in potassium sulphate, where the effect of the applied voltage was studied. Finally, by ultrasound treatment, the exfoliation was achieved to produce a dispersion of few layer graphene material. Once the optimum procedure was established, Pt nanoparticles were incorporated using H2PtCl6.6H2O. This incorporation was studied at each stage of the graphene-based material synthesis to determine which was the most adequate to obtain the highest Pt dispersion and the best distribution of the Pt nanoparticles. In this sense, the incorporation of Pt in the graphene-based material colloidal dispersion by stirring for 3 h and sonication for 1 h, results in Pt nanoparticles with an average size of around 1 nm with an excellent distribution in the carbon material. The performance of this catalyst was compared with the commercial Pt/C electrocatalyst, showing a great oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) activity, exceeding it by far when comparing the mass-specific activity (A gPt−1) In addition, it presents excellent stability and selectivity toward the 4-electron pathway in ORR, which is the most energy-efficient, and using half of the platinum loading compared to the commercial material.The authors would like to thank PID2019-105923RB-I00 and PID2021-123079OB-I00 projects funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, and the Generalitat Valenciana (GRISOLIA/2020/114) for the financial support

Polyaniline-Derived N-Doped Ordered Mesoporous Carbon Thin Films: Efficient Catalysts towards Oxygen Reduction Reaction

One of the most challenging targets in oxygen reduction reaction (ORR) electrocatalysts based on N-doped carbon materials is the control of the pore structure and obtaining nanostructured thin films that can easily be incorporated on the current collector. The carbonization of nitrogen-containing polymers and the heat treatment of a mixture of carbon materials and nitrogen precursor are the most common methods for obtaining N-doped carbon materials. However, in this synthetic protocols, the surface area and pore distribution are not controlled. This work enables the preparation of 2D-ordered N-doped carbon materials through the carbonization of 2D polyaniline. For that purpose, aniline has been electropolymerized within the porous structure of two different templates (ordered mesoporous Silica and ordered mesoporous Titania thin films). Thus, aniline has been impregnated into the porous structure and subsequently electropolymerized by means of chronoamperometry at constant potential. The resultant samples were heat-treated at 900 °C with the aim of obtaining 2D N-doped carbon materials within the template structures. Polyaniline and polyaniline-derived carbon materials have been analyzed via XPS and TEM and characterized by electrochemical measurements. It is worth noting that the obtained 2D-ordered mesoporous N-doped carbon materials have proved to be highly active electrocatalysts for the ORR because of the formation of quaternary nitrogen species during the heat treatment.This research was funded by Ministerio de Ciencia, Innovación y Universidades and FEDER grant number Project RTI2018-095291-B-I00 and ENE2017-90932-REDT

Reactive Insertion of PEDOT-PSS in SWCNT@Silica Composites and its Electrochemical Performance

Hybrid silica-modified materials were synthesized on glassy carbon (GC) electrodes by electroassisted deposition of sol-gel precursors. Single-wall carbon nanotubes (SWCNTs) were dispersed in a silica matrix (SWCNT@SiO2) to enhance the electrochemical performance of an inorganic matrix. The electrochemical behavior of the composite electrodes was tested against the ferrocene redox probe. The SWCNT@SiO2 presents an improvement in the electrochemical performance towards ferrocene. The heterogeneous rate constant of the SWCNT@SiO2 can be enhanced by the insertion of poly(3,4-Ethylendioxythiophene)-poly(sodium 4-styrenesulfonate) PEDOT-PSS within the silica matrix, and this composite was synthesized successfully by reactive electrochemical polymerization of the precursor EDOT in aqueous solution. The SWCNT@SiO2-PEDOT-PSS composite electrodes showed a heterogeneous rate constant more than three times higher than the electrode without conducting polymer. Similarly, the electroactive area was also enhanced to more than twice the area of SWCNT@SiO2-modified electrodes. The morphology of the sample films was analyzed by scanning electron microscopy (SEM).This research was funded by the Directorate General of Scientific Research and Technological Development (DGRSDT) (Algeria) and by the Ministerio de Ciencia, Innovación y Universidades (MAT2016-76595-R) and by the Conselleria de Educación, Investigación, Cultura y Deporte, Generalitat Valenciana (PROMETEO/2018/087)

Feasibility of electrochemical regeneration of activated carbon used in drinking water treatment plant. Reactor configuration design at a pilot scale

This work evaluates the feasibility of electrochemical regeneration of granular activated carbon used in drinking water treatment plants as a real alternative to thermal regeneration. Two pilot-plant-scale reactors, with a capacity of 10−15 kg, have been designed using two different configurations, parallel plate electrodes and concentric cylindrical electrodes. The optimization of the anode material has also been studied and Pt/Ti, RuO2/Ti and IrO2/Ti have been used. After the regeneration and, thus, recovery of the porosity the samples were tested in the adsorption of bisphenol A. In the electrochemical regeneration, recovery of the porosity of spent activated carbon until 100 % and 96 % with respect to the pristine activated carbon using Pt/Ti anode after 3 h of treatment, has been achieved. The regeneration process produces a small increase in the number of surface oxygen groups. No important differences have been observed among the tested anodes and RuO2/Ti and IrO2/Ti can be an economic alternative to Pt/Ti. Bisphenol A adsorption kinetics was slower in regenerated activated carbons probably due to the formation of surface oxygen groups. However, the adsorption capacity was similar in the regenerated samples and the pristine one.This work was supported by the European Union-Horizon 2020 (PORTABLECRAC - SPIRE09 - 2017 Nº 768905)

Tailoring Intrinsic Properties of Polyaniline by Functionalization with Phosphonic Groups

Phosphonated polyanilines were synthesized by copolymerization of aniline (ANI) with both 2- and 4-aminophenylphosphonic acids (APPA). The material composition and the final properties of the copolymers can be easily tailored by controlling the monomers ANI/APPA molar feed ratio. An important influence on the reactivity of monomers has been found with the substituent position in the ring, leading to differences in the properties and size of blocks of each monomer in the polymer. As expected, while 2APPA shows more similarities to ANI, 4APPA is much less reactive. Phosphorus loading of ~5 at% was achieved in the poly(aniline-co-2-aminophenylphosphonic acid) (PANI2APPA) with a 50/50 molar feed ratio. All the resulting copolymers were characterized by different techniques. Experimental results and density functional theory (DFT) computational calculations suggest that the presence of phosphonic groups in the polymeric chain gives rise to inter- and intra-chain interactions, as well as important steric effects, which induce a slight twist in the substituted PANI structure. Therefore, the physicochemical, electrical, and electrochemical properties are modified and can be suitably controlled.This research was funded by Ministerio de Ciencia e Innovación (Grant number: PID2019-105923RB-100) and Ministerio de Ciencia, Innovación y Universidades (grant number: FPU18/05127). And the APC was funded by Universidad de Alicante

Characterization and electrochemical properties of conducting nanocomposites synthesized from p-anisidine and aniline with titanium carbide by chemical oxidative method

A novel polymer/TiC nanocomposites “PPA/TiC, poly(PA-co-ANI)/TiC and PANI/TiC” was successfully synthesized by chemical oxidation polymerization at room temperature using p-anisidine and/or aniline monomers and titanium carbide (TiC) in the presence of hydrochloric acid as a dopant with ammonium persulfate as oxidant. These nanocomposites obtained were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA). XRD indicated the presence of interactions between polymers and TiC nanoparticle and the TGA revealed that the TiC nanoparticles improve the thermal stability of the polymers. The electrical conductivity of nanocomposites is in the range of 0.079–0.91 S cm−1. The electrochemical behavior of the polymers extracted from the nanocomposites has been analyzed by cyclic voltammetry. Good electrochemical response has been observed for polymer films; the observed redox processes indicate that the polymerisation on TiC nanoparticles produces electroactive polymers. These nanocomposite microspheres can potentially used in commercial applications as fillers for antistatic and anticorrosion coatings.This work was supported by the National Assessment and Planning Committee of the University Research (CNEPRU), and the Directorate General of Scientific Research and Technological Development (DGRSDT) of Algeria. Financial support from the Generalitat Valenciana (PROMETEO2013/038) is acknowledged