Scanning electrochemical microscopy for the analysis and patterning of graphene materials: A review

[EN] Graphene and related materials have recently emerged as outstanding materials due to a range of properties such as high mechanical strength, high electron mobility, thermal conductivity, etc. Due to their high surface area and conductivity, graphene materials have also been used for electrochemical applications such as supercapacitors, batteries, sensors, etc. Therefore, the characterization of the electroactivity of graphene materials is necessary and different electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy have been widely used for this purpose. Scanning electrochemical microscopy has appeared as a unique technique that can be used to test electron transfer kinetics, electroactivity and conductivity of these materials. Even patterns can be created on graphene materials by this technique, This review aims to compile the different works performed with graphene materials and scanning electrochemical microscopy technique and provide new perspectives into the analysis of graphene materials using this technique. (C) 2016 Elsevier B.V. All rights reserved.Authors wish to thank to the Spanish Ministerio de Ciencia e Innovacion (contract MAT2016-77742-C2-1-P) 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). Tim Vickers is gratefully acknowledged for help with the English revision.Molina Puerto, J.; Fernández Sáez, J.; Cases Iborra, FJ. (2016). Scanning electrochemical microscopy for the analysis and patterning of graphene materials: A review. Synthetic Metals. 222:145-161. https://doi.org/10.1016/j.synthmet.2016.10.019S14516122

Cooperativas, sociedades laborales y mutualidades de previsión social: 25 años de progreso de la economía social de mercado bajo la constitución de 1978

This paper analyses the evolution of the leading market social economy organisations in Spain since the Constitution of 1978. The first part concerns a study of co-operatives and workers societies; the second refers to mutual societies. An analysis of the institutional framework, this sector's quantitative evolution, the responses to changes in the business background and the social impact of their activities enable us to conclude that over the period studied these companies have very significantly reinforced their position in the market. At the same time, they have consolidated their institutional recognition and their social image. Nevertheless, this very positive result should not obscure certain structural problems limiting their potential for development. The fragmentation of the three sub-sectors examined and the differences in legal treatment in financial and tax matters affecting mutual societies are questions that have to be resolved over coming years, with the aim of improving the competitive position of these organisations.co-operatives, worker associations, mutual societies, market social economy.

Determinants of bank efficiency: evidence from the Latin American banking industry

Purpose: The purpose of this paper is to analyze a variety of factors that can explain the differences in commercial bank efficiency among 17 countries in Latin America (LatAm). Design/methodology/approach: In a first stage, data envelopment analysis (DEA) and conditional efficiency analysis techniques are used to assess the relative efficiency level of 409 banks for the 2014-2016 period. The conditional efficiency approach considers environmental variables (that are beyond the manager’s control), which could influence the shape and the level of the boundary of the attainable set. In the second stage, the resulting conditional efficiency scores are correlated with internal variables (those that are under the manager’s control), which might affect the distribution of the inefficiencies. For this purpose, an econometric approach developed by Simar and Wilson (2007) is used. Findings: First stage scores reveal the heterogeneity of average efficiency within the region. Regarding the factors that may explain the differences in performance in the LatAm banking sector, the results allow us to state that certain internal variables such as bank size, the ratio of loans to total assets and the ratio of non-performing loans show the expected relationship to efficiency, in line with much of the previous literature. Originality/value: This is the first time that conditional efficiency and Simar and Wilson (2007) approaches have been applied at the same time to analyse the LatAm banking industry.Fil: Jiménez Hernandez, Ignacio. Universidad de Granada; EspañaFil: Palazzo, Gabriel Martín. Centro de Estudios de Estado y Sociedad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Económicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sáez Fernández, Francisco Javier. Universidad de Granada; Españ

Performance and risk in the Brazilian banking industry

Andres J. Picazo-Tadeo aknowledges the financial support from the Generalitat Valenciana (project PROMETEO 2018/102).This paper assesses the technical performance of Brazilian banks while accounting for risk, which is considered as an undesirable outcome of banking. To this end, frontier techniques based on Data Envelopment Analysis and directional distance functions are applied to a sample of 124 banks and data for the six-year period 2014-19. Our main finding is that the Brazilian banking industry could notably increase its production of conventional outputs without additional input usage and while maintaining the same levels of risk. Besides, investment banks are found to be more efficient than commercial banks mainly because of their superior managerial performance.Generalitat Valenciana European Commission PROMETEO 2018/10

Enhancement of the Electrochemical Properties of an Open-Pore Graphite Foam with Electrochemically Reduced Graphene Oxide and Alternating Current Dispersed Platinum Particles

[EN] This paper aimed to improve the electrochemical activity of a pitch-derived open-pore graphite foam (GF) by an electrochemical coating of reduced graphene oxide (RGO) and platinum particles without significantly affecting its 3D-structure. RGO was synthesized using cyclic voltammetry (CV) from a 3 g L(-1)GO and 0.1 M LiClO(4)solution. For the electrodeposition of Pt particles, an alternating current method based on electrochemical impedance spectroscopy (EIS) was used. A sinusoidal voltage from a fixed potential Ei was varied following a selected amplitude (Delta E-ac= +/- 0.35 V) in a frequency range of 8 Hz <= f(i)<= 10Hz, wherei= 500. This method proved its efficiency when compared to the traditional CV by obtaining more highly electroactive coatings in less synthesis time. For samples' characterization, physical measures included permeability, pressure drop, and nitrogen adsorption isotherms. The electrochemical characterization was performed by CV. The surface morphology and chemical composition were examined using field emission electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. RGO improved the electron transfer rate constant of GF, and a more homogeneous coating distribution of reduced size Pt particles was obtained.This research was funded by the Spanish Agencia Estatal de Investigación (AEI) and the European Union (FEDER funds) contracts (MAT2016-77742-C2-1-P, MAT2016-77742-C2-2-P). Financial support of Network E3TECH (CTQ2017-90659-REDT) is acknowledged.Fernández Sáez, J.; Bonastre Cano, JA.; Molina, JM.; Cases, F. (2020). Enhancement of the Electrochemical Properties of an Open-Pore Graphite Foam with Electrochemically Reduced Graphene Oxide and Alternating Current Dispersed Platinum Particles. Coatings. 10(6):1-12. https://doi.org/10.3390/coatings10060551S112106Prieto, R., Louis, E., & Molina, J. M. (2012). Fabrication of mesophase pitch-derived open-pore carbon foams by replication processing. Carbon, 50(5), 1904-1912. doi:10.1016/j.carbon.2011.12.041Molina-Jordá, J. M. (2016). Mesophase pitch-derived graphite foams with selective distribution of TiC nanoparticles for catalytic applications. Carbon, 103, 5-8. doi:10.1016/j.carbon.2016.02.051Lai, J., Nsabimana, A., Luque, R., & Xu, G. (2018). 3D Porous Carbonaceous Electrodes for Electrocatalytic Applications. Joule, 2(1), 76-93. doi:10.1016/j.joule.2017.10.005Morozov, S. V., Novoselov, K. S., Katsnelson, M. I., Schedin, F., Elias, D. C., Jaszczak, J. A., & Geim, A. K. (2008). Giant Intrinsic Carrier Mobilities in Graphene and Its Bilayer. Physical Review Letters, 100(1). doi:10.1103/physrevlett.100.016602Singh, V., Joung, D., Zhai, L., Das, S., Khondaker, S. I., & Seal, S. (2011). Graphene based materials: Past, present and future. Progress in Materials Science, 56(8), 1178-1271. doi:10.1016/j.pmatsci.2011.03.003Zhou, M., Wang, Y., Zhai, Y., Zhai, J., Ren, W., Wang, F., & Dong, S. (2009). Controlled Synthesis of Large-Area and Patterned Electrochemically Reduced Graphene Oxide Films. Chemistry - A European Journal, 15(25), 6116-6120. doi:10.1002/chem.200900596Bonanni, A., & Pumera, M. (2012). Electroactivity of graphene oxide on different substrates. RSC Advances, 2(28), 10575. doi:10.1039/c2ra22079bZhong, M., Song, Y., Li, Y., Ma, C., Zhai, X., Shi, J., … Liu, L. (2012). Effect of reduced graphene oxide on the properties of an activated carbon cloth/polyaniline flexible electrode for supercapacitor application. Journal of Power Sources, 217, 6-12. doi:10.1016/j.jpowsour.2012.05.086Yoo, E., Okata, T., Akita, T., Kohyama, M., Nakamura, J., & Honma, I. (2009). Enhanced Electrocatalytic Activity of Pt Subnanoclusters on Graphene Nanosheet Surface. Nano Letters, 9(6), 2255-2259. doi:10.1021/nl900397tKundu, P., Nethravathi, C., Deshpande, P. A., Rajamathi, M., Madras, G., & Ravishankar, N. (2011). Ultrafast Microwave-Assisted Route to Surfactant-Free Ultrafine Pt Nanoparticles on Graphene: Synergistic Co-reduction Mechanism and High Catalytic Activity. Chemistry of Materials, 23(11), 2772-2780. doi:10.1021/cm200329aXin, Y., Liu, J., Zhou, Y., Liu, W., Gao, J., Xie, Y., … Zou, Z. (2011). Preparation and characterization of Pt supported on graphene with enhanced electrocatalytic activity in fuel cell. Journal of Power Sources, 196(3), 1012-1018. doi:10.1016/j.jpowsour.2010.08.051Zhang, Y., Liu, C., Min, Y., Qi, X., & Ben, X. (2013). The simple preparation of graphene/Pt nanoparticles composites and their electrochemical performance. Journal of Materials Science: Materials in Electronics, 24(9), 3244-3248. doi:10.1007/s10854-013-1235-xProducts: Chemically Modified Graphene Oxidehttps://www.nanoinnova.com/product/chemically-modified-g

Seasonality and Efficiency of the Hotel Industry in the Balearic Islands: Implications for Economic and Environmental Sustainability

Tourism seasonality generates negative environmental and economic impacts. This paper analyzes the effects of seasonality on the efficiency of the hotel industry in the Balearic Islands (Spain). To that end, a sample of hotel establishments is divided into two groups (those that close down during the off-season and those that do not). Data envelopment analysis (DEA) is applied to assess the radial efficiency of each of the selected hotels; then, directional distance functions (DDFs) are used to measure the degree of efficiency with which these hotels use each of the inputs that form part of their production process. To the best of our knowledge, this is the first time that the said technique has been applied to the hospitality industry to examine the effects of seasonality. The results of this study suggest that those establishments that do not close down their operations are markedly more efficient than the ones that do. Moreover, they are more efficient in the use of each input. Therefore, a reduction in the levels of tourism seasonality would improve the economic sustainability of the hotels and reduce the environmental pressure at peak times. Finally, in line with the theoretical hypotheses formulated, the results regarding the specific efficiency levels for each input show that the greater the degree of flexibility with which these inputs are used, the higher the efficiency

Study on the specific capacitance of an activated carbon cloth modified with reduced graphene oxide and polyaniline by cyclic voltammetry

This work describes a two-step process for the electrochemical coating of reduced graphene oxide (RGO) and polyaniline (PANI) onto an activated carbon cloth (ACC) by cyclic voltammetry (CV). The fact that the two syntheses are carried out independently of each other, makes it possible to select the experimental conditions for each one and to study the electrochemical response of RGO, PANI, and PANI onto RGO (RGOPANI), separately. Thus, by modifying the potential limits of the aniline-polymerization reaction, it was possible to observe the influence of RGO and the maximum amount of PANI that the carbon cloth can receive in terms of proper electrochemical response. Electrochemical properties were characterized by CV, galvanostatic charge-discharge curves (using three or two-electrodes symmetric cell configurations) and electrochemical impedance spectroscopy (EIS). A maximum improvement of 25%, 56% and 61% over the initial specific capacitance of ACC (about 129 F g−1) were obtained for RGO, PANI and RGOPANI coatings, respectively. Good cycling stability retaining 83% of the initial capacitance, after 1000 cycles stability test, was obtained for RGOPANI sample. Promising results of energy and power densities were also achieved. In the analyses by Fourier transform infrared spectroscopy (FTIR), the PANI-bands could be clearly identified which is indicative of a significant presence of PANI. Field emission scanning electron microscopy (FESEM) showed the morphology of RGO, PANI and RGOPANI onto the ACC fibers. These analyses helped to explain the electrochemical results.The authors wish to acknowledge to Chemviron Carbon who kindly donated the ZORFLEX (R) activated carbon fabric. The authors wish to thank the Spanish Agenda Estatal de Investigacion (AEI) and European Union (FEDER funds) for the financial support (contract MAT2016-77742-C2-1-P). Tim Vickers is gratefully acknowledged for help with the English revision.Fernández Sáez, J.; Bonastre Cano, JA.; Molina Puerto, J.; Del Río García, AI.; Cases Iborra, FJ. (2017). Study on the specific capacitance of an activated carbon cloth modified with reduced graphene oxide and polyaniline by cyclic voltammetry. European Polymer Journal. 92:194-203. doi:10.1016/j.eurpolymj.2017.04.044S1942039

Chemical, electrical and electrochemical characterization of hybrid organic/inorganic polypyrrole/PW12O403- coating deposited on polyester fabrics

A study of the stability of conducting fabrics of polyester (PES) coated with polypyrrole/PW12O403¿ (organic/inorganic hybrid material) in different pH solutions (1, 7, 13) has been done. Washing tests were also done in views of its possible application in electronic textiles such as antistatic clothing. X-ray photoelectron spectroscopy (XPS) studies have been done to quantify the amount of counter ion that remains in the polymer matrix and determine the doping ratio (N+/N) after the different tests. Scanning electron microscopy (SEM) was also used to observe morphological differences after the different tests. Surface resistivity changes were measured by means of electrochemical impedance spectroscopy (EIS). Scanning electrochemical microscopy (SECM) was employed to measure changes in electroactivity after the different tests. Higher pHs caused a decrease of the doping ratio (N+/N), the loss of part of the counter ions and the decrease of its conducting and electrocatalytic properties. The stability in acid media and neutral media and after the washing test was good. Only at pH 13 the loss of the counter ion was widespread and there was a decrease of its conducting and catalytic properties; although the fabrics continued acting mainly as a conducting material.Authors thank the Spanish Ministerio de Ciencia y Tecnologia, European Union Funds (FEDER) (contract CTM2007-66570-C02-02) and Universitat Politecnica de Valencia (Programa de apoyo a la investigacion y desarrollo de la UPV (PAID-05-08)) 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. (2011). Chemical, electrical and electrochemical characterization of hybrid organic/inorganic polypyrrole/PW12O403- coating deposited on polyester fabrics. Applied Surface Science. 257:10056-10064. doi:10.1016/j.apsusc.2011.06.140S100561006425

Electrochemical synthesis of polyaniline on conducting fabrics of polyester covered with polypyrrole/PW12O403-. Chemical and electrochemical characterization

Polyaniline (Pani) has been electrochemically polymerized on conducting fabrics of polyester covered with polypyrrole/PW 12O 40 3-, obtaining a double conducting polymer layer. Electrochemical synthesis was performed by potentiostatic synthesis at 1 V. The chemical characterization of the material before and after Pani polymerization was performed by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of the coatings was observed employing scanning electron microscopy (SEM). The electrochemical characterization was performed by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). It has been demonstrated that scan rate is an important parameter that influences the response obtained when characterizing conducting fabrics by CV. High scan rates do not allow the observation of redox peaks. However if lower scan rates are employed its apparition has been reported. The electrochemical deposit of polyaniline enhances the electroactivity of the material as it has been demonstrated by CV. SECM measurements showed local response with positive feedback (electroactive material) for the samples in open circuit conditions. XPS analysis also showed a higher doping level (N +/N), consistent with higher material electroactivity. © 2011 Elsevier B.V.Authors thank to the Spanish Ministerio de Ciencia y Tecnologia and European Union Funds (FEDER) (contract CTM2007-66570-C02-02 and CTM2010-18842-C02-02) and Universidad Politecnica de Valencia (Primeros Proyectos de Investigacion (PAID-06-10)) 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. (2011). Electrochemical synthesis of polyaniline on conducting fabrics of polyester covered with polypyrrole/PW12O403-. Chemical and electrochemical characterization. Synthetic Metals. 161(11-12):953-963. doi:10.1016/j.synthmet.2011.02.029S95396316111-1

Electrochemical treatment of solutions containing a recalcitrant dye: A way of using dimensionally adaptable catalytic fabrics

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Industrial and Engineering Chemistry Research, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.iecr.5b00590The objective of this work is to study the decolorization/degradation of reactive dye Remazol Black (RMZB) in sulfuric media. The electrochemical behavior was evaluated by cyclic voltammetry (CV) using platinum (Pt) and glassy carbon (GC) as working electrodes. Different electrolyses were performed potentioscally using Pt, activated carbon textile (ACT) and activated carbon textile electrocatalytically improved with dispersed Pt (Pt-ACT) with and without NaCl. The decolorization was studied by UV-visible spectroscopy. High performance liquid chromatography (HPLC) also permitted us to confirm the dye degradation. Specific applied charge (Q/Ah L-1) was evaluated and the efficiencies of the dye degradation were discussed in terms of electrical energy per order (E-EO/kWh m(-3) order(-1)). Field emission scanning electron microscopy (FESEM) was used to observe the morphological differences of a Pt-ACT electrode before and after the electrolyses, confirming that the corverage of dispersed Pt remains on the surface.The authors thank 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. A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for her FPI fellowship. J. Molina is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for the Program VALi+D Postdoctoral Fellowship. C. Garcia is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for her Geronimo Forteza fellowship.Del Río García, AI.; García, C.; Fernández Sáez, J.; Molina Puerto, J.; Bonastre Cano, JA.; Cases Iborra, FJ. (2015). Electrochemical treatment of solutions containing a recalcitrant dye: A way of using dimensionally adaptable catalytic fabrics. Industrial and engineering chemistry research. 54(25):6418-6429. https://doi.org/10.1021/acs.iecr.5b00590S64186429542