0000000000222376
AUTHOR
Vicente Compañ
showing 27 related works from this author
Thermodynamics of electrokinetic processes—II. systems with different kinds of electrodes
1990
Abstract In this work Haase's Formulation of Electrokinetic Processes is applied to special systems: those working with two different electrodes and those where gaseous phases are formed. Phenomenological equations are always written in terms of directly observable variables. The extrinsic character of Haase's Formulation is clearly shown. Some special results on streaming current in dielectric liquids are explained.
Proton conductivity through polybenzimidazole composite membranes containing silica nanofiber mats
2019
The quest for sustainable and more efficient energy-converting devices has been the focus of researchers&prime
Determination of the oxygen transmissibility and permeability of hydrogel contact lenses
1999
To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permeability and transmissibility coefficients of the lenses, the coefficients of one low hydration (38% water) and two high hydration (55 and 58% water) hydrogel contact lenses stacked one to five on an oxygen electrode were deter- mined. From the oxygen diffusion through the lenses, the current intensity in the stationary state was determined, and from this the "instrument" the oxygen transmis- sibility was obtained. The permeability coefficients of the lenses, corrected for edge effects, were obtained from the slope of the plot of the reciprocal of the transmissibility coefficients versus the lens …
A Deep Insight into Different Acidic Additives as Doping Agents for Enhancing Proton Conductivity on Polybenzimidazole Membranes
2020
[EN] The use of phosphoric acid doped polybenzimidazole (PBI) membranes for fuel cell applications has been extensively studied in the past decades. In this article, we present a systematic study of the physicochemical properties and proton conductivity of PBI membranes doped with the commonly used phosphoric acid at different concentrations (0.1, 1, and 14 M), and with other alternative acids such as phytic acid (0.075 M) and phosphotungstic acid (HPW, 0.1 M). The use of these three acids was reflected in the formation of channels in the polymeric network as observed by cross-section SEM images. The acid doping enhanced proton conductivity of PBI membranes and, after doping, these conducti…
Effect of metallacarborane salt H[COSANE] doping on the performance properties of polybenzimidazole membranes for high temperature PEMFCs
2020
[EN] In this paper, a series of composite proton exchange membranes comprising a cobaltacarborane protonated H[Co(C2B9H11)(2)] named (H[COSANE]) and polybenzimidazole (PBI) for a high temperature proton exchange membrane fuel cell (PEMFC) is reported, with the aim of enhancing the proton conductivity of PBI membranes doped with phosphoric acid. The effects of the anion [Co(C2B9H11)(2)] concentration in three different polymeric matrices based on the PBI structure, poly(2,2 '-(m-phenylene)-5,5 '-bibenzimidazole) (PBI-1), poly[2,2 '-(p-oxydiphenylene)-5,5 '-bibenzimidazole] (PBI-2) and poly(2,2 '-(p-hexafluoroisopropylidene)-5,5 '-bibenzimidazole) (PBI-3), have been investigated. The conducti…
Porous structure of Purevision™ versus Focus® Night&Day™ and conventional hydrogel contact lenses
2002
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevision™ (balafilcon A) and Focus®Night&Day™ (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence®), medium (Acuvue®), and high water content (Precision UV®) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO2, and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observe…
Electric Conductivity Study of Porous Polyvinyl Alcohol/Graphene/Clay Aerogels: Effect of Compression.
2022
In this work, poly(vinyl alcohol) (PVOH)/graphene (GN) oxide/clay aerogels were prepared using montmorillonite (MMT) and kaolinite (KLT) as fillers. This work paves the way for the development of aerogels filled with MMT or KLT with high conductivity. The mechanical properties of the polymer/clay aerogels are enhanced by incorporating GN into these systems. These composite materials have an enhanced thermal stability, and the combination of PVOH and GN leads to interconnected channels which favored the conductivity when a clay (MMT or KLT) is added to the mixed PVOH/GN matrix. However, after compressing the samples, the conductivities drastically decreased. These results show that the desig…
Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges
2021
The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton …
Recent Progress in the Development of Composite Membranes Based on Polybenzimidazole for High Temperature Proton Exchange Membrane (PEM) Fuel Cell Ap…
2020
[EN] The rapid increasing of the population in combination with the emergence of new energy-consuming technologies has risen worldwide total energy consumption towards unprecedent values. Furthermore, fossil fuel reserves are running out very quickly and the polluting greenhouse gases emitted during their utilization need to be reduced. In this scenario, a few alternative energy sources have been proposed and, among these, proton exchange membrane (PEM) fuel cells are promising. Recently, polybenzimidazole-based polymers, featuring high chemical and thermal stability, in combination with fillers that can regulate the proton mobility, have attracted tremendous attention for their roles as PE…
Influence of the anion on diffusivity and mobility of ionic liquids composite polybenzimidazol membranes
2020
[EN] The study of proton conductivity processes has received increasing attention in the past decades due to their potential applications in fields such as electrochemical devices and fuel cells. Despite the high number of composite membranes which have been described for this purpose, fundamental studies of the conduction phenomena in polymeric membranes are scarce. In this article, we study on the effect of the anion on ionic conductivity of ionic liquid composite polybenzimidazole (PBI) membranes. These membranes, which contain 1-butyl-3-methylimidazolium (BMIM) with different counterions ([Cl]-, [NCS]-, [NTf2]- and [BF4]-) were analyzed by electrochemical impedance spectroscopy (EIS) in…
True and Apparent Oxygen Permeabilities of Contact Lenses
1992
We studied the passage of oxygen through some commercially available contact lenses. Oxygen diffusion coefficients were determined by the time-lag method and a 201T Redher permeometer was used to measure the oxygen permeability and transmissibility by the polarographic method. The measurements were carried out at room temperature with 0.09% sodium chloride physiologic solution. The following types of lenses were tested: (1) 12 lenses of cellulose acetate butyrate (CAB) of a mean thickness of 0.194 mm (observed Dk approximately 6.3 barrers) (1 barrier is equivalent to 10(-11) cm3 of O2 (STP).cm2/cm3.s.mm Hg). (2) 13 lenses of a cross-linked polyhydroxyethyl methacrylate (2-HEMA), manufacture…
Ionic Liquid Composite Polybenzimidazol Membranes for High Temperature PEMFC Applications
2019
A series of proton exchange membranes based on polybenzimidazole (PBI) were prepared using the low cost ionic liquids (ILs) derived from 1-butyl-3-methylimidazolium (BMIM) bearing different anions as conductive fillers in the polymeric matrix with the aim of enhancing the proton conductivity of PBI membranes. The composite membranes prepared by casting method (containing 5 wt. % of IL) exhibited good thermal, dimensional, mechanical, and oxidative stability for fuel cell applications. The effects of anion, temperature on the proton conductivity of phosphoric acid-doped membranes were systematically investigated by electrochemical impedance spectroscopy. The PBI composite membranes containin…
Electrical magnitudes in gravitational and centrifugal systems
1993
Abstract A new formulation to study the non-equilibrium processes in gravitational and centrifugal electrochemical systems is developed. The driving forces and the fluxes are measurable quantities. The electrical equilibrium and the pure electrical conduction are described in an evident, simple and exact manner. Theoretical expressions of the emf for several gravitational cells are shown. Some differences are observed with those given in the literature ( eg the terminals density does not appear). The electrochemical potential of ion species is the basic piece in this study.
Enhanced Conductivity of Composite Membranes Based on Sulfonated Poly(Ether Ether Ketone) (SPEEK) with Zeolitic Imidazolate Frameworks (ZIFs)
2018
The zeolitic imidazolate frameworks (ZIFs) ZIF-8, ZIF-67, and a Zn/Co bimetallic mixture (ZMix) were synthesized and used as fillers in the preparation of composite sulfonated poly(ether ether ketone) (SPEEK) membranes. The presence of the ZIFs in the polymeric matrix enhanced proton transport relative to that observed for SPEEK or ZIFs alone. The real and imaginary parts of the complex conductivity were obtained by electrochemical impedance spectroscopy (EIS), and the temperature and frequency dependence of the real part of the conductivity were analyzed. The results at different temperatures show that the direct current (dc) conductivity was three orders of magnitude higher for composite …
Diffusivity and free anion concentration of ionic liquid composite polybenzimidazole membranes.
2021
[EN] In this article, PBI composite membranes containing the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf2) at 1, 5, 10, 20 and 50 wt% (named PBI-IL-x) have been prepared by a casting method. The internal morphology of the membranes was analyzed by scanning electron microscopy (SEM), revealing that the incorporation of IL promotes the formation of porous channels. Thermal and mechanical stability was confirmed by thermogravimetric analysis (TGA) and tensile test measurements. The ionic transport through membranes was analysed by means of electrochemical impedance spectroscopy (EIS), showing a dependence on the IL loading, reaching a highest condu…
Central role of the observable electric potential in transport equations.
2001
Nonequilibrium systems are usually studied in the framework of transport equations that involve the true electric potential (TEP), a nonobservable variable. Nevertheless another electric potential, the observable electric potential (OEP), may be defined to construct a useful set of transport equations. In this paper several basic characteristics of the OEP are deduced and emphasized: (i) the OEP distribution depends on thermodynamic state of the solution, (ii) the observable equations have a reference value for all other transport equations, (iii) the bridge that connects the OEP with a certain TEP is usually defined by the ion activity coefficient, (iv) the electric charge density is a non…
New method to determine the true transmissibilities and permeabilities of oxygen in hydrogel membranes
1999
In the present paper, an electrochemical method to obtain the true transmissibilities and permeabilities of hydrogels to oxygen is proposed. The method involves the measurement of the electric current arising from the flow of oxygen through a potentiostat cell integrated by a top water layer, the hydrogel membrane, and a thin water layer between the membrane and the cathode, where the oxygen is reduced. Varying the thickness of the top water layer, the true permeation characteristics of the hydrogels are obtained. A parallel study was carried out in which the transmissibilities and permeation coefficients were obtained from the variation of the steady state current with the thickness of the…
Hydrogen Production from Methanol-Water Solution and Pure Water Electrolysis Using Nanocomposite Perfluorinated Sulfocationic Membranes Modified by P…
2022
In this work, we report the preparation of Nafion membranes containing two different nanocomposite MF-4SC membranes, modified with polyaniline (PANI) by the casting method through two different polyaniline infiltration procedures. These membranes were evaluated as a polymer electrolyte membrane for water electrolysis. Operating conditions were optimized in terms of current density, stability, and methanol concentration. A study was made on the effects on the cell performance of various parameters, such as methanol concentration, water, and cell voltage. The energy required for pure water electrolysis was analyzed at different temperatures for the different membranes. Our experiments showed …
Phosphoric Acid Doped Polybenzimidazole (PBI)/Zeolitic Imidazolate Framework Composite Membranes with Significantly Enhanced Proton Conductivity unde…
2018
The preparation and characterization of composite polybenzimidazole (PBI) membranes containing zeolitic imidazolate framework 8 (ZIF-8) and zeolitic imidazolate framework 67 (ZIF-67) is reported. The phosphoric acid doped composite membranes display proton conductivity values that increase with increasing temperatures, maintaining their conductivity under anhydrous conditions. The addition of ZIF to the polymeric matrix enhances proton transport relative to the values observed for PBI and ZIFs alone. For example, the proton conductivity of PBI@ZIF-8 reaches 3.1 10&minus
Oxygen permeability of hydrogel contact lenses with organosilicon moieties
2002
Oxygen transport through two extended wear (day and night) hydrogel contact lenses that contain organosilicon moieties (balafilcon A and lotrafilcon A) was studied in the hydrate (hydrogel) and dry (xerogel) states. The water uptake increased the oxygen permeability [(Dk)app] and transmissibility [Dk/L(av)] coefficients of the dry materials by about 70%. The (Dk)app for the hydrated lenses was determined following the so-called stack procedure. The values obtained were 107 +/- 4 barrer for balafilcon A and 141 +/- 5 barrer for lotrafilcon A, about 5-10 times larger than those previously reported for conventional (without organosilicon moieties) extended wear hydrogels contact lenses. The Dk…
Wind gustiness and sulphur dioxide concentration in the urban area of Barcelona, Spain
1991
Abstract Data on aerosols and wind parameters recorded at the Barcelona Meteorological Observatory were analysed to determine their relation to wind gustiness, defined according to the criteria used at Brookhaven National Laboratory. The relation between wind gustiness and wind speed and direction was analysed, together with the annual and monthly variation. The relation between the concentration of sulphur dioxide and wind gustiness was also investigated, and proved to be a very useful indicator in this kind of analysis, especially in local studies.
Proton Conducting Electrospun Sulfonated Polyether Ether Ketone-Graphene Oxide Composite Membranes
2017
[EN] A series of novel composite membranes, based on sulfonated poly(ether ketone) (SPEEK) with a graphene oxide (GO) layer, were prepared. One contained a GO layer sandwiched between the SPEEK-polyvinyl alcohol (PVA) matrix (SPEEK/PVA@GO), and another deposited thin layers of GO on the nanofibers of SPEEK-polyvinyl butyral (PVB), with both sandwiched in the phase matrix of SPEEK-PVA (SPEEK/PVA@GO-NF). Various nanofiber thicknesses were studied by varying the electrospinning time. The prepared composite membranes with different nanofiber thicknesses were characterized by scanning electron microscopy, water uptake, ionic exchange capacity, thermogravimetric analysis, mechanical properties an…
Thermodynamics of electrokinetic processes—I. Formulations
1990
Abstract The phenomenological equations of electrokinetic processes are studied according to five different formulations. Transformation matrices with Haase's formulation are given. A study of the measurable character of fluxes, forces and phenomenological coefficients in those formulations is also made. The extrinsic character, if so, of the formulations is examined and a general definition of formulations established only for binary solutions is given. Finally, a review of the literature is included, aiming to clarify the possible misunderstandings arising from the application of these five formulations.
Structural and Electrochemical Analysis of CIGS: Cr Crystalline Nanopowders and Thin Films Deposited onto ITO Substrates
2021
A new approach for the synthesis of nanopowders and thin films of CuInGaSe2 (CIGS) chalcopyrite material doped with different amounts of Cr is presented. The chalcopyrite material CuInxGa1 − xSe2 was doped using Cr to form a new doped chalcopyrite with the structure CuInxCryGa1 − x − ySe2, where x = 0.4 and y = 0.0, 0.1, 0.2, or 0.3. The electrical properties of CuInx CryGa1 − x − ySe2 are highly dependent on the Cr content and results show these materials as promising dopants for the fabrication thin film solar cells. The CIGS nano-precursor powder was initially synthesized via an autoclave method, and then converted into thin films over transparent substrates. Both crystalline precursor p…
Biological oxygen apparent transmissibility of hydrogel contact lenses with and without organosilicon moieties.
2003
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact le…
Proton Transport in Membranes Prepared from Sulfonated Polystyrene-Poly(vinylidene fluoride) Blends
2001
The preparation of new cation-exchange membranes from polymer composites based on poly(vinylidene fluoride), sulfonated polystyrene-co-divinylbenzene, and antimonic acid is reported. The thermal properties of the composites have been characterized by differential scanning calorimetry. Values of the transport number of protons in the membranes were obtained from the observable electric potential. It is defined from the potential difference measured between the electrodes reversible to one of the constituent ions in equilibrium with the system. When compared with Nafion cation-exchange membranes, the membranes described in this work exhibit interesting proton transport properties that could m…
Determination of the glass transition temperature of poly(cyclohexyl acrylate) from oxygen permeability measurements
1993
Abstract The glass transition temperature ( T g ) of poly(cyclohexyl acrylate) (PCA) has been obtained from measurements of the oxygen permeability ( P = 0.60 barrers, T g = 23.5 ± 2.0°C) using a potentiostatic electrochemical sensor, and from the oxygen diffusion coefficient ( D = 0.12 × 10 −8 cm 2 s −1 , T g = 24.0 ± 1.8°C) by the time-lag method. A T g of 25 ± 1°C was found by differential scanning calorimetry and a T g of 25.0 ± 3.5°C was obtained from the specific volume by dilatometry. The fractional free volume ( v f ) at T g is 0.020 ± 0.002, which is slightly below (∼ 20%) most glassy polymers. A linear correlation has been observed between ln D and the reciprocal of v f , which su…