40SiO2–40P2O5–20ZrO2 sol-gel infiltrated sSEBS membranes with improved methanol crossover and cell performance for direct methanol fuel cell applications

Abstract

40P 2 O 5 -20ZrO 2 sol-gel infiltrated sSEBS membranes with improved methanol crossover and cell performance for direct methanol fuel cell applications Abstract Membranes commonly used in direct methanol fuel cell (DMFC) are expensive and show a great permeability to methanol which reduces fuel utilization and leads to mixed potential at the cathode.In this work, sulfonated styrene-ethylene-butylene-styrene (sSEBS) modified membranes with zirconia silica phosphate sol-gel phase are developed and studied in order to evaluate their potential use in DMFC applications. The synthesized hybrid membranes and sSEBS are subjected to an exhaustive physicochemical characterization by liquid uptake, ion exchange capacity, atomic force microscopy, X-ray photoelectron spectroscopy and dynamic mechanical and thermogravimetric analyses. Likewise, the potential use of the prepared membranes in DMFC is evaluated by means of electrochemical characterizations in single cell, determining the limiting methanol crossover current densities, proton conductivities and DMFC performances. The hybrid membranes show lower water and methanol uptakes, higher stiffness, water retention capability, upper power density and lower methanol crossover than sSEBS and Nafion 112.

Charge transfer mechanisms in 40SiO2-40P2O5-20ZrO2 /sulfonated styrene-ethylene-butylene-styrene hybrid membranes for low temperature fuel cells

“…Fig. 9 also displays the maximum power density values obtained when these hybrid membranes are used as electrolytes in a DMFC [37]. A quick comparison with other published data shows that the maximum power density values offered by sSEBS-Zr10 for PEMFCs and sSEBS-Zr40 for DMFCs are in line with the…”

“…Regarding DMFC, the polarization curve measurements were conducted at 333 K supplying 1 M methanol solution at 3 mL min − 1 and pure humidified oxygen at 100 mL min − 1 and 1 bar to anode and cathode, respectively. More information about the electrochemical characterization of membrane-electrodes assemblies can be found elsewhere [36,37]. Consequently, the two membranes with better performance are the ones where the ion diffusivity maintains their coupling with the molecular processes.…”

“…The activation energy (E a ) for the σ DC of the sSEBS and sSEBS-Zr membranes. values exhibited by Nafion 117 and other polymers measured at the same temperature, respectively [36,37,[53][54][55][56].…”

“…Accordingly, C. del Río et al [36] studied a series of novel and low-cost hybrid membranes using zirconia modified phosphosilicate and sSEBS as the polymeric matrix developed via sol-gel chemistry and direct infiltration method. These hybrid membranes were previously tested in both Hydrogen and Methanol single cells showing interesting performances, finding the best results at different infiltration times depending on the fuel used [36,37]. Thus, in PEMFC the better power density was reached for the membrane infiltrated for 10 min while an infiltration time of 40 min was necessary for better results in DMFC.…”

High-Performance Proton Exchange Membrane of Sulfonated Polystyrene-b-polyisobutylene-b-polystyrene

“…42,52,55 The power density of the uncross-linked SSEBS membrane used in DMFCs was measured to be 15 mW•cm −2 in the literature. 56 On the other hand, it is recognized that there are inherent drawbacks of SSEBS as a PEM. 52,57,58 The poor oxidation stability of SSEBS was caused by the tertiary carbon of the butene structure in EB soft segments along the SSEBS macromolecular chains.…”