Abstract
Nano-silicon dioxide (SiO2) was incorporated into the matrix of sulfonated poly(ether ether ketone) (SPEEK)/ammonium ionic liquid (AIL) membranes by solution casting, with the aim of reducing ionic liquid leaching and any consequent decrease in proton conductivity. Fourier transform infrared (FTIR) spectra results indicate incorporation of the SPEEK matrix with AIL and nano-SiO2. Scanning electron microscopy (SEM) and X–ray diffraction (XRD) images revealed that incorporation of nano-SiO2 make the ternary composite membranes more flexible. The maximum ion exchange capacity (IEC) value was 3.25 meq/g, and the net structure formed by the nano-SiO2 not only retarded AIL leaching, but also increased the proton conductivity of the composite membranes. AIL leaching from the membranes was between 20% and 30%, which was lower than that of the SPEEK/AIL membrane. The maximum proton conductivity for the SPEEK/AIL/SiO2 membranes reached 10.73 mS/cm at 393 K.
Highlights
Fuel cells offer high power densities and energy conversion efficiencies, and produce limited amounts of environmental pollution; they are considered to be clean energy sources that have the potential to replace fossil fuels [1]
The chemical structures of PEEK, sulfonated poly(ether ether ketone) (SPEEK)–75, ammonium ionic liquid (AIL), and SPEEK–75/AIL/SiO2 composite peak of pristine PEEK was confirmed at 1492 cm−1, and this demonstrates the existence of a C−C
Fourier transform infrared (FTIR) spectra results indicated that the SPEEK matrix had been incorporated with AIL and
Summary
Fuel cells offer high power densities and energy conversion efficiencies, and produce limited amounts of environmental pollution; they are considered to be clean energy sources that have the potential to replace fossil fuels [1]. As ionic liquids (IL) possess certain merits, such as high proton conductivity, low viscosity, negligible vapor pressure, and good electrochemical and thermal stability [19], other researchers [20,21] have attempted to incorporate IL within the SPEEK matrix to enhance membrane proton conductivity. In this respect, the proton conductivity of a SPEEK/alkylimidazolium membrane reaches 3.16 mS/cm under anhydrous conditions at 418 K, and the highest power density of the PEMFC using the prepared membrane reaches 203 mW/cm at 418 K [21]. The electrochemical characteristics of the SPEEK/AIL/SiO2 composite membranes, such as IEC, proton conductivity, and AIL leaching, were analyzed
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