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Preparation of Nafion/various Pt-containing SiO₂ composite membranes sulfonated via different sources of sulfonic group and their application in self-humidifying PEMFC

Yang, H.N., Lee, D.C., Park, S.H., Kim, W.J.
Journal of membrane science 2013 v.443 pp. 210-218
X-ray diffraction, X-ray photoelectron spectroscopy, artificial membranes, electrolytes, nanoparticles, oxidation, particle size, relative humidity, silica, sodium sulfate, sulfuric acid, transmission electron microscopes
Pt nanoparticles were successfully deposited onto SiO₂ nanoparticles sulfonated by different chemical sources such as H₂SO₄, CH₃SO₃H, Na₂SO₄, and HSO₃Cl and denoted as Pt-HS/SiO₂, Pt-CS/SiO₂, Pt-NS/SiO₂ and Pt-SS/SiO₂, respectively. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analyses for Pt-containing sulfonated SiO₂ nanoparticles were conducted to identify the phase, oxidation state of Pt incorporated and the existence of –SO₃ ⁺ on SiO₂ nanoparticles. Transmission electron microscope analysis shows 2–4nm of Pt nanoparticles on the surface of SiO₂ nanoparticle. The proton conductivities of various membranes are highly consistent with metallic Pt and –SO₃ ⁺ contents based on XPS analysis. The membrane electrolyte assembly (MEA) fabricated with Nafion/Pt-NS/SiO₂ composite membrane showing the smallest Pt particle size and excellent dispersion shows the best cell performance under zero humidity, following the order of Pt-NS/SiO₂>Pt-HS/SiO₂>Pt-CS/SiO₂>Pt-SS/SiO₂. It also shows that the MEA fabricated with Nafion/Pt-NS/SiO₂ composite membrane shows the least decrease by 5.7% in open circuit voltage with relative humidity while that for Nafion/Pt-CS/SiO₂ composite membrane is the largest by 15.3%. The results suggest that Pt particle size, its dispersion, metallic Pt and –SO₃ contents are critical and quite different with chemical source for sulfonation, affecting the cell performance.