Source: Journal of Power Sources
Volume: 258 Pages: 351-355
Published: Jul (2014)
Linear perfluoropolyether (PFPE) peroxide was used to confer superhydrophobic surface properties to gas diffusion layer (GDL) by means of direct functionalization of a GDL based on carbon cloth (CC) material. The thermal decomposition of a linear PFPE peroxide produces linear PFPE radicals that covalently bond the unsaturated moieties on the surface. Perfluorinated radicals are directly and covalently bound to the carbonaceous structure of the CC without any spacer that could decrease both thermal and chemical stability of the GDL. The obtained CC hydrophobicity exceeded the superhydrophobicity threshold and was enduringly stable. The relationship between the linkage of fluorinated chains and the variations of surface chemical?physical properties were studied combining X-ray photoelectron spectroscopy (XPS), resistivity measurements, scanning electron microscopy (SEM) and contact angle measurements. Despite the excellent insulating properties of the PFPE polymer, the functionalized carbonaceous materials substantially retained their conductive properties. The PFPE-modified GDLs were tested in a single fuel cell at the lab scale. The cell tests were run at two temperatures (60C and 80C) with a relative humidity (RH) of hydrogen and air feeding gases equal to 80/100% and 60/100%, respectively.
Author(s): TALAEEMASHHADI S.; SANSOTERA M.; GAMBAROTTI C.; FAMULARI A.; BIANCHI C. L.; GUARDA P. A.; NAVARRINI W.
Volume: 59 Pages: 150-159
DOI: 10.1016/j.carbon.2013.03.003 Published: AUG 2013
Multi-walled carbon nanotubes (MWCNTs) have been functionalized through perfluoropolyether (PEPE) radicals obtained by thermal decomposition of linear PFPE peroxide. The reactivity of MWCNTs with PFPE peroxide has been compared with the direct fluorination of MWCNTs using elemental fluorine in mild conditions. The experimental results indicated that the functionalization with PFPE peroxide and the direct fluorination with elemental fluorine were suitable techniques to modify and control the physical-chemical properties of MWCNTs. After the introduction of PFPE chains on the MWCNT surface, the wettability of MWCNTs changed from hydrophilic to superhydrophobic, because the low surface energy properties of PFPE were transferred to the MWCNT surface. However, the linkage of PFPE chains weakly influenced the electrical properties of conductive MWCNTs. The amount of PFPE chains linked to the carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE have been evaluated by mass balance. The modified MWCNTs have been characterized by X-ray photoelectron spectroscopy, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, contact angle and surface area measurements. The effects of the chemical treatment on the conductive properties of MWCNTs have been studied by resistivity measurements at different applied pressures.
Source: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Volume: 37 Issue:7 Pages: 6277-6284
The thermal decomposition of a linear perfluoropolyether peroxide produced perfluoropolyether radicals that covalently bonded the unsaturated moieties on the surface of carbon black and carbon cloth. Measurements of contact angles demonstrated that water droplets were enduringly stable on the treated materials and that contact angle values were significantly high, exceeding the superhydrophobicity threshold. On the contrary, the droplets were adsorbed in few seconds by the native materials. Conductivity measurements showed that the covalent linkage of fluorinated chains weakly modified the electrical properties of the conductive carbonaceous materials, even if the surface properties changed so deeply. The relationship between the linkage of fluorinated chains and the variations of physical-chemical properties were studied combining X-ray photoelectron spectroscopy, resistivity measurements, scanning electron microscopy and surface area analysis. The modified carbon cloth was also tested out as gas-diffusion layer in a fuel cell and preliminary results were recorded.