"Straw in the Clay Soil" Strategy: Anticarbon Corrosive Fluorine-Decorated Graphene Nanoribbons@CNT Composite for Long-Term PEMFC.

Carbon corrosion poses a significant challenge in polymer exchange membrane fuel cells (PEMFCs), leading to reduced cell performance due to catalyst layer degradation and catalyst detachment from electrodes. A promising approach to address this issue involves incorporating an anticorrosive carbon material into the oxygen reduction reaction (ORR) electrode, even in small quantities (≈3 wt% in electrode). Herein, the successful synthesis of fluorine-doped graphene nanoribbons (F-GNR) incorporated with graphitic carbon nanotubes (F-GNR@CNT), demonstrating robust resistance to carbon corrosion is reported. By controlling the synthesis conditions using an exfoliation method, the properties of the composite are tailored. Electronic structural studies, employing density functional theory (DFT) calculations, to elucidate the roles of fluorine dopants and graphitic carbon nanotubes (CNTs) in mitigating carbon corrosion are conducted. Physicochemical and electrochemical characterization of F-GNR@CNT reveal its effectiveness as a cathode additive at the single-cell scale. The addition of F-GNR@CNT to the Pt/C cathode improves durability by enhancing carbon corrosion resistance and water management, thus mitigating the flooding effect through tailored surface properties. Furthermore, advanced impedance analysis using a transmission line model is performed to gain insights into the internal resistance and capacitive properties of electrode structure.

Experimental and Computational Approaches to Sulfonated Poly(arylene ether sulfone) Synthesis Using Different Halogen Atoms at the Reactive Site.

Engineering thermoplastics, such as poly(arylene ether sulfone), are more often synthesized using F-containing monomers rather than Cl-containing monomers because the F atom is considered more electronegative than Cl, leading to a better condensation polymerization reaction. In this study, the reaction's spontaneity improved when Cl atoms were used compared to the case using F atoms. Specifically, sulfonated poly(arylene ether sulfone) was synthesized by reacting 4,4'-dihydroxybiphenyl with two types of biphenyl sulfone monomers containing Cl and F atoms. No significant difference was observed in the structural, elemental, and chemical properties of the two copolymers based on nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and electrochemical impedance spectroscopy. However, the solution viscosity and mechanical strength of the copolymer synthesized with the Cl-terminal monomers were slightly higher than those of the copolymer synthesized with the F-terminal monomers due to higher reaction spontaneity. The first-principle study was employed to elucidate the underlying mechanisms of these reactions.