Microphase separated hydroxide exchange membrane synthesis by a novel plasma copolymerization approach

Hydroxide exchange membrane (HEM) is the most important and key performance-limiting component of HEMFC. Plasma copolymerization is adopted to synthesize the hydroxide exchange membranes with microphase-separated structure. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy demonstrate that the quaternary ammonium groups can be successfully introduced into the polymer matrix in the plasma copolymerization process. The transmission electron microscope images reveal that plasma copolymerization allowed the generation and aggregation of ionic groups and the formation of ionic transport channels, leading to an excellent phase-separated morphology of the membrane. The plasma-copolymerized hydroxide exchange membranes possess excellent hydroxide ion conductivity, chemical and thermal stability, ultra-thin and mechanical integrity structure, as well as the ability of building an efficient three-phase-boundary, making them very exiting candidates for fuel cell applications.

Graphical abstract. Plasma copolymerization has been successfully demonstrated in the hydroxide exchange membrane synthesis. The plasma copolymerization allowed the generation and aggregation of ionic groups and the formation of ionic transport channels, leading to an excellent phase-separated morphology of the membrane. The plasma-copolymerized hydroxide exchange membranes possess excellent hydroxide ion conductivity, chemical and thermal stability, ultra-thin structure, as well as the ability of full encompassing the catalyst particles without the need of solubilizing the polymer in low boiling point water-soluble solvents, making them very exiting candidates for fuel cell applications.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Quaternary ammonium groups can be introduced into the polymer matrix by plasma copolymerization. ► The content of the quaternary ammonium groups in plasma-copolymerized membrane (PCPNCl) is up to 2.41 at.%. ► Plasma copolymerization allowed the aggregation of ionic groups and the formation of ionic transport channels. ► The hydroxyl ion conductivity of plasma copolymerized hydroxide exchange membrane is 13.7 mS cm−1 in deionized water at 20 °C.