Development of a Heat-Treated Polymer–Polymer Type Charge-Transfer Blend Membrane for Application in Polymer Electrolyte Fuel Cells

Abstract

We developed polymer electrolyte membranes (PEMs) utilizing charge-transfer (CT) interactions for polymer electrolyte fuel cells (PEFCs). CT complex formation was applied to control the position of proton conductive groups in the membranes. To understand the effect of CT complex formation on PEM performance, heat treatment was performed to enhance the extent of CT complex formation in the membrane. In this work, sulfonated polyimide (SPI) was used as the electron-accepting polymer, while polyether-containing electron-rich dialkoxy­naphthalene (Poly-DAN) was used as the electron-donating polymer. After heat treatment at 150 °C for 50 h, the concentration of CT complex in the membrane was significantly enhanced by about 13 times. Heat-treated SPI/Poly-DAN membranes showed higher mechanical strength (50.8 MPa) than Nafion 212 (15.5 MPa) and highly chemical durability compared to the untreated membrane by the synergetic effect of enhanced CT complex formation and chemical cross-linking. Heat-treated SPI/Poly-DAN membranes also showed reasonable proton conductivity (32.3 mS cm–1, 80 °C, and 90% RH), although some cross-linking occurred between sulfonic acid units due to the heat treatment process. In single cell tests, heat-treated SPI/Poly-DAN membranes had maximum power densities of 255 mW cm–2 at 80 °C and 95% RH and 59.0 mW cm–2 at 110 °C and 31% RH, indicating that these heat-treated CT complex membranes could be used for fuel cell applications.

Magnetic Field-Induced Through-Plane Alignment of the Proton Highway in a Proton Exchange Membrane

“…Accordingly, the through-plane (TP) membrane conductivity should be high to obtain high power performance of corresponding electrochemical cells. Increasing the connectivity or volume of the water channel has been a major direction for enhancing the proton conductivity of the membrane, and this has been achieved by structural design of polymer electrolytes and the hydrophilic additives. − …”

Cosolvent-Driven Interfacial Polymerization for Superior Separation Performance of Polyurea-Based Pervaporation Membrane

“…This amino carbonic acid would react further with alkyl amine radicals of PEI to form urea linkage [18,39,40]. Moreover, curing or heat treatment may also cause chargetransfer-complex in polyurea, which is an intra-and inter-molecular interaction between the benzene rings (electron-donating groups), resulting in a more compact layer [41]. The water concentration in the permeate reached 98.8 ± 0.3 wt.% (α A/B = 741) when the curing temperature was 50 • C. At a temperature higher than 50 • C, the change in water concentration in the permeate was not significant.…”

Silicone‐containing polymer blend electrolyte membranes for fuel cell applications

“…On this basis, we have attempted to develop polymer blends of silicone and hydrocarbon polymers, in order to enhance the merits whilst suppressing the demerits of silicone‐based PEMs (Scheme 1). In particular, we have taken advantage of the formation of charge‐transfer (CT) complexes to prepare intimately mixed polymer‐blend PEMs whilst avoiding phase separation 29–32 . Such CT polymer blends are composed of two different polymers ‐ one contains electron‐donating units, whilst the other contains electron‐accepting units 29,31,32 .…”

“…In particular, we have taken advantage of the formation of charge‐transfer (CT) complexes to prepare intimately mixed polymer‐blend PEMs whilst avoiding phase separation 29–32 . Such CT polymer blends are composed of two different polymers ‐ one contains electron‐donating units, whilst the other contains electron‐accepting units 29,31,32 . The donor and acceptor polymers can align alternatively due to the CT interaction, resulting in the preparation of a miscible polymer blend at the molecular level.…”

“…The donor and acceptor polymers can align alternatively due to the CT interaction, resulting in the preparation of a miscible polymer blend at the molecular level. In addition, the CT polymer blend method can be used to control several properties such as mechanical strength and the T g 29,31,32 …”