Low-acidity polymer electrolyte membranes are essential to polymer electrolyte fuel cells (PEFCs) and water electrolysis systems, both of which are expected to be next-generation energy and hydrogen sources. We developed a new type of highperformance polymer electrolyte membrane (PEM) in which the core particles are precisely electrolyte polymer coated and filled into binder resin. Cellulose nanocrystals (CNCs), which have attracted attention as light, rigid, and sustainable materials, were selected as the core material for the filler. The CNC surface was coated with a new block copolymer containing a proton conductive polymer of poly(vinylphosphonic acid) (PVPA) and a hydrophobic polymer of polystyrene (PS) using RAFT polymerization with particles (PwP) we developed. The pelletized fillers and the filler-filled polycarbonate membranes achieved proton conductivities of over 10 −2 S/cm with lower activation energies and much weaker acidity than the Nafion membrane.

Polymer electrolyte fuel cells are attracting attention as clean, highly efficient power generation devices that can solve problems such as energy resource depletion, global warming, and environmental pollution. In this research, we have fabricated proton conductive filler-filled membranes, employing polymer-coated cellulose nanocrystals and different binder resins. Moreover, we have demonstrated the relationship between proton conductivity and water uptake of binder resins. It was clarified that the fabricated membrane with a high water uptake ratio showed excellent proton conduction performance under high humidity at low temperatures with a low activation energy for proton conduction. The substantiation of the compatibility relationship between water absorption and efficacy of proton conduction can contribute to the design and fabrication of a new binder resin synthesis model and contributes to the knowledge of the polymer skeleton structure for the improvement of the proton conductive performance of polymer electrolyte membranes.

Proton exchange membrane (PEM) is the main component that determines the performance of polymer electrolyte fuel cells. The construction of proton-conduction channels capable of fast proton conduction is an important...

Polymer electrolyte membrane fuel cells (PEMFC) have the challenges of operation under low humidity conditions caused by the proton conduction mechanism dependent on water. We focused on polymeric ionic liquids (PIL), which are promising for high proton conductivity under the wide range environment because of having the characteristic of the polymer electrolyte liquid. However, it is difficult to fabricate the self-standing membrane of PIL due to the high hygroscopicity and fluidity. In this paper, to inhibit the fluidity of PIL developing the self-standing polymer electrolyte membrane (PEM), the hydrophobic chain segment of styrene is inserted between PIL of poly(vinylphosphonic acid/1-propylimidazole) (P(VPA/1PIm)) by RAFT polymerization. The synthesized sample of P(VPA/1PIm)-block-polystyrene (P(VPA/1PIm)-b-PS) is potentially applicable to PEM materials because it is obtained in a powder state, having the high heat resistance of up 300°C, and performing the proton-conducting property under the wide range environment.

Proton conduction in the current polymer electrolyte membrane depends on water molecules, which necessitates high-humidity environments. On the contrary, proton conduction in low-humidity environments has been required for expanding operation conditions of polymer electrolyte fuel cells. Recently, ionic liquids (ILs) have been focused on novel proton conductive materials, however, the ILs were hard to fabricate the self-standing membrane owing to their fluidity. In this paper, we have developed composite materials composed of ILs and inorganic nanoparticles by coating ILs as polymer states (PILs) on the surface of nanoparticles. Notably, this material has obtained a powder form, and we have succeeded in suppressing the fluidity of ILs. The PILs-coated nanoparticles have achieved good proton conductivity over 10-2 S cm-1 at 95%RH, also indicated over 10-4 S cm-1 under 60%RH. In addition, we have clarified the relationship between the thickness of PILs and proton conductivities.