图1. Schematic of the synthesis of Nafion/nanoporous graphene/Nafion. a) CVD graphene on copper substrate (centimeter scale, actual size 3 × 3 cm²); b) plasma treatment on copper substrate; c) D520 spin-coating; d) N212 hot-press; e) copper etching in FeCl₃; f) air-dried nanoporous graphene on N212; g) another D520 spin-coating on the graphene side; h) another N212 hot-press (actual size 3 × 3 cm²).

图2. Characterization of CVD graphene and the composite N/G/N membrane. a) SEM of graphene on SiO₂/Si, rectangles indicate the areas for Raman characterization in b); b) Raman spectra of graphene on SiO₂/Si substrate; c) SEM of graphene on N212; d) cross section SEM of N/G/N membrane; e) contact angle of N212; f) contact angle of N212 with graphene transferred; g) photograph of the composited N/G/N membrane; h) photograph of the composited MEA.

图3. Characterization of the perforated graphene. a) photograph of the plasma treating process (left: Ar 20W; right: O₂ 7W with homemade Faraday cage); b) Raman spectra of perforated graphene; c) Defect density analysis from the Raman spectra in b).

图5. Polarization curve of N212/nanoporous graphene/N212 composite membranes in 60 °C DMFC.

图6. Fuel cell performance comparison of N212/nanoporous graphene/N212 composite membranes.

图7. Voltage degradation of best-performed N/G O10 s/N and commercial N115 at 0.08 mA cm⁻², 60 °C.

图8. Water distribution analysis at the interfacial regions of Nafion/nanoporous graphene/Nafion composite membranes (grey dots indicate the position of graphene layer). a1, a2) bulk Nafion (λ = 20); b1, b2) Nafion/pristine graphene/Nafion; c1, c2) Nafion/H decorated nanoporous graphene/Nafion; d1, d2) Nafion/epoxy decorated nanoporous graphene/Nafion; e1, e2) Nafion/hydroxyl decorated nanoporous graphene/Nafion; f) Layer-to-layer distribution functions analysis between atoms in water molecule and graphene; g) Layer-to-layer distribution functions analysis between atoms in Nafion and graphene.