In Situ Observation of Thermal Proton Transport through Graphene Layers

Protons can penetrate through single-layer graphene, but thicker graphene layers (more than 2 layers), which possess more compact electron density, are thought to be unfavorable for penetration by protons at room temperature and elevated temperatures. In this work, we developed an in situ subsecond time-resolved grazing-incidence X-ray diffraction technique, which fully realizes the real-time observation of the thermal proton interaction with the graphene layers at high temperature. By following the evolution of interlayer structure during the protonation process, we demonstrated that thermal protons can transport through multilayer graphene (more than 8 layers) on nickel foil at 900 °C. In comparison, under the same conditions, the multilayer graphenes are impermeable to argon, nitrogen, helium, and their derived ions. Complementary in situ transport measurements simultaneously verify the penetration phenomenon at high temperature. Moreover, the direct transport of protons through graphene is regarded as...