▎ 摘　　要

The interfacial structures of a Nafion/graphene composite, which is used tomimic the interfaces of the catalyst layer in proton-exchange membrane fuel cells (PEMFCs),under different humid environments, are investigated by sum-frequency generation (SFG)vibrational spectroscopy. The Nafion thinfilm seems to form a lamellar structure on thegraphene surface where the sulfonate moieties of Nafion at the buried graphene surfaceprobably orientate to the Nafion bulk, the same as that of the free Nafion/air interface. The SFGobservation shows that the structure of the buried Nafion/graphene interface is distinct fromthat on a buried hydrophilic substrate surface such as fused quartz (SiO2) and calciumfluoride (CaF2). The structural differences inthe buried Nafion/graphene interfaces significantly affect water adsorption behaviors at the interface. This new information promisesto alleviate some of the significant problems in modeling the PEMFC system.